Monthly Archives: April 2015

Blowout Blues and My Friend Murphy

April 29, 2015

This week saw a return to the job site after spending ALL of last week catching up on the bookkeeping and preparing our taxes.  I was a lot further behind than I thought and had not reconciled the accounts since last August.  I also had some technical hurtles associated with the QuickBooks file crash in May of last year. But all were concurred and I finished off on Saturday and actually took Sunday off (first in a very long time).

This meant Monday was the return to the site where I started to strip the forms.  The forms came off quite easily and were not too time consuming considering the number of screws involved.  What was a surprise was the number of snapped screws including the #14 x 3.5″ ones used to attached the vertical supports and 2×2 cleats holding on the bottom edge of the plywood forms. At least this showed they were holding fast into the ICF, but if I had not used as many fasteners as I did, we probably would have had a lot more problems.

It takes a lot of force to snap these #14 screws!

It takes a lot of force to snap these #14 screws!

As I stripped off the forms, all looked pretty good until I got to the North wall and then it became apparent that I had actually had a fairly significant form blowout that was going to cause me problems.  It was the perfect storm with the following contributing factors:

– Because this wall has the basement to ground floor stairs running along its length, there was requirements for the 20M rebar that was running horizontally through the 9th row of ICF.  This meant the ICF was cut down and therefore the height of the plywood formed curb on this wall was about 12″ taller than any other wall (representing a lot more form pressure).

– I had originally made a mistake when forming this wall.  The fix had a 6″ tall strip of plywood seamed along the top edge of the inboard plywood panels.  This created a weakness in the forms.

– Further compounding this weakness was the fact that I completely forgot to brace some of the seam and also forgot to screw some of the plywood to the whalers in this area.

– This was the wall that the placing crew attempted to use a vibrator to ensure concrete was flowing around the profiles of the plywood formed top curb.  After seeing some movement in the forms, this task was skipped for the rest of the foundation.  Even then, from the exterior of the forms, the full extent of the blowout was not clear.

– For some reason, the plywood delaminated in this area and concrete was flowing BETWEEN the laminate layers of the plywood further reducing the strength of the already stressed 1/2″ Ply.

Plywood delaminated and 'bubbled' allowing the concrete to flow between the laminate layers.

Plywood delaminated and ‘bubbled’ allowing the concrete to flow between the laminate layers..

Delaminated plywood - this must of been caused by a defective glue joint getting wet, but I believe is a pretty rare phenomenon.

Delaminated plywood – this must of been caused by a defective glue joint getting wet, but I believe is a pretty rare phenomenon.

This is where Murphy and his law stepped in – Out of every wall in the house, this is the one and ONLY wall where a blow out mattered.  I do not have a stud wall in the basement beside the stair opening.  I plan to attach the drywall directly to the ICF and of course it needs to be continuous and line up with the drywall on the first storey.  SO, I would have no means of furring out around a blowout this large (3+” at its worse).

Only one thing left to do – chip it away and it was best to do now while the concrete was still fairly green and would chip away easily.  A 4 hour rental from the local tool shop and the blowout was a distant memory (OK not so distant – I had the blisters as a nice parting memento).

A blowout in the worst place possible.  Not a structural concern, but would have reduced allowable stair width meaning I would not comply with the SaferHomes program.

A blowout in the worst place possible. Not a structural concern, but would have reduced allowable stair width meaning I would not comply with the SaferHomes program.

4 Hours of persistant chipping and the blowout had been removed.  I will probably leave in this rough surface as all will be covered with either rim boards or drywall.

4 Hours of persistent chipping and the blowout had been removed. I will probably leave in this as a rough surface as all will be covered with either rim boards or drywall.

On a positive note, I removed one of the beam pocket plugs and these turned out perfectly.

On a positive note, I removed one of the beam pocket plugs and these turned out perfectly.

Over the next day or so I will finish stripping the forms.  I then will need to do a massive cleanup of the pit floor (stack all lumber and whatnot on the scaffold cross ties so nothing is on the ground), use some of the plywood from the curb form to protect the bag and rigid foam footing forms, and then order a couple of trucks of gravel from the stone slinger to bring the depth in the basement up to the required finished depth as this task will obviously not be possible once the floor assembly is in place.

I will then start framing the basement and getting the first floor assembly in place prior to starting the foundation waterproofing, insulation, and finally back-fill.

Hopefully in 6-8 weeks, I will be finally out of the hole!

Thanks for visiting.

 

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Pre-Pour Site Visit

April 22, 2015

For those interested, I did a pre-pour site visit video.  Sorry for sound and video quality.  Did not realize it was so windy and also that I was so shaky that day.  I will also post in next day or so a compilation of snap shots of the pour process.

Here is the pre-pour vid

You can also find this under the foundation channel of my YouTube library on this site.

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Relief!

April 21, 2015

Yesterday the foundations were poured and I am relieved on so many levels.

1) Last Oct/Nov – I would have never imagined that my back would have held out while I installed the 50-100 lb ICF blocks (depending on water content).  But with the help of Dr. Akhavan at the Vancouver Spinal Decompression Clinic, I made it through that task.  Funny, it was not the heavy lifting that got me in the end, it was the constant position of being prone bending slightly forward while I did the rebar and insulation, that has caused a major regression in my back recovery.

2) Even though I delayed the pour a week, I still only finished the required preparation at noon on Pour day (we were supposed to start at 12:30 PM).

3) On Friday, I had my District inspection but was told they still had concerns and would need to ‘talk’ about it on Monday AM.  This is despite me providing all of the engineering signs offs they had previously requested.  They have a very STRONG prejudice against the Durisol ICF and have made it clear they will not allow on another structure in North Van until the manufacture gets a full CCMC report for the product, or the applicant uses the ‘alternative method’ (something I have not researched but am told there is a cost for).  At 8:21 AM on the pour day, the District advised I could go ahead and pour (I believe they took pity on me).

4) I had concrete set up for arrival at 12:30.  At 10:30, I received a call form Kask (div of Lafarge) advising my placer had put a hold on the concrete because they were delayed at their morning job.  Unfortunately the pumper truck (Peter from F&F Concrete) was already on his way, so he ended up sitting around for 2 hours.  We finally got started at 2:30 PM.

5) The crew from High Def Concrete did a fantastic job.  Mat sent his very experienced father to do the placing and it went flawlessly. John was a pro and filled the blocks in a way that minimized the form pressures.  I had zero blowouts and because I used plasticizers for the 8″ slump, there was not even any bleed water visible on the outside of the blocks.  This will result in a very strong foundation.  I was so relieved when the first 4 ft were poured and knew that the blocks were going to make it.  I had a huge concern that the blocks could have been damaged in transit with the shunting of the trains, and the damage would only surface when pressure was applied to the cavities of the block.

6) My plywood form work for the top curb held!  I had zero blowouts but I did have some healthy deflection of the plywood.  In some cases it is over 3/4″. It made for a pretty stressful final lift as we quickly saw vibrating was out of the question and even rodding and light tapping was causing deflection of the plywood panels.

I should have used 3/4″ plywood, instead of 1/2″, for the inside face of the forms.  But I was trying to use product I could re-use as sheathing later in the build. Interestingly, the outside face of the forms, that is covered over by the Roxul insulation inserts, had zero deflection.

The inside deflection will not really matter.  The longest south wall does not have trusses attached to it and just needs blocking at 4′ centres.  I may have to scribe the blocking for a tight fit, but that is it.  The other walls that do have the trusses attached to, will just mean the truss rim board will need to conform a bit to a curve and again should not be a problem (worse case will require some light grinding).  As the basement walls will be held off 1/2″ from the ICF face, they too should generally not be effected.  So the end result was that I used a little bit more concrete. On the concrete volume, I had about 1.5 cu. meters left over which accounts for the extra metre I ordered and the extra .5 metre that the placer tacked on.  This means my actual takeoff was VERY accurate.

Note for those new to ordering concrete, it is recommended that an extra 1/2 meter is added to account for spillage and possible blowouts and such, and there is aprox 1/2″ meter that the pumper truck cannot actually pump out. SO you should always order 1 meter extra.

7) It was awesome weather for the pour.  Rain would have made everything some much more unpleasant for the crew.

