Hi, new member here. My wife and I are about to build our first ICF house. I've gone through all 114 pages on this forum, and found lots of questions, advice, and information. Thanks for all who have contributed over the years! I thought it may be a good idea to have a thread devoted to lessons learned. What ICF experiences have you had that you would have done differently, knowing what you know now? This can be from the house-design phase, all the way through construction, and full occupancy. Thank you in advance to anyone that can contribute. Scott

Hello SRW,

First and foremost, make sure you check references on installers. There is a big difference between skill level and attention to detail available out there. If you are installing yourself make sure you have proper installation training. I don't know where you are located but we have a class coming up in January of next year in Fort Worth, Texas.

When I built my house about 9 years ago, I had completed about twenty houses or so but nevertheless, I was a little too focused on the ICF and anxious to get started with the walls. The ICF is actually only a small part of the process -- make sure you have thought through (or planned) the chronology of events -- e.g. if you have drainage to run from the back yard to the front yard make sure you complete all the preparation while you have easy access and are not crowded between your new ICF walls and your new ICF retaining wall. LOL. Having now trained many installers in commercial and residential construction I am a little surprised at how basic it all seems now looking back. In my case, I created more work for myself with hand tools when I should have used a Bobcat or a large trench digger.

Although it was not a problem for my home, sometimes I see installers using small levels to plumb walls - I suggest you laser up your corners (or use a six foot or better level). Also, don't think that compaction is just a commercial thing -- you will may need dirt compaction under your driveway etc.

Even if your installer has completed a hundred houses and can knock out a 3000 square foot house in a few days I would suggest that you spend a day checking everything carefully while it's easy to move and change.

Use ICF for your gables -- some installers don't like to do gables -- but they are easy and much better for a number of reasons than building a frame wall on top of an ICF wall.

Have your slab engineered even if your not required to do so because your out in the country somewhere. Your engineer might change the design some based on the ICF design and rebar placement.

Regards

Thanks, that's good information.

We wont' be doing the actual construction ourselves, but will discuss these things with our builder.

I don't want to focus on our specific build, but rather to create kind of a single-source repository for tips and suggestions that people learned from their own projects that they would chance if they could do it all over again. Keep 'em coming!

Scott

I did a DIY build, and there's not much I would change. I designed my own flared window returns to prevent a tunnel effect inside, and there are three windows I did straight. I wish I had done all of them flared. I also learned to plan ahead, and should have made more penetrations through the walls, even if I didn't use them. I had to drill a 3" hole for my mini-split install- that's a LOT of work! I hadn't worked out my HVAC system when I built the walls. Make sure you get a clean spare ICF block from your builder to show friends and family, as many won't have heard of ICF.

I wish I had done an all-steel roof structure with steel SIP's, but I doubt I could have afforded it. You didn't ask for things we specifically DO like about design decisions, but I'm glad I opted to go 7 courses high for 9' 4" ceilings.

Even if you don't do any work yourself, I highly recommend learning as much as you can so you can keep an eye on your contractor and subs, and ask intelligent questions. I frequent several house-building forums, and the construction industry seems to be rife with hacks who do poor work and don't follow instructions or blueprints very well. I KNOW that there are many, many good builders who are honest, hard working, and do excellent work, but there are also some who don't fit that description. If you can, visit your site often and make sure things look right. If the front door looks like it's out of place 3 feet, it's better to check before the concrete goes in.

I do like the idea of including things that you changed that turned out to be great ideas, also. I also changed the title of the post. Good suggestion.

And you're right about making sure there are enough routes to the outside. Going through 6-8" of solid concrete is something best to avoid. I'm working with the builder on some of that right now.

