I’m researching the type of construction we want for the foundation of our new house (spring 2011). The basic concept will be a simple 2-story rectangle (26’x38’). I know many people like ICFs, and I do too. But I’m wondering about the cost vs benefit of a ICF vs CMU with 2” ext. XPS. I’ve been told that the poured (ICF) wall would be stronger. But a properly designed and constructed CMU wall should be plenty for typical residential structures, right? After all they’ve been building with them for many, many years in my area. And while I would not do a CMU or ICF basement myself, I believe I could add the 2” ext. XPS to the basement wall before it is backfilled. In my case, initial estimates indicate that the cost of the CMU plus insulation would still at least 12% (and maybe more reasonably 15%) less than an ICF DIY (which I don’t really want to do…) Any comments or suggestions? Or reasons why a CMU + ridig ext.  insulation is a no go? Thanks

If you decide to do any finish work on your basement, that 12% savings on the CMU wall will disappear in a heartbeat. The additional framing required to finish CMU will more than use up your savings. I am sure that I prejudiced against CMU basements (I have spent too much time trying to make them usable), but I can't believe that even a 25% savings would convince me to use them vs. ICF.

BabyBldr,

I was in a similar situation several years ago when I was in the planning stages of building my house. I was looking at CMU, ICF, & poured walls. I live in Michigan, and in order to go with ICF for the basement, I would have to have the ICF basement walls drywalled before I could get my Certificate of Occupancy because the foam needs to be covered with a fire retardant or drywall. I didn't want to spend the money to drywall the basement at that stage and also didn't want my property taxes to be based on additional square footage from the finished basement. I came across Superior Walls precast insulated concrete foundations and had them give me an estimate. I was surprised that it was only slightly higher than the poured concrete estimates that I was getting, but the poured concrete estimates didn't include any insulation... Superior Walls has R-5 built in, and allows additional insulation between the concrete studs that are 24" oc faced with a wood nailer to hang drywall if you choose to finish the basement. This will save you time and money if you ever decide to finish your basement, since you don't have to build wood walls around the perimeter of the basement. I haven't finished my basement yet, but hope to soon.

It's true that here in Michigan we have installed many CMU foundation walls, but it is equally ture that they are seldom used anymore. About the only place we still see them are areas where concrete contractors are few and far between, and usually too poor to afform a set of forms. The people in the area are also usually too poor to afford cast in place (CIP) concrete.
CMU walls are more than adequate to carry the compressive loading of a home, but to bear the lateral soil pressure of anything other than sand requires significant improvements over what is typically done residentailly. That is why you will notice many bowed CMU walls, and that is why the industry has moved to CIP walls. Thus, I would compare ICF to CIP with insulation.
If you do plan to use CIP with 2" of foam, be sure to mechanically fasten the foam to the wall to avoid gaps, which make it a pain to coat. Don't stop the foam at grade (as is quite tempting) but continue up to the top of the wall. The area above grade is where the greatest heat loss is. Be sure to have a plan to cover the foam, and accomodate the 2" difference in size of the foundation versus the house.
Superior Walls aren't a bad option at all, but you will still need to add insulation later if you finish.
Pay me now for drywall or pay me later for insulation and drywall.
I have a comparison of popular below grade wall systems at:
www.rvaluehomes.com/comparison.cfm
Jake Vierzen
R-Value Concrete Structures

Thank you all for the information and input, it is so helpful.

Jere noted in his circumstance that Superier Walls allowed him to put in the basement but leave finishing until later (no drywall for C.O. and no 'finished' space in the tax assessment). That has apeal to me too, since it may be many years (or never) before I finish the basement. I believe in PA where I am, the same sort of thing would be true relative to needing to drywall ICF (for C.O.) vs doing nothing to the Superior Wall. I'm wondering - just curiious - why is that? Is there something about the type of insulation on the ICF that requires it to be covered vs the blue board type of insulation you see on a Superior Wall?

Thanks!

I would be careful to about using a CIP basement system like a superior wall. I would at least consult an engineer, especially if you are fortunate enough to know one. Superior walls normally are not very thick and advertise that the increased strength of concrete (5000 psi) offsets the cost of additional material. I am a little speculative about that...if that were the case why wouldn't poured concrete wall guys do the same thing?

Just giving advice and not trying to completely know the superior wall...though on the other forums its been done before!

Renangle,

Superior Walls are built off site in a climate controlled building, not cast in place on site. Is this what you refer to as CIP? Once the panels are built, they are delivered to the site by semi and set with a crane. The total wall thickness is 10 1/4", not including brick ledge. You don't think that is very thick? That thickness is made up of concrete studs placed 24 o.c., 1" DOW foam board, and a 1 3/4" concrete outer face shell. There is a steel reinforced top bond beam and footer beam. The 5000 psi concrete is the minimum strength. The basements are engineered custom to that particular house plan and can allow for extremely high point loads by adding additional concrete studs.

When I was looking into Superior Walls for my basement, I took a tour of the Superior Walls facility in Michigan and saw the whole process. They mix their own concrete in their facility, so they can control the mix, amount of water, etc.. By using less water, this allows them to achieve much stronger concrete. They test their concrete often, and it was holding up to 8000 psi, sometimes 9000 psi before failing. Take a look at their website for more information www.greatlakessuperiorwalls.com

Jere,

You were correct that I misspoke when I mentioned the CIP or Cast in Place, I had meant to say Pre-cast.

You are again right that a superior wall is pre-cast and does use a higher PSI concrete. I am happy that you like their product, I merely advised the person in Pennsylvania if they have access to an Engineer then get their opinion before moving forward. Their website says 5000+ psi, so that can be subjective.

Also, caulking as a waterproofing system at the seams only would have me a little concerned over time. They are guarenteed for 15 years...what happens on year 16? I'm not trying to throw them under the bus, I am suggesting that before he signs a contract to consult an engineer (especially if he knows one) to make sure its the best decision for them.

renangle

I am in Central New York and frequently bid ICF against Superior Wall. In fact, we finished an addition about a month ago with ICF against an existing Superior Wall. I will tell you that they might be 10" thick right on a rib but these were about 2 inches thick in between. I tried to dowel into the superior wall but there was no "meat" to epoxy our dowels in. We have to cut a doorway to connect the basements and I could do it with a chisel if I had to. Both myself and the homeowner agreed that going through the motions was destroying the superior wall and the ICF wasn't going anywhere. Further more, why must I build a 2ft.X1ft footing with (2) #4 bars chaired or hanging mid depth and verticles at least every 4 feet apart to get a footing inspection yet this Superior Wall is sitting on 4 inches of crushed #1 stone? There is no question in mine or my customers mind that this ICF addition is much stronger, more water tight, and better insulated than the Superior.......and the same price if I took out the footing (which I happen to feel is pretty important). In the case of "tying" the addition to the house, I think it would have been the other way around had we been able to do it. I think the house will move before the addition.
AS far as CMU/XPS, isn't there a risk of condensation and mold between the foam and CMU unless you seal it with a Xypex type product?

Renangle,

Having a structural engineer (or the architect that drew the plans) review the house plans, along with the engineering for the roof (if going with engineered roof trusses), and floor system engineering (if going with TJI's or similar) is a good idea. In my case, I have somewhat of an engineering background and was able to review the roof truss drawings and floor system drawings myself. The point loads are called out on the roof truss layout for roof loads, and the floor system engineer designs the floor system taking into consideration the roof loads. Most roof loads when using engineered roof trusses are designed to have load points on the exterior walls, but sometimes there are loads that come down on interior house walls. The floor system engineering plan also has all point loads called out and locations. I was able to forward engineering info. to Superior Walls and they engineered the foundation with the loads calculated from the truss and floor system engineers. They drew a 3d cad model for me to review and they called out the point loads right on their drawing, so for me to verify was very easy.

As far as the caulking/sealant (I think it some kind of urethane?) that they use, I was skeptical at first too. When I toured their facility, they explained that the caulking/sealant is actually stronger than the concrete. The only way to separate panels is cutting through the seam with a saw. If you try to pull them apart, the concrete will break before the caulking/sealant gives. They handed me a small piece and told me to try to pull any of it apart... I had no luck. At the seams, the run a thick bead down the middle, then join the panels bolting them together at the top and bottom, then apply a bead on the outside of the seam and inside.

With any basement system, you want to make sure you back fill with something that will allow water to drain down easily. You do not want clay, as clay holds water and doesn't allow it to drain down, so the water goes against the foundation wall, freezes in the winter, causing extreme pressure against the basement wall, causing cracks. This cycle continues until the cracks are big enough for the water to start seeping through and into your basement. I was lucky that my soils were mixed with sand, no clay, so that was sufficient for water drainage. The next house I build, I will probably have the excavator back fill around the foundation with all sand. My basement has been in the ground for 8 years now and I haven't had any leaks or issues what so ever... the only issue I have is I wish it was bigger! lol

I think that its great that you have had success with your project, but I am more of the opinion of EliteConcrete. I simply see it as agreeing to disagree and that isn't really abad thing in my opinion, that is why we have this forum.

EliteConcrete,

I see your point. Did you consult with Superior Walls to see what their recommended way to attach the addition foundation to the existing Superior Walls foundation and their recommended way to create a door opening in the existing foundation? With any product/system there are does and don'ts, there are preferred ways of doing things and ways highly recommended not to do. For instance, a heating a cooling contractor should not cut through an engineered floor system or lvl beams in the floor to run duct work without first consulting with the floor system company/engineer.

I may be wrong, but the reason Superior Walls is able to use less concrete in their foundations and use crushed stone for the footing is the 5000 psi + concrete that they use. Wood foundations also sit on crushed stone, Superior Walls is a similar concept, but use concrete instead of wood. At the tour I went on at their facility, they mentioned that approx. 60% of the crushed stone footing would have to be removed in order for the foundation walls to move.

Now if a foundation is using concrete that is 2500 psi max, on a good day, at the time the concrete truck leaves their yard, and travels to the construction site and pours the concrete into the forms, a lot of time has gone by where the concrete will start setting up unless more water is added. The more water that is added, the weaker the concrete becomes. So footings must be bigger, more concrete is used, and steel rebar is used to help strengthen the concrete. In the event the concrete cracks, the rebar helps hold it together.


Renangle,

This forum is great because you hear all of the different sides and opinions (kind of a check and balance)... from homeowners that have used a product and their experience whether good or bad, contractors/builders and their experiences with products whether good and bad, and salesman that want to promote their products/services by pointing out the pros of their product/service and all of the cons of a competitor's.

I (like most I presume) use at least a
6 bag mix with water reducer in walls.
My mix is 6.5 bags of Portland with
8oz./100 of Polyheed which makes
5000 psi on any day. So I should be
able to stop using footings and start
pulling some profits ;-)
As far as tying in, they had no recommendation
on the local level. For cutting the doorway,
they said don't do it over a seam.

hi all you can find stuff related to building insulation green buildings building orientation thermal analysis etc at www.energysmarter.blogspot.com

Hello,

I was that O.P. on this thread way back in May 2010. My how time flies! We have just gotten our construction drawings and currently spec’ a 9’ Xi Superior (precast) wall for a roughly 1600 sq ft basement. I met with a sales rep from the local Superior supplier, got to tour the place – it was interesting. A few questions linger in my mind and I’m looking for some input/comments. First, let’s talk about under-slab insulation and thermal isolation:

Note, the precast walls are supplied w/ R12.5 on them, and the sales rep seemed to recommend that the screed board all around the slab just stays in place. However, my drawings spec’ the removal of the screed board and filling with sealant for radon issues - we will also install a passive radon system & test after construction.

The house will be in south-central PA with deep soil temps in the 58-60 deg F range.

I asked about under-slab insulation and isolating the slab-edge from the pre-cast walls. On both counts, the sales rep said that the area builders don’t really do that (that the ground acts as a sufficient insulator at that depth)… no further details were offered on how I might do it.

What do you think? If you used a pre-cast wall system, how did you handle this detail?

I may be wrong, but it is my understanding that the concrete slab locks the bottom of the precast wall into place.  In fact, we were told not to backfill the walls until the basement slab and main floor were installed.  Now whether there can be a gap between the edge of the slab and precast wall should be answered by the engineer at Superior Walls.  I would not rely upon their sales people for this answer. 

Since my projects are in the Southeast, we did not insulate under the slab or between the slab and precast wall.  We let the basement slab flow over the bottom of the wall and into the wall.

All of the basement slabs I have placed with Superior were directly against the wall. I was told it locks it in. We lay blocks, pour walls and build with ICF here in NY
and can tell you with much experience that superior is not
Superior to ICF construction in strength or efficiency.
I for one would never put a house on walls without a footing. In fact, I am only required to use an 8" footing but we make it 12".

I just want to repeat a brief comment in an eariler post. ICF are a BAD idea for a UNFINISHED basement because the building code requires you to cover the foam with
drywall (or equal) for fire prevention. Once you have drywalled you now have a finished basement, high permit fees and higher property taxes.

The ceiling area has te be finished also for it to be considered "finished", but you are wright about the covering of the walls part.