8) I have awesome neighbours!  Bahman (my landlord) even came over with a large chocolate cake to share with the crew!  They were all thrilled.  We ended the pour with all participants enjoying a small shot of scotch each that I provided thanks to a gift from another neighbours’ brother who had recently visited from Scotland after the recent passing of their mother.

9) I am most thankful that the bank’s appraiser will be coming tomorrow so that I can get me first construction draw and first advancement of funds on the project.

 

You will not see much happening at the ‘hole’ (as my neighbour Ron calls it) over the next week. I now need to catch up on general life including, a massive amount of book keeping and tax preparation, badly needed vehicle maintenance, outstanding commitments to neighbours, and just some down time to recoup.  Next tasks will obviously be the stripping of the forms (no small task with an estimated 5000-6000 screws used in the forms and scaffold), and then the start of the basement bearing walls so we can get the floor trusses placed. I did help the stripping process by going over today and giving the top of the plywood forms a good walk to get a hairline crack between the plywood and concrete.  This separates the two and makes removal a lot easier.

The placers got a real kick out of the fact I had marked the centre line of all the anchor bolts and hung them in place with fishing line.  But now with the critical spacing needed by the new braced wall section of the code, this was a wise preparation.

The placers got a real kick out of the fact I had marked the centre line of all the anchor bolts and hung them in place with fishing line. But now with the critical spacing needed by the new braced wall section of the code, this was a wise preparation.

Something else that I 'prepped' was to attach the bend dowels for the garage suspended slab to the ICF vert bars at the right height.  This allowed them to just be 'swung out' once the pour was complete, but the concrete was still wet enough.  I checked all this morning and all were well secured.

Something else that I ‘prepped’ was to attach the bend dowels for the garage suspended slab to the ICF vert bars at the right height. This allowed them to just be ‘swung out’ once the pour was complete, but the concrete was still wet enough. I checked all this morning and all were well secured.

This multi tiered garage west wall was a bit hairy.  We needed to let the concrete set up enough so that we could pour the top curb and not have it spill out the bottom layer.  I was advised I should have installed a boiler plate here, but there really was not room as the plywood was resting against the rebar.

This multi tiered garage west wall was a bit hairy. We needed to let the concrete set up enough so that we could pour the top curb and not have it spill out the bottom layer. I was advised I should have installed a boiler plate here, but there really was not room as the plywood was resting against the rebar.

Use of plasticizers means no bleed water on the forms and no cleanup.

Use of plasticizers means no bleed water on the forms and no cleanup.

I should have used 3/4" plywood for forming inboard panel of top curb.  This photo  shows some of the bowing that occurred.

I should have used 3/4″ plywood for forming inboard panel of top curb. This photo shows some of the bowing that occurred.

The outboard panels protected by the Roxul inserts had no bowing whatsoever.

The outboard panels protected by the Roxul inserts had no bowing whatsoever.

At the very end of the pour, I hand bucketed about half a yard of concrete to the very back of the property to finish off the footing for a fence I started 2 years ago.

At the very end of the pour, I hand bucketed about half a yard of concrete to the very back of the property to finish off the footing for a fence I started 2 years ago.

Thanks for visiting.

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Where’s the concrete?

April 16, 2015

I have had a few people today ask “what happened to the concrete?”  as today was my scheduled pour day.

Well – what else – there was a delay 🙂

Last Sunday I knew I was not going to be ready for today and postponed till this coming Monday and now I am happy on two fronts that I did so. First, I will need tomorrow and all weekend to finish preparing for the pour.

I finished the 10M continuous bar through the upper curb last Saturday and then started working on the insulation inserts that are being placed inside the form work.  The inserts were complete Tuesday.  I am using the insulation as ‘form work’ to save money, time, and materials.  It did not make a lot of sense to cut sheets of plywood up into small strips to create the block outs needed for the insulation that will eventually be installed anyway.  Why not just use the insulation to create the voids needed for the concrete.  At 745 psf compression strength, it should be able to handle the 3ft of concrete that will be stacked next to it (600 psf is enough to support 4ft lifts of concrete). I wrapped the insulation in poly to allow me to peel off the insulation once the foundation is poured to allow me to re-use the insulation and to allow for the waterproofing of the foundation.