Scott

Things learned along the way.
Use ICF block that actually clip together. Nudura or Integraspec.
Use foam end caps at all openings. Cut panels for top and bottom.
Encapsulate all concrete in foam. Under and beside footings as well.
Use pvc or fiberglass windows.
Use Helix Micro bar reinforcement.
Use 100 mm slump and add 1 liter per meter of Super Plasticizer.
Shoot the pump operator if he can't keep the boom right on top of you (or the placer)
Use poly vb on the ICF behind the drywall even though it is not needed.
Use high heel trusses and keep the trusses 4" less then outside to outside of foam dimensions. Cover the heels with 2" of eps to underside of top chord.
Install a complete air barrier on the bottom of you trusses. If you don't know how, ask! Even better, add 2" of eps.
Renting a coring rig (if you don't own one) is cheaper than banging holes through ICF and better then making unneeded holes.
Some people have enough experience not to need an Engineer.
Most people who don't hire an Engineer, should have.
Insulate under the slab even if you don't use hydronic heat.
Hydronic heat is the nicest heat in the world.
ROI for hydronic heat doesn't always work out with a well built ICF home. Floors don't always stay warm if you don't need heat.
No matter what heating system used, do mechanical air exchange.
Use R50 for the walls when calculating the size of heating apparatus you need.
Put the biggest stove hood over the stove that you can. Not necessarily the most CFM's.
If you hire a contractor, hire one who is a good contractor first, if he knows ICF, that's a bonus.
If you do your own ICF, be willing to pay a tutor.
If you do your own build, give up a year of your life.
How many questions can you handle at once? You will be dealing with between 10 and 20 trades who need to know what is in your mind.
Pay for a top notch set of building plans.

If someone doesn't disagree with at least half of these, this forum is no longer up to snuff.

I'm interested in why a poly vapor barrier behind drywall.

I didn't do poly, but I did tape all of the ICF joints. I don't know if it did much but I did achieve a .59ach@50Pa. every little attention to detail helps!

Texas has it right. If you are acting as ICF installer/ GC do as much as you can on the front end. Changes made on the fly cost time and money. Get good subs. Working on an ICF job shouldn't make their bids come in higher. One thing I learned long ago is be wary of the low bidder. Sometimes they work out but when they don't it hurts the job. Stay in touch with the folks here. Lots of good intel.

The foam is a vapor retarder, but the ICF joints are not. I think the poly is more for moisture creeping up from the footings and in from the concrete along the ICF joints as much as it is for air infiltration. At any rate, a low cost layer, easy to place prior to finishing.

But at least in theory, with the AC on, moisture could condense on the plastic and then run down and out onto the floor . I'd much prefer that any such moisture be allowed to dry into the room (ie, breathable in both directions, ...). If the plastic can direct any such water below the floor or outside, then OK.

With ICF construction we put a lot of water between the foam layers. Even those of us who use low slump and water reducers still put a lot of water in there. When we fast track an ICF home, there is not much time for the water in excess of the rehydration needs to escape. When the drywall goes on and is taped and painted, there is still a lot of moisture in the concrete. This moisture tends to swell the 1/2" drywall to 9/16 or so. When it dries, it does not shrink back but the mud over the screws does, so you get small divots where the screws are.
By putting poly on the wall, you force all drying to the outside and the drywall is protected.

In fact virtually every house in Canada has poly behind the drywall. No puddles.

And in Florida, people who put vapor barriers on the interior side experience puddles and/or mold. Is non-ICF VB performance very relevant to a well air sealed but non absorbent (plastic sheet next to EPS) ICF wall - I don't know.

After the first year, the mix water moisture will have moved out of the wall.
An ICF wall does not have an open cavity that allows moisture laden air to circulate so where would the condensate come from?
Any moisture that travels through the wall can still dry to the outside.
With foam under the footing there will be no damp rising.

Skip sill at top of wall and use LTA2 more often, yes. Steel studs on interior walls, no.

Posted By ICFconstruction on 16 Dec 2015 08:45 PM
Skip sill at top of wall and use LTA2 more often, yes. Steel studs on interior walls, no.

Or use HAGAM-10 brackets to attach trusses.  No embedments to work around, just trowel the wall off level on pour day...

I could not find "HAGAM-10 brackets". We attach a short piece of 2x4 to the LTA2, and during the pour set them with a laser, no need to finish the concrete in-between.

Downspouts plumbed around perimeter and to day-light. Motion sensing soffit lights.

Sorry, keyboard popped an extra A in there. Simpson HGAM10. Simpson actually shows them on the same spec/diagram page as the LTA2 under truss connectors.

I used a doubled PT 2X8 on top of my 6" Fox walls, bolted with J-bolts anchored in the concrete. I used raised-heel trusses, and made them flush with the outside of the top plate. I used OSB sheathing on the outside, tying the plates to the trusses, and used H-10 hurricane clips on the inside. I needed the double plate to have room for the clips. I then put a layer of rigid foam on the inside and outside to bring the walls flush with the ICF, and create a thermal break. Our roof is overbuilt for our climate, but I spent 30 years in FL, so I'm paranoid about wind.