A Basement floor without concrete

[Rick JT]

The November 2016 issue had an article by Steve Demetrick and Steve Baczek on a basement floor that didn't have a concrete slab. Instead, it consisted of 2 layers of Advantech subfloor on top of 6" rigid foam, supported by compacted stone. Do the architect or builder have any further experience with this assembly? Anyone else attempt something similar?

[m beezo]

I remember the article and my first reaction was there was no way that would work, no way it would pass code, etc. I know that out of the box thinking is hard for us to accept and it would be good if there was a follow up on it to see how it is working, how the homeowners feel about it, has it it been done more than once so we know that it could be done again and what they are learning about the system as they continue to install it.

The trouble with the magazine and this forum is that there seems to me, to be a disconnect between the two. I have commented on several articles over the years and it seems that often the original writers of the articles never show up to discuss them with us. That seems to be something that I would like to see changed. How you get ahold of the guys who wrote the articles could be done by us but it seems there should be some notifications by someone at Hanley Woods saying show up on the forum to discuss the article.

[Ted S.]

There is such a thing as wood foundations, so think this could work. I don’t know why you would not just do concrete over ridged foam, however.

[Dick Seibert]

There is such a thing as wood foundations, so think this could work. I don’t know why you would not just do concrete over ridged foam, however.

Yeah, but they used to make airplanes out of wood and canvas, but that was a long, long time ago. As a kid I was a cadet and flew up and down the coast in a Bamboo Bomber, Roosevelt told us that there were evil Japs that had escaped the concentration camps, never did spot a Jap but heard stories of others who had seen them.

[m beezo]

There is such a thing as wood foundations, so think this could work. I don’t know why you would not just do concrete over ridged foam, however.

Ted,
I have heard of them but never seen one. Have you seen one? I see enough problems with concrete foundations so have to wonder about wood foundations. I would like to see some more info on them also, not that I am going to build a house anytime soon.

[Ted S.]

Ted,
I have heard of them but never seen one. Have you seen one? I see enough problems with concrete foundations so have to wonder about wood foundations. I would like to see some more info on them also, not that I am going to build a house anytime soon.

Never seen one. Although they are permitted, not sure what the motive is to pass on concrete

[johnny watt]

We built a few wooden basements back in the 80's as part of kit homes. They used marine grade pressure treated...the good stuff...before they changed the recipe. No such thing as Advantech back then, but that isn't even as resistant as the lower grade of PT wood. I will say those wood basements seemed comfortable when they were new...less damp, less radiant cooling, less echo. Of course if they ever flooded, it would be less confidence that things would ever dry out before things grew and rotted...at least compared to concrete.

Regarding the other detail...I have asked the green builder tree huggers to justify their slab insulation thickness specs, here before and they can't. They just pull the thickness spec out of their ash, using the "more is better" theory.. Also, most people I talk to prefer to spray foam in place before placing slabs instead of using sheets and trying to get things level enough so sheets don't get compromised.

[m beezo]

How do they ever get the spray foam to be level and even? I have had spray foam done only a few times but no one ever is able to get it smooth until they saw off the stuff. Even then in one stud bay it may be hanging out here and need cutting and a little under filled within inches of the stuff that has to be cut off.

I have always been a little skeptical of foam and it holding water.

[JonnyAtPhoenix]

I can't imagine ever recommending wood/foam for this application...

[Catspaw]

I did a variation on this at my house. I dug out a crawl space under a porch to make a more usable storage area. I wanted a floor that was cheap, flat and reasonably sturdy.

Concrete slab was too expensive.

I used gravel, a layer of foam, a 6 mil vapor barrier and one layer of Advantec. I caulked the seams and edges and primed and painted it.

It makes a fine floor for a storage space and was by far the cheapest of any of the options that I was considering.

[m beezo]

Cats,
I would have to understand the cost of concrete a bit more to know if the floor mentioned in the article would have been cheaper.In your case I can see it.

I recall the article and it seemed a lot of detail went into the floor as well as quite a bit of materials. I seem to remember layer of gravel, compacting the gravel, leveling things, then something like 2 layers of foam, then maybe the wood flooring, maybe two layers. They were dealing plumbing and support posts to go over and around so I know that had to take some time. The main thing I see is that when you are done you have a floor that you could easily do just about anythng you want with it. Carpet, hardwood, etc.

[Hety1983]

I couldn't imagine building a basement floor out of wood or foam!

[Catspaw]

I recall that the primary reason for them was to avoid introducing a ton of moisture into a very tight house.