Yesterday, Eric and Bert came by and helped check off numerous items on my action list including marking location of all anchor bolts and then hanging a bolt from fishing line at each location so easily placed during pour.  They also wrapped the threads with tape to prevent fouling by the concrete. Bert also did a major cleanup of the site, moving a lot of material I had stored along the property line, down into the pit near the eventual basement walkout.  This way it is out of site of the neighbours.

While they were occupied, I was working on the vertical supports for the top curb and continued this task today.  I hope to finish the form supports tomorrow and then work on the multiple foundation penetrations for the plumbing, HVAC, and electrical over the weekend.

The second reason it turned into a good decision to delay relates to the fact that I have yet to have my District inspection.  On Monday, my inspector emailed stating he was sick and would not be able to do my inspection.  The file was given to another inspector but they called and advised they could not do the inspection because of ‘issues’ with the file.  I advised “no problem, as long as Richard can do by today, I will be fine”.  As of this morning there was no follow up and when I phoned, I was informed Richard was still off sick and that I had to speak with the Building Manager.  I went down in the afternoon and it turns out that the Manager was not aware that I had received sign-off, by a building envelope engineer, for the foundation waterproofing.  It was clear the Manager had a strong prejudice against the Durisol ICF.  I presented all of the various schedules that had been requested of me, and this seemed to do the trick.  I have booked another inspector for tomorrow – so here’s crossing my fingers (and toes).

Monday will either be a great day or a disaster – I am on pins and needles to find out which!

Thanks for visiting.

 

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On the Level!

April 10, 2015

It has been a great couple of days.

I have now received the sign-off on the structural inspection of the forms.  I had given Tacoma a heads up that Brian from Stantec was coming and needed a fast turn around.  Well within 45 minutes of getting Brian’s site report, I had Tacoma’s in hand as did the District inspector.  Tacoma have been awesome in this process and very attentive to my time sensitive questions as we proceed through the final stages of the foundation forming.  I continue to be convinced that they were an excellent selection as part of my ‘team’.

I also received the official survey yesterday and the actual data points today.  Would you believe that there is less than a 1/8″ variance between the elevations of all the corners of the foundation (and of course the elevation is the elevation we were going for).  I am very pleased with this and it shows that both the laser level and its operator are VERY accurate.  All of my corners were also less than 1º out from a perfect 90º .  My wife told me that my father would be proud if he was still with us.  He was a Master Carpenter throughout his life (long before I came on the scene), and I guess I must of picked up some of his genes as he was long retired when we met for the first time, so it was not a direct transfer of knowledge.

I have the District inspection set up for Monday and look forward to going through the forms with Richard who I am sure is relieved now that I have also provided to him the sign-offs from the Building Envelope engineer for the waterproofing (something that his boss demanded).

Today we also got the awesome news that our construction mortgage has been approved.  We were approved last March but because it had been so long, and we had not done a draw yet, we had to start the process over and now we have a considerable amount more debt.  We have over $180K into the build to date with $50K coming out of cash-flow over the last year and the rest coming from various LOC’s I have been able to secure. So as long as next Thursday’s pour happens, we should be able to get a significant amount of money before the end of the month (when taxes are due), and I will for the first time during this project, not be stressed about how we are to pay the next visa with all of the construction materials on it.

Today I finished the 10M bar around the top curb and installed the last beam pocket. Yesterday I did some of the other beam pockets and also fixed the forming on the North wall.  If you look at my S12 drawing, you will see I have three different profiles for the top curb of the north wall.  Somehow this fact escaped me while I was forming that wall and I formed it up just like the rest of the house.  Fortunately I caught it and after a couple of hours all was good again.

Even though I am basically ‘done’ with the forming, I still have a very lengthy list of items that needs to be done before the pour, so I am very happy that I delayed till next Thursday.

Thanks for visiting.

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Thank full for friends

April 8, 2015

It has been a reasonably productive few days.  On Friday Ted was by and we were able to install the crucial vertical uprights, on the outboard side of the foundation, needed to install all the whalers at the top of the formed curb that will sit on top of the last row of ICF.

One of the functions of the formed upper curb was to create a bump-out flush with the top of the floor trusses to provide an extra 2" of floor space and ensure that the drywall lined up with the framed wall above.

One of the functions of the formed upper curb was to create a bump-out flush with the top of the floor trusses to provide an extra 2″ of floor space and ensure that the drywall lined up with the framed wall above.

Over the holiday weekend, I was able to quietly install all of the plywood making up the inboard side of the formed curb, frame up the special form needed between the house and the garage (needed half the thickness of the foundation at finished height to allow the attachment of the floor trusses, but needed the other half to create a much lower shelf that the later poured garage slab will sit on), and start installing the 10M bar that is to run continuous through the top curb.

I used a 1.5" chair to ensure the continous 10M bar running through the top curb had the required 1.5" inside cover.  I just drilled two holes in the plywood and used tie wire to secure so that it also had 1.5" top cover.  A fast and easy installation.

I used a 1.5″ chair to ensure the continuous 10M bar running through the top curb had the required 1.5″ inside cover. I just drilled two holes in the plywood and used tie wire to secure so that it also had 1.5″ top cover. A fast and easy installation.

At any interuptions to the 10M horizontal bar (like around door openings), the bar has to be bent outboard so that it is in the centre of the curb, and then travel vertically down 18" to develop an 'equivalent' continuous length. The vertical portion need 2" cover between it and the blocked out opening.

At any interuptions to the 10M horizontal bar (like around door openings), the bar has to be bent outboard so that it is in the centre of the curb, and then travel vertically down 18″ to develop an ‘equivalent’ continuous length. The vertical portion need 2″ cover between it and the blocked out opening.

Yesterday I arranged the structural inspection of the form work with Brian from the Victoria Stantec office, as he was going to be on the Mainland for other appointments.  I have not seen his report yet, but he seemed satisfied with the placement of all the rebar.  His report will go to Tacoma who will then issue the official Site Report I need to provide to the District inspector at the beginning of his visit.  I also had the foundation forms inspection completed.  They were a very happy crew as the scaffold made their job fast and easy.  I do not have their documents yet, but when I inquired, they downloaded one of the elevation checks and I was only 1/8″ out from where I wanted to be.  I was quite satisfied with that.

Today my father-in-law and his friend Bert came and we checked off a number of outstanding items on my list. While Eric was de-nailing the final 60 or so salvaged 2×4’s, Bert was able to totally clean up the pit and around the site.  He stacked the rebar I had ordered that was too short for later use in the basement walkout, cleaned up all the debris around my various cutting stations, and collected all of the broken and cut bits of ICF and transferred all to the trailer for a later trip to the dump.

While they were occupied I constructed 2 boxes to create the pockets needed for 2 of the beams that will sit on the foundation walls. Earlier this morning while drawing up my details for the day (I sketch up everything in AutoCAD so that I have accurate dims to go by and to look for issues before actually starting to build), I discovered a major snafu with one of the beam pockets – it had 2x 20M bars running through it that were needed to strengthen the wall beside the basement stairs.  A series of emails to the engineer solved the problem by changing the design to support the beam on a 3-Ply 2×4 post that will just sit on the floor slab (it was a fairly lightly loaded beam).  I have asked Tacoma to also look at another dropped beam pocket because it is on the corner of a wall and will penetrate into the ICF layer, and at this point with the upper curb formed, will be difficult to cut in (I should have had the beam pockets higher up on the action list).

Beam pockets are easy to fabricate with some plywood and 2x4's

Beam pockets are easy to fabricate with some plywood and 2×4’s

Completed pocket installed into form work.

Completed pocket installed into form work.

After lunch Eric, Bert and I all worked to fabricate another 15 or so uprights and finished the day with filling in all the gaps between the uprights that Ted and I had installed last Friday. This will leave me with only inboard uprights to install which I can do by myself from the scaffold.

All the vertical supports are now placed on the outside of the wall.  I still have to properly anchor them with better screws and then also attach a 2x2 horizontally along the bottom edge of the plywood to clamp it to the ICF blocks securely and prevent blowout.

All the vertical supports are now placed on the outside of the wall. I still have to properly anchor them with better screws and then also attach a 2×2 horizontally along the bottom edge of the plywood to clamp it to the ICF blocks securely and prevent blowout.

I am thank full to have friends that help take care of some of these tasks that would be more difficult to do by myself!

Even with this progress, I suspected I was not going to be done for Monday, especially since my back has suddenly got much worse again, and have therefore re-scheduled the pour for Thursday the 16th.  I received confirmation from both the placers and the pumper that this day works for everyone.  This way I can take the time to make sure the forms are complete and well supported, so that we do not have any surprises on the day of the pour.

Thanks for visiting.

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Foundation Rebar Primer

April 5, 2015

I received some feedback to my journal posting yesterday that was suggesting I should look at the ‘other’ ICF manufacturers if I wanted to know how Rebar was ‘supposed’ to be placed.  I did and the result sure is scary.  Because you are allowed to install ICF walls without ANY engineering assistance (as long as you meet the building codes requirements including max unsupported wall height) and therefore engineering inspection, there is a plethora of miss-information out there regarding the requirements for rebar reinforcing of an ICF wall.

At least the BC Building code makes it pretty clear on the requirements, but I suspect that because the Municipal inspector is not present at time of pour, these requirements may not be adhered to – at least that is what is evidenced by one of the discussion forums I visited last night.

So – lets first look at the BC Building Code requirements.

The Horizontal rods are to be installed every 2 ft vertically and are to have 1-3/16″ inside minimum cover (30mm) meaning that the rod is to be held off the outboard surface of the inside ICF panel to allow 1-3/16″ of concrete to be present on the inside face of the bar.

The Vertical rods are to be installed per tables BCBC 9.15.4.5 A to C depending on core thickness and height of wall.  The first options calls for vertical rod placed every 16″ horizontally with again 1-3/16″ inside cover (30mm) minimum.

Obviously both vertical and horizontal bars are unable to occupy the same plane off the inside face of the foundation, so the code also specifies a max cover by stating the bars are to be “located located in the inside half of the wall section”.

My requirements were much more stringent because of the height of the wall.  The engineer specified vertical bars every 12″ horizontally and horizontal bars every 2′ vertically.  I was not given a range for the vertical bar – it required 1.5″ of inside cover.  When I asked if 2″ or even 2.5″ would be OK, I was informed that they would have to rerun all of the calculations and that they suspected there would be problems.  So, I did by best to ensure 1.5″ cover.

My drawings also specified 1.5″ cover for the horizontal bars, but I failed to abide by that when placing the bars.  Because I drew up the structural drawings (with the instructions received from the engineer), and had drawn the horizontal in the centre of the core, and because I am more of a visual person instead of word person – I placed the horizontal bar down the middle of the blocks during installation.  Fortunately, my blunder was forgiven.  When doing the calculations for the wall, the engineer had generally only used the vertical bars in the strength calculations and the horizontal bars were more present for crack control. I was very relieved (and thank-full to Tacoma for providing very fast responses to all of my rebar questions), as by the time I had discovered the blunder, all of the horizontal bar had already been placed.  While waiting for the reply to come the following morning, I tossed and turned all night worrying I was going to have to disassemble the wall or pay for a fibre additive to add to the concrete for strength, like the Helix fibre (you may remember from an earlier posting, I was looking at this but had ruled it out as being too costly considering it could not replace ALL of the vertical rods).

The most important point of this primer is that you MUST pay attention to the cover stated for each bar installation.  A bar placed without the appropriate cover almost becomes a bar that no longer contributes to the strength of the wall. For instance, if the bar was placed on the outside half of the core, you may as well not even have it there.  This brings me to the next part of my primer.

Rebar chair is used to hold rod at a precise cover off the inside face of the forms

Rebar chair is used to hold rod at a precise cover off the inside face of the forms

Why is rebar installed in concrete anyway?

Concrete has awesome compression strength but is quite poor in tension. Because the weight of the back-filled soil is pressing on the foundation, it wants to  ‘bow’ inward under the pressure.  This would place the outside half of the core into compression but would place the inside half under tension (just like a floor joist but in a vertical plane).  The inside half of the concrete core is trying to stretch to accommodate the bow.  As concrete is not good when pulled on, the stretching would eventually cause the concrete to fracture.  By placing rebar into the concrete, it prevents the concrete from stretching too far and fracturing.  The closer the bar is to the inside face of the concrete core, the more tension forces it will encounter.  Another way to look at this is the distance it would take to run or drive around the outside of a track compared to the inside lane of a track.  The further outboard you get, the farther you run or the longer the circuit is.

So, if your wall is designed with 1.5″ inside cover, that means the engineer has calculated the stresses of the wall at that 1.5″ plane and ensured to call out a rebar pattern that can accommodate those stresses. If there is not enough cover, then there will not be enough concrete to properly capture the bar and keep it in place, but if there is too much cover the rebar will not be able to remove enough of the load from the ‘stretch’ of teh wall and the concrete will fracture. If the rebar was placed in the outside half of the core, it would no longer be subjected to ANY tension and in fact would be being squeezed by the surrounding concrete that is under compression forces.

While researching this last night if came across the installation instructions for a very popular rigid foam based ICF (and the manufacturer that was reportedly sued in the West Vancouver failure).  They instruct the installer to “Place plastic sleeves (1½” [38mm] conduit) over stub steel for later placement of vertical steel” meaning to slip chunks of plastic conduit over the dowels placed in the footing to later capture the bottom end of the vertical rod.  But as the dowels are placed typically down the centre of the footing, this would place the vertical rods down the neutral plane of the foundation wall, or a spot it will do very little good to resist the tensions of the foundation wall.

I also came across this forum on greenbuildingtalk.com discussing the placement of the steel and it was very clear a majority of the contributors did not truly ‘get it’. Lets quickly correct some of the miss-information.

  • Why do we tie off rebar under some circumstances?

Simply to hold the bar in the RIGHT position until the concrete has been poured and can hold the bar for us.  It provides NO structural strength whatsoever.

So why is the tying off of the rebar inspected before pouring by the engineers? Why is it important that the tie-off securely fastens the bars together?  Because as we have discussed above, it is critical that the bar is placed in the right position to ensure it can bare the intended load.  As the tie wire is quite brittle, if the bars can move slightly because of not being tied-off tightly, there is a chance the sudden shock of the movement could break the wire which would now allow for the bar to move substantially out of position.

  • Is it important that the horizontal bars are tied to the vertical bars (something that cannot be done in ICF construction)?

No – full stop.  Each orientation of the bar is typically handling separately calculated loads and not considered an ‘assembly’ (In some extreme cases I do believe it is a ‘grid’ that is designed, but in these cases sophisticated FEA software is used and the bar must be welded together not tied).

  • Is staggering the horizontal bars to capture the vertical bar the required solution?

No – this is only appropriate for above grade ICF installations.  In order to ensure the vertical bar was placed inboard enough on the core, the inside horizontal bar would not have enough cover.

  • Why is it important to tie-off splices?

You need to ensure that the bars are fully encased in concrete.  If the bars were not tied tight to each other, they would allow small pockets to form between the bars that were too small for the flow of concrete.  This would provide a weak point because the bar would now not be in communication with the concrete and therefore unable to bare the intended load.  This is why bars in close proximity, and in the same plane, need to be tightly bundled or held apart a minimum distance by means of chairs or other securing.

  • Why do the vertical bars not need to be tied-off or otherwise captured to the footing dowels?

Footing dowels or any other dowels have nothing to do with the tension stresses a concrete  assembly is under.  Their sole purpose is to tie the concrete on each side of a cold seam (concrete poured at two different occasions) together.  SO in the case of a footing dowel, the purpose is to ensure the foundation wall cannot ‘slip off (shear)’ off the footing.  This is why most codes also allow the formation of a key in the footing, instead of the dowels, to capture the bottom side of the foundation.

Hope this has been of some assistance. Should there be something that you disagree with, then please provide documented background for your disagreement and I will reconsider.

Thanks for visiting.

 

 

 

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Final Foundation Push

April 4, 2015

Sorry for the silence folks, I have been on the final push to finish off the foundation forming.  I have my structural inspection, and also my survey, scheduled for Tuesday the 7th, and will try to schedule the District’s inspection for the 9th or 10th latest. If all goes per plan, we will pour the foundations on Monday April 13th!

Over the last 10 days I have finished placing all of the rebar (vertical rebar secured to top row of horizontal rebar, rebar for the lintel over the basement walkout door, 2x 20M bars that will strengthen the foundation beside the basement stairs up to the first floor) and also started forming the top curb that sits around the perimeter on top of the ICF.

I had a setback on the rebar, made a mistake on a dimension and ordered about 100 bars a foot too short, but worked through it (reordered) and will be able to use the shorter bars for much of the basement walkout stairs and retaining wall.

Placing the vertical rebar is a real challenge in ALL ICF construction (regardless of manufacture).  There is no way to ensure the bottom end has the proper concrete cover and will stay in place during the pour.  I was more fortunate than most because I poured my first row of ICF with the footings, did not fill that row to the top, and did not smooth out the concrete inside the bays of that first row.  This generally allowed me to find an appropriate divot in the first pour to ‘anchor’ the end of the vertical bar into.  I would then give a good smack with the hand sledge to seat the bar in the divot and then tie off the top of the vert bar to the horizontal.  If I did not find a suitable crevasse to anchor the bar into, I sharpened one end of the bar with a grinder and then pounded that end into the concrete to secure.  I cannot guarantee it will work, but it will be better than most other ICF jobs I am sure.  If I was to do this again I would look at placing an extra 10M horizontal rod at the first row, just off the inside face of the ICF, to sandwich the vertical between the 10M and the regular 15M horizontal bars (placing the horizontal bars to ensure the vert had 1.5″ cover).  Or I would look at putting in rebar caps upside down into the wet footing concrete to capture the vert bar when lowered later from the top.  The vert bar is a problem with ICF installations (below grade), and I am aware of a recent $1M lawsuit in West Vancouver against the ICF manufacturer and engineer of an ICF foundation where the bar was not properly captured by the forming process and on investigation some of the bar was even able to be pulled right out of the foundation without the use of tools.

Over the next couple of days I hope to finish the form work and hang the final 10M bar that is to run continuous in the top formed curb.  Next week I will have to install the block outs for the first floor doors and the basement beams, and also install the various electrical, plumbing, and vent pipes that will be penetrating the foundation.  I will also need to brace all of the cut joints in the ICF, install the remaining uprights to secure the wall, and finally install all of the diagonal bracing to secure and plumb the wall prior to pour.  It will be a very busy week!

Variable height of bars caused by variable fill height of first pour in the first row of ICF.  I will probably need to trim some of the longer pieces so that they have the appropriate top cover.

Variable height of vert bars caused by variable fill height of first pour in the first row of ICF. I will probably need to trim some of the longer pieces so that they have the appropriate top cover.

Lintel over door for conditioned basement into cold room under garage.

Lintel over door for conditioned basement into cold room under garage.

Lintel created with bottom 15M bar and 10M stirups

Lintel created with bottom 15M bar and 10M stirrups. Top bar is just present to hold stirrups

Lintel on basement walkout created with two 15M bars bundled.

Lintel on basement walkout created with two 15M bars bundled. Still need to adjust to ensure 1.5″ inside cover. Notice also the Roxul thermal break installed between the concrete and the later installed door frame.

A bundle of bars - each side of an opening or end of an ICF wall needed two extra 15M vertical bars installed.

A bundle of bars – each side of an opening or end of an ICF wall needed two extra 15M vertical bars installed.

Because the stairs from the basement to the main floor runs along the side of the foundation, this means that the foundation in this region is not laterally supported at the top (it does not have any tie in to the floor diaphragm).  As a result the engineer specified two 20M bars installed 6" apart with 1.5" inside cover and starting 16" below the top surface of the floor assembly.

Because the stairs from the basement to the main floor runs along the side of the foundation, this means that the foundation in this region is not laterally supported at the top (it does not have any tie in to the floor diaphragm). As a result the engineer specified two 20M bars installed 6″ apart with 1.5″ inside cover and starting 16″ below the top surface of the floor assembly.  As these ICF blocks have been significantly weakened by the cut out required, extra bracing in this area will be needed.

As part of the extra strengthing needed due to the stairs, 24" on each side of the stairs has the vertical bar spacing reduced from 12" to 8" max O.C.

As part of the extra strengthening needed due to the stairs, 24″ on each side of the stairs has the vertical bar spacing reduced from 12″ to 8″ max O.C.

One of my favourite quotes of late (and most relevant):

“I am only one, but I am one. I cannot do everything, but I can do something. And I will not let what I cannot do interfere with what I can do.” —Edward Everett Hale (1822-1909) American Author

Thanks For Visiting.

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