cast in place walls with internal insulation; thin walls/cols
cast in place walls with internal insulation; thin walls/cols
(OP)
In a single-family residential project, we're considering use of a cast in place concrete wall system where there are a couple of inches of rigid insulation embedded in the center of the wall forms. In effect, if we had a 8" total wall thickness, we'd have let's say 3" concrete face, then 2" rigid insulation, then another 3" concrete face.
Questions:
(1) general thoughts or experience with this system
(2) any way to get the system to behave more like an 8" solid wall, instead of two 3" concrete faces? The hope is that this system might be able to carry vertical loads from above.
(3) how to accommodate concentrated loads at the top of this wall, like where a concrete beam is supported at the top of the wall. One option might be to not use insulation immediately below the concentrated load, using 8" solid concrete all the way to the ground (could be a couple of feet in width). Another thought is to fill in a solid area immediately below the concentrated load, like how you might grout solid a few cells in masonry immediately around a concentrated load, but the solid area doesn't extend all the way to the ground).
(4) on a related question, how thin are people typically comfortable with for a solid concrete wall (ignoring the internal insulation question) for 2-story residential construction? Assume I have a better-than-average concrete contractor. Also assume I want to bear concentrated loads from concrete beams on top of the wall.
(5) how skinny/practical can I make a concrete column, assuming it's lightly loaded, not exceptionally slender, etc...8"x12"?? Of course I know it depends on the loads and slenderness ratio, but I guess I'm trying to determine what the practical limit might be for good quality residential construction.
Keeping my fingers crossed for not overly conservative feedback ;)
Questions:
(1) general thoughts or experience with this system
(2) any way to get the system to behave more like an 8" solid wall, instead of two 3" concrete faces? The hope is that this system might be able to carry vertical loads from above.
(3) how to accommodate concentrated loads at the top of this wall, like where a concrete beam is supported at the top of the wall. One option might be to not use insulation immediately below the concentrated load, using 8" solid concrete all the way to the ground (could be a couple of feet in width). Another thought is to fill in a solid area immediately below the concentrated load, like how you might grout solid a few cells in masonry immediately around a concentrated load, but the solid area doesn't extend all the way to the ground).
(4) on a related question, how thin are people typically comfortable with for a solid concrete wall (ignoring the internal insulation question) for 2-story residential construction? Assume I have a better-than-average concrete contractor. Also assume I want to bear concentrated loads from concrete beams on top of the wall.
(5) how skinny/practical can I make a concrete column, assuming it's lightly loaded, not exceptionally slender, etc...8"x12"?? Of course I know it depends on the loads and slenderness ratio, but I guess I'm trying to determine what the practical limit might be for good quality residential construction.
Keeping my fingers crossed for not overly conservative feedback ;)






RE: cast in place walls with internal insulation; thin walls/cols
There is a wide range of availability of technical support. One of the most common with a good technical, design and installation support is the Rewards system (no connection to me), but there are some other good ones. There are also some lower level form producers that concentrate on making meat trays for the Walmart meat department instead of technical/design support.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: cast in place walls with internal insulation; thin walls/cols
RE: cast in place walls with internal insulation; thin walls/cols
RE: cast in place walls with internal insulation; thin walls/cols
Sandwich panels are commonly used in the U.S. and internationally. The key is to have adequate ties between the two exterior layers to create a composite wall section.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: cast in place walls with internal insulation; thin walls/cols
We poured a recent sandwich panel wall in Wisconsin in the vertical position for an industrial project and it came out well but you must use the proper ties and sufficient thickness to be able to properly place the concrete.
RE: cast in place walls with internal insulation; thin walls/cols
RE: cast in place walls with internal insulation; thin walls/cols
RE: cast in place walls with internal insulation; thin walls/cols
I would discuss rates of pour with your ready mix supplier along with the admixture supplier. If you have never done this construction before, I recommend pouring a test panel to work out some of the issues first.
RE: cast in place walls with internal insulation; thin walls/cols
RE: cast in place walls with internal insulation; thin walls/cols
Look at PCA-100 (for ICF's) to get an idea of the capacity of such a wall without calcs.
There are sandwiched foam systems which have the shear ties, but you are now raising the cost, since you are buying a somewhat expensive system AND paying for forms.
The benefits of ICF construction includes the thermal mass being insulated from temperature swings, and the near absence of forming costs beyond the ICF itself.
Having the concrete mass of the exterior could be beneficial to avoid additional cladding costs if exposed concrete is the look you want. Exposed concrete could also as a passive heat collector for warm days and cold nights, but then insulating inside the concrete would negate the benefit.