huangyhