Building my own ICF (6" Logix) house, 1700 sq.ft. bungalow on a 4 ft icf crawlspace in Frosty Manitoba. Have the 4 ft ICF grade beam poured on top of a shallow footing, installing the floor this week and starting on the main walls this weekend. Most local contractors use 3/4" PT plywood with a 2x4 or 2x6 ripped on a 45 deg angle. I don't understand the logic of doing this. Can someone explain the intention of how this works. I know someone who is willing to give me a hand to get started with the PT bucks, but I was thinking of trying the Insulbuck. Has anyone used this with repeated success? Thanks for your time, Greg.

Greg - there are several threads on bucks. One thing you will find is those that use p.t. will always defend them. There are a few advantages but not enough to offset the problems. By using 45º cuts the lumber is locked to the concrete (the widest portion is away from the plywood.)

The other thing you will will find is that wood always moves! If you use wood bucks make sure you wrap them. Hot wet concrete will swell them and it takes about two years for all the moisture to come out. At that time there will be cracks between the concrete and the bucks which you can't seal because (hopefully) the house will be done.

Any foam buck is much better in my opinion. You will totally encapsulate the concrete at the openings. Make sure the buck matches the block. I'm not sure Logix makes foam bucks but the Insul buck might fit. If not just use scrap pieces to fit between the foam panels.

Use a block that has proper dovetails in the inside of the block and a matching buck makes live much simpler. We have used Nudra and Integraspec for the last decade or so and would never go back to wood bucks. I strongly believe that the concrete core should only touch foam. This is what makes the thermal mass of the ICF work so well. In my own house just outside Calgary the ICF performs better than R50.

FBBP, interesting on the foam. I assume you would use a 2x10, plywood etc with bracing to support the foam while pouring and then screw in a vinyl or metal flashing, in order to install the windows/doors?

I used PT dimensional lumber for the bucks and I don't have cracks.

Greg
For a window opening, if the foam panels are dove tailed the bucks stay in the sides with out the need for bracing.
We generally place panel cutoffs in the sill and use a hole saw to cut out a couple holes to pump into.
The same is done for the header without the holes. A piece of form ply is laid in each sill corner to allow an upright brace to hold up a header brace that is usually a piece of ply with two 2x4's on edge. They are 3.5" apart to allow the upright brace to fit between. If the window opening is larger, you will need intermediate supports as well. If needed 1x6 boards or sheathing scraps are screwed into the header ply and into the web of the block above the header.

If we are placing windows with flanges, we screw the upper and lower flanges into available webs to level and secure. Then the rough opening is filled with adhesive foam.

If adhesive foam is used the window can only be removed by cutting the foam.

Flashings are not needed to install the window but might be needed depending on your exterior cladding.

The foam and concrete are all dimensionally stable regardless of moisture content so once the assembly is complete, it stays complete.

Posted By FBBP on 01 Oct 2013 02:07 PM

Use a block that has proper dovetails in the inside of the block and a matching buck makes live much simpler. We have used Nudra and Integraspec for the last decade or so and would never go back to wood bucks. I strongly believe that the concrete core should only touch foam. This is what makes the thermal mass of the ICF work so well. In my own house just outside Calgary the ICF performs better than R50.

I agree, I also believe it is a far better method and result when the window and door bucks avoid the use of wood, even pressure treated. As the saying goes, "Why wood you?"

People have and still continue to use pressure treated lumber and most are probably still doing fine. Although I would like to see a study or a tear down of an ICF window buck area that had PT wood after 10+ years of service. I would be curious to see how "tight" the window area is and if any significant gaps have occurred from the wood drying and moving around.

Wood bucks are easier/faster, less expensive, and readily available. Those are their main selling points.

Video of foam buck

Quote,
"Wood bucks are easier/faster, less expensive, and readily available. Those are their main selling points. "

I guess I disagree LBerar, Maybe utilising wood bucks is a form of loving your neighbour, for instance the tradespersons who follow your work. How about attachments for the drywaller, the trim guy, the siding installer, the window treatment trades- which a continuos wood buck provides.

Ladies and gentlemen, its not all about selling your foam!

Stop by my shop. 10 years in 20% humidity. No cracks no gaps no problems.

I think its time to provide structures people need, not what salesmen want to sell. Its time to quit jacking up the price of ICF structures with needless bells and whistles.

Yahoo for wood and plastic and foam and concrete and steel all working together.

Posted By irnivek on 04 Oct 2013 12:12 AM
Quote,
"Wood bucks are easier/faster, less expensive, and readily available. Those are their main selling points. "

I guess I disagree LBerar, Maybe utilising wood bucks is a form of loving your neighbour, for instance the tradespersons who follow your work. How about attachments for the drywaller, the trim guy, the siding installer, the window treatment trades- which a continuos wood buck provides.

Ladies and gentlemen, its not all about selling your foam!

ICF's use the plastic attachment strips for installing siding, drywall, window treatments, etc. How does throwing in a 2x4 wood buck around some windows somehow negate that 95% of the ICF home uses plastic attachment strips everywhere. The 5% of wood around a window doesn't make it better for any of the attachments. One can easily install any of those items mentioned directly into the foam buck.

BTW - I don't sell any foam or ICF.

It's about making the structure better by using new technologies. Some people don't want wood in their ICF structure. If they were a fan of wood they would have just built a wood framed home.

Using PT wood around bucks is not a bad thing to do but like FBBP mentioned, and as others have, there are better alternatives and give you a 100% ICF structure.

Let's compare some figures, materials cost only, wood will cost you roughly $ 1.00 per ft. for argument sake, give or take a nickel, these new bucks being introduced on the market are running at $ 5.00 per ft plus.

We are currently on a project with over 1500 l/f of window/door buck requirements, so the math is simple, material cost alone are an additional $ 6000.00 on this one project.

Properly installed wood bucks normally have no issues, yes, wood can check and twist, but in general no serious issues, proper flashing seals them, so any movement will not create air problems. And at the end of the day...that up charge is not a quick payback on your energy costs. ICF maybe a few % points more, compared to conventional builds, but the energy payback alone and timeframe justifies the additional costs today.

I feel these buck companies are creating a solution for problem that really doesn't exist.

You guys realize in commercial we remove the bucks and fasten the windows directly to the concrete? The same could be done in residential...only most residential window installers do not have the knowledge or experience in fastening directly to concrete.

When I read the different forums on gbt I'm amazed at the detail people building stick frame go to to seal their window openings but I am just baffled by people who chose to build with ICF because they know it is the best building envelope for the buck but then take such a cavalier attitude to the one place where you will get infiltration on an ICF envelope.

I'm not suggesting that the fancy bucks are the way to go but people who have not chosen an ICF supplier with proper bucks may have no choice.

Mounting to concrete. That means the the window jamb only has the benefit of one layer (the outside one) of ICF for thermal protection. If you are using commercial aluminum storefront, it would mean that the aluminum would likely be the first condensate point in the building, possibly even lower then the glazing itself. Yes you can double space the opening, roll in some backer rod, foam and caulk the thing but why would you not just put in the foam inserts and have it done with? If using wood windows and there is even a little leakage, the vapours will condense as soon as the hit the concrete core and the next thing you know the window jamb is rotting. And of course the will blame the stucco! Using Nudura's bucks is much quicker then wood for the sides so the math would be in their favour.

Wood and concrete (or most lime based products) make for a lousy marriage. The concrete is content enough but the wood keeps trying for a separation!

Posted By Chris Johnson on 04 Oct 2013 04:23 PM

Properly installed wood bucks normally have no issues, yes, wood can check and twist, but in general no serious issues, proper flashing seals them, so any movement will not create air problems. And at the end of the day...that up charge is not a quick payback on your energy costs. ICF maybe a few % points more, compared to conventional builds, but the energy payback alone and timeframe justifies the additional costs today.

I feel these buck companies are creating a solution for problem that really doesn't exist.

I think you are missing the point here. I am not saying the PT wood bucks are the worst thing in the world. What I am saying is that with building science, we are always advancing and trying to improve on the building envelope. Making the home stronger, more energy efficient. As with technology, we keep trying to improve.

When case studies were done on ICF homes and their thermal values along with their air leakage values were scrutinized. One factor always stood out in all the studies; the weak point of an ICF home are the window and doors openings. Not the windows themselves (triple pane vs double pane). It was the thermal bridging around the doors and windows and the air leakage around doors and windows that was a weak point in the ICF homes.

ICF homes boast that they are tight, which the walls are. All of that is meaningless if the windows and doors areas leak air and energy escapes from those areas.

The buck is not to blame for this, improper installation is the key factor to all these serious heat loss issues. We try and educate consumers on ICF walls, but fall short on proper installation and sealing of windows, doors, service penetrations, roof connections.

Even with these 'Green' window bucks, an improperly installed opening which includes proper flashing and sealing is going to create the same effects and issues as wood. Properly installed wood bucks will remain in place for a long time, longer then me.

Posted By Chris Johnson on 05 Oct 2013 12:03 AM

Even with these 'Green' window bucks, an improperly installed opening which includes proper flashing and sealing is going to create the same effects and issues as wood. Properly installed wood bucks will remain in place for a long time, longer then me.

I agree, anything improperly installed will lead to problems. Dimensional lumber quality seems to be deteriorating and there was a Building Science article on it not too long ago. Green treated lumber always splits and distorts. Lumber that is soaked in that stuff, when it dries over the next 2-3 years, will not remain true. If it is forced to do so (via anchor bolts and window frames), can it exert pressure on those things and cause problems?

I want to dispel some misconceptions about pressure treated/green lumber:

• Pressure treated lumber DOES rot and will rot when exposed to moisture
  
• Termites will bore & even consume treated lumber. It is not termite proof

With that being said, in termite country, why open the door to having problems by installing PT wood window and door bucks?

How do you thermally break the 2x10 or 2x12 wood and door buck?
Do you install a capillary break between the buck and concrete and if so, how soon after the pour?

Treated lumber can warp when it is against curing concrete, but if everything else is in place, it will dry true. Mine did. Every piece.

It was the thermal bridging around the doors and windows and the air leakage around doors and windows that was a weak point in the ICF homes.

Lbear,; it's like everything else. There is give and take unless you are trying to build the most spectacular passive home in existence. Everything has to pass the value for cost test and barking at PT bucks is way down on the list.

Posted By ICFHybrid on 06 Oct 2013 10:35 PM
Treated lumber can warp when it is against curing concrete, but if everything else is in place, it will dry true. Mine did. Every piece.

ICFHybrid,

It takes 2-3 years for PT lumber to fully dry out. Once it is encased in the finished wall, how does one know if it remained true and intact?

This is from a PT website:

• After being outdoors for 6 to 12 months, treated lumber will develop cracks, called "checks," along the surface of each board. These hairline cracks are a normal part of the drying process.

Pay close attention to the "outdoor" part as PT lumber encased within a wall will take double the drying time of outdoor PT exposed lumber. 

Lbear,; it's like everything else. There is give and take unless you are trying to build the most spectacular passive home in existence. Everything has to pass the value for cost test and barking at PT bucks is way down on the list.

The Achilles heel of ICF is always in the wood and door areas, followed by the roof and top plate detailing. Poor detailing in the wood and door areas, even with vinyl/EPS bucks will result in air/water leakage. The PT lumber when installed might look all straight and true but once the windows are installed and drywall is installed, one cannot know what is going on with the PT lumber when it is hidden behind the wall.

My point is that PT Lumber will check (develop cracks) and it will move around within the window and door area over the span of install to 2 or 3 years later. These are all potential leaking points for air and water. I would rather build a window frame area out of NON-PT wood than use PT wood, at least the NON-PT wood is more dimensionally stable.

One also has to remember with ICF walls that PT wood and door bucks was the result of not having any alternatives (besides steel bucks which are are horrible thermal bridges). Later on different manufacturers began to come up with better alternatives like V-bucks, Gorilla bucks, etc. The cost was higher than PT wood but as with most new products, over time the costs began to drop a little with competition.

Companies like Fox Blocks wouldn't have spent the time and money to engineer a new window and door buck if they didn't believe the market had a need for it. The prices will come down over time.

Between PT-wood and non PT-wood, I believe the non PT-wood is a better alternative but the cost is more and one has to be careful with moisture mitigation. The advantage is that non PT-wood is a lot more dimensionally stable.

Here is a good read:

ICF MAG - Bucks


From a DIY website:

I built a new very large deck out of the latest treated wood. In 1 year the boards had warped enough to pull through the screws and the shrinkage was amazing. I had 1" gaps between the ends of boards. The sides were installed with no gap and they had 3/4" in 10 months. We ended up tearing off all of the 1 yr old boards and installed the new composite boards. ( awesome ) The sub frame of the deck had to be straightened with jacks and re- bolted and secured to be level. Some of the 2x10's under the deck were replaced because they looked like rocking chair rockers.


The above describes exactly what PT-wood does over a course of a year while drying outdoors. I am confident that PT-wood when examined in an ICF window area 2-3 years after initial install will NOT be true and sealed. It will have cracks, splits and will have pulled away in areas, exposing gaps. I would not be surprised to see window frames being stressed because the PT-wood warped and began to exert pressure on the window frame.

It takes 2-3 years for PT lumber to fully dry out. Once it is encased in the finished wall, how does one know if it remained true and intact?

Really? Well, mine dried faster than that, but before we put siding on and finished the interior so we could inspect the results. From both sides.

Dry. Straight. True. No cracks. I also wouldn't consider the exposure to be the same as that of wood "outdoors" as there is no UV, no rain and considerably less temperature variation.

We don't use PT here for our bucks, that's an American thing I use to have to do, Canadian code allows for regular SPF in contact with concrete as long as we are 6" above grade, every window and door is 6" above grade.

Barring that, I also use blueskin, 6" rolls, wrap the outer edge of the buck to the ICF, should that buck decide to move, the peel and stick is still sealing any air infiltration, after the window is install and additional layer of blueskin is installed over the nailing flange and onto the face of ICF. Seems pretty well sealed to me.

LBear, the majority of the splits and checks are minimal, yes, twisting and warping can occur, again normally a minor amount, and usually only during the extended exposed process between the build and roof on, windows installed. If this time frame is quick, not much twisting, if it's a few months where moisture comes and goes (rain) I have seen problems.

I know you base a lot of your information on research here and there, but sometimes, us guys who do this daily in the real world, know how to account for what your reading and make adjustments for it.

Posted By Chris Johnson on 07 Oct 2013 10:27 PM
We don't use PT here for our bucks, that's an American thing I use to have to do, Canadian code allows for regular SPF in contact with concrete as long as we are 6" above grade, every window and door is 6" above grade.

I think that is what makes a night and day difference. PT wood is like a Yugo while untreated lumber is like an Audi when it comes to wood window and door bucks. PT lumber is pretty nasty stuff.

I agree with you 100% that untreated lumber with a capillary break is a solid window and door buck. Canada tends to be more rationale with their codes. Here in some states and counties they force the PT lumber on you.

One thing about Canada though is that you guys don't have to deal with termites like we do here in the south.

On a different note, did you use those Schock thermal breaks on that high rise project?

No, I use untreated lumber with concrete cast directly against it...and leave it there, I seal from approx. 1.5" on the exposed face of wood buck, across the edge and onto the ICF. I wouldn't call Canada more rational with their codes either, I'd say equally different. Having built in California and Ontario, the best way I can describe it is, some of their codes, some of our codes all combined we would have the perfect code book.

And yes, we have termites, google East York Ontario termites, and they are spreading. We are currently doing 2 projects in the area, one of them had the ground sprayed after excavation, before footings and will be sprayed again after foundation gravel but prior to slab placement.

Schock product pricing scares people off, I am in talks with another project that could benefit from it, however, based on a previous quote from the manufacturer it adds about 1% to the project, not much from a % point of view but $ wise, harder to justify.