Concrete "sandwich" wall


Anyone ever use poured-in-place concrete walls with insulation in the center? Essentially 4" concrete + 2" insulation + 4" concrete. Much thicker is possible as well.

There are several companies out there that provide the non-thermal bridging connectors that tie the inside thickness of conc. to the outside thickness.

This basic technique was done in the 70's on residential basements, and is coming back into use again. I'm looking at it for a small comm. building, single story 24' tall volume.

The idea of it sounds good: Load bearing, provides interior and exterior finish surface (that is, if your client also enjoys concrete), excellent thermal properties (closed cell insulation at thicknesses up to 10"!) vapor barrier, fewer trades involved and pretty quick construction process.

We have some great concrete guys, so that part is not likely a problem. Still, not looking to "introduce problems" into the project. And, I have no idea how it compares price-wise with other wall systems.

Any thoughts / experience?

Apr 2, 09 5:31 pm

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have you thought about inverting the construction of that wall? i usually try to use ICF's for foundation walls, but i know people use them quite often for regular exterior walls.

really, it does the same things you are talking about here, but it gives you alternate options for the finish materials on the interior/exterior faces of the wall.

i know they make precast insulated concrete panels like you were talking about...never really heard about it being done on site (that i can remember off-hand).

Apr 2, 09 7:25 pm

thanks, ArchiTED, I've seen that system. Not really what I'm looking for, though.

Actually, I need to see the concrete on the interior and exterior. I NEED it, man... I love concrete. Durabilty and fire resistance are also important, as is an actual, unbroken thermal envelope -- all are characteristic of the system I've described.

Apr 2, 09 8:57 pm

kurt, have you ever looked at Ando's concrete wall detail?

Apr 2, 09 9:38 pm

offhand, i know this is covered in the detail construction atlas on concrete...

i think you mean something like this:

olgiati's school house in paspels (CH)

the inner leaf is structural, the outer leaf is suspended off the inner leaf w/ some massive steel studs.

Apr 2, 09 10:02 pm
Apr 2, 09 10:03 pm

Seems interesting - you would definitely need to provide a path out of the cavity like holz showed to deal with condensation.

Apr 2, 09 10:08 pm


you should look into precast panel walls from Duratek or another supplier. I have used the on jobs with no problems. You can do quite a bit with finishes and installation is really straightforward and fast. As a bonus (depending on your perspective), the panel suppliers will do the design of the panels in house, so they are easy for your engineers to spec. as well.

Apr 2, 09 10:20 pm
won and done williams

i remember you posting that detail on another thread, holz, and not to be an ass, but i still think that is one of the most cartoonish details i have ever seen. okay, there's some insulation there to avoid thermal bridging, but no, it doesn't seem to take into account condensation, there is absolutely no indication of what is structural and what is not, there is no regard that this is a lintel condition, the window frame detail is overly complex and looks like a cut from a manufacturer's catalog without imparting much real information. it's potentially a cool detail; i just have no idea how it actually works.

Apr 2, 09 10:30 pm

cartoonish or just Swiss awesomeness?

Apr 3, 09 4:26 am

Have you thought about doing this "sandwich" panel as a tilt up? I would think that would be easier than doing cast in place. The precast guys always make their panels in a bed so I'm sure it can be done. Would take more time than standart tilt, but still probably save time over a very complex CIP system.

Is the reason you aren't looking into precast because of the relatively close together control joints? I've often opted for tilt up just to avoid all the CJ's which look quite ugly when going for a perfectly flat surface. There are some pretty funky designs that you can do with precast these days though.

Apr 3, 09 8:31 am

look up fabcon. here you go...

Apr 3, 09 9:12 am

good call spark,

that is the other company I was trying to think of last night. I have worked with them in the past, they were very easy to deal with.

Apr 3, 09 9:27 am

i have just recently worked with them as well
they arent bad, but its more industrial of a look it seems, at least that is what i was using it for

what kind of project is this for?
the Fabcon panels are good for larger runs of walls, since it goes up much easier and less labor intensive than block walls

for example
the one i am working on now, is 800'x400'
so to do that in block wall, would have been way too much labor

but for a smaller project, house size or so, i dont know if the cost of this precast panel is worth it

Apr 3, 09 11:01 am

that air barrier makes all the difference to insulate the 2 separate masses and let you control better the energy you put into the interior walls while insulating from outside temperatures

Apr 3, 09 11:42 am

Great input, all ye tech geeks...thanks!

Tilt up is an option with this type of system, Aqua -- good points on the joints as well.

eCoDe -- I love Ando -- and, as architecture, that's definitely an awesome standard to shoot for -- was there a particular detail you were referencing?

holz, I can't tell on my screen -- is that a jamb?

randomized, that's what I'm talkin bout... I vote for "Swiss awesomeness"... poured in place concrete has it's own sublime quality.

jafidler and Janosh -- condensation...great thought. Here's the thing: The ins. is closed cell, eliminating the air space necessary for condensation to occur.

Apr 3, 09 12:17 pm

kurt, no I don't have a particular detail to reference. But it is typical for Ando's works to employ concrete as structural and finishing material, even you can see the ceiling is concrete. Actually I am curious how he did this. If I found some pics I will share with you here.

Apr 4, 09 12:12 am

Hey Kurt... whether the insulation is closed cell or not, it seems to me if the concrete is at all permeable moisture is going to migrate either from the interior or exterior and hit its dew point at the insulation portion of the wall and will need to be provided a way out so it doesn't have to find its own.

Apr 4, 09 11:59 am

houseofmud -- high mass walls are interesting in the way heat phases it's way gradually through the thickness. With the sandwich, condensation does not occure because there is not a large enough heat vs. cool interface at any point in the wall.

Apr 4, 09 7:52 pm

try Oasis wall system....

superior wall is another, but you still have to finish that on the inside.

Apr 4, 09 8:39 pm

Kurt, that's true for monolithic adobe and concrete, but the insulation cavity is going to create a temperature discontinuity across the thickness of the wall. For example, in double wythe CMU walls with a similar section, it's conventional to weep the cavity.

Apr 4, 09 8:51 pm

depends what the climate is like i suppose.

i do know that ando did a double wall in chicago and assume it works. you can probably find a detail of it in one of his details books...

also, just for comparison, peter zumthor did a similar detail for the thermal bath at vals, with stone and concrete sandwiching insulation. it looks much like the example holz provided above. it is absolutely technically feasible even in cold climates, but probably will require some research...

jafidler, not to be an ass either, but simply because a detail looks simple does not mean it is insufficient. no wonder europeans are always grousing over how american architects over-design everything ;-)

Apr 4, 09 9:41 pm

kurt hit the nail on the head -

ando uses closed cell insulation between the concrete leafs when needed (vitra, eychaner house) and then zero insulation at others (church of light)

the insulation has no gaps or voids and is continuous vertically, and as in situ is less porous than brick or CMU, there typically aren't moisture issues.

patrick gartmann's obsession w/ monolithic walls in historic buildings led to his house in chur that doesn't have separate layers but integrates expanded clay and expanded glass pellets for insulation. the result is no rendered facade, no plaster, no metal flashing and a ridiculously clean look...

Apr 4, 09 11:29 pm

but holz. doesn't your wall become like 60cm/2ft if you want good insulation? depending on the climate of course.

...kurt...Check out Detail magazine 2006 Bauen mit Beton aka Concrete Construction.

Apr 5, 09 4:42 am

Good tech points holz -- and as usual, you come up with great photos referenced from that library brain of yours...

Thanks for the link, randomized... For your wall thickness question -- usually nowhere near 2-foot walls are typically required. I'll post a link, but the R-value with 4 of insulation is in the 30's, due in part to the efficient way the composite wall works.

As I said in my original post, sandwich walls work -- it's a sound technology and that part isn't really in question. Thermomass is a company that offers the insulation and the non-thermal bridging wall ties (I think that company's corporate HQ is waaay off the beaten path). There are at lease three companies offering the same thing. These companies didn't invent the sandwich wall, but they've perfected many application aspects, and have lots of research posted.

Jump, thanks for the input... any photos? I read your comments on the "concrete finishing" post with much interest, too.

Apr 5, 09 8:01 am

kurt, i did a quick search on google for images of section but couldn't find any. i have the project in his recent book on housing but again nothing really revealing. my guess is that holz has the goods, or similar...he always does, somehow.

Apr 5, 09 11:32 am

kurt, had to look it up:
In Gartmann's house there's a monolithic concrete roof of 600-650mm and a monolithic concrete wall thickness of 450mm. And the details look even more cartoonish than the detail of olgiati's school house in paspels (CH)

Apr 5, 09 11:37 am

Wow, randomized -- a 2 foot thick roof? Solid? What would that be for? Check out the Thermomass website for some details that are built pretty regularly... walls of the thickness you're describing could conceivaby have astronomical R-values, beyond necessary in the continental US... but maybe you're not continental.

Jump, I was really more interested in your finishing experience, form types, etc -- most folks here don't have much poured in place experience when it comes to concrete being the monolithic inside and outside finish surface. Partially why many are suggesting precast, which is great for many purposes, but not what I need. I've got a boatload of tech details for sandwich walls... so I was interested in input from cats like yourself who've worked through the process of forming poured in place concrete...

In the end, I'm trying to use the sandwich walls an inexpensive, thermally superior, load bearing technique to get toward something aesthetically unique.

Apr 5, 09 1:00 pm

you really don't need to go so thick on the concrete mass as i see some of these doing. see STRATA
1/4 inch gfc over a monolithic EPS system and all the possibilities in between, and even with earthen-crete

but a variable thermal lag if measured and used in respect to solar orientation and employed will provide you ideal energy efficiency benefits.

Apr 5, 09 6:31 pm

i see, Kurt.

well, as far as it goes, we just use standard (for here) painted plywood formwork. it is painted with a hyperglossy coat so comes out beautiful. no special joinery is required for corners or for complex geometry. the carpenters sometimes do bits and pieces on site but usually we are careful to design the building to fit the module of the panels and have all work prepared off site. workers just assemble the parts. this means lots of review in advance but on site things go very fast.

if there is lots of steel we consider additives, but otherwise the mix is pretty regular. if we want to get a very perfect finish then we are careful to do oversight when they are vibrating, but even then there are bound to be areas that don't come out. as i mentioned earlier we have used the same repair crew that ando uses (yes his concrete is not always perfect either), and when they are done you can barely tell there was ever a problem.

but mostly we rely on the contractors who have staff that know what they are doing.

finally we coat the finish with a clear urethane that keeps the surface clean.

we do not however expose the interior surface because we need to insulate. with mositure content so high in tokyo we don't use VB so the walls can breath and the detail is thus pretty straightforward. if we did do a double wythe i would consider the system discussed above, but so far we have not had a client who could afford it. concrete is expensive here.

Apr 5, 09 7:48 pm

Thanks, jump -- very interesting about the process prep you do on your end.
You use Ando's same crew -- that's bonkers. Plus I agreed with your other comments on avoiding "perfection" -- sure, no giant voids and spalls, but the "natural" character is always intriguing and what I'll be going for -

Apr 6, 09 9:51 am

no worries. hope it is useful.

project prep is most impt for us. non-standard sizes are not difficult, mind you, but everything looks better if we plan the panel joints and location of tie-holes in advance. same as doing a brick building, or tile for that matter. life is just easier if all units can be divided by the module of the finish material.

if we plan to expose the concrete on the interior then we show the ties on interior elevations as well, just so there are no surprises. then again we are maybe a bit anal that way. we also plan location of all switches and plugs and mechanical equipment, etc. those things get done even if we don't pick the exact location, but often the results are not so nice...

out of curiosity, if you do the sandwich construction do you use regular ties, or is there a different system?

Apr 6, 09 6:45 pm

Thanks, jump -- VERY useful... and the interior planning you're describing is also well worth noting...
There are at least three companies offering the insulation and tie system for sandwich walls, but the only one I've pursued so far is Thermomass. I got a sample of the ties -- pretty clever, really. They're nylon, so they minimize themal bridging, but they have like 120,000psi tensile strength. They sort of twist and lock and you're good to go.

Apr 6, 09 9:54 pm

Super old thread, but it came up when I was looking up CIP sandwhich walls.

Check out Thermomass.  We used them in Precast, but the CIP looks like a very promising option and they have cad details.  Plus, the whythe connectors are thermally broken.

Nov 8, 18 8:41 pm
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I currently have an 18 storey building under construction using precast sandwich panels. 6 to 8 inch interior concrete structural wythe, 4 inches of EPS, 3 inches of concrete cladding. TONS of detailing in shop drawings but a durable, quality product in the end.

Nov 9, 18 11:09 pm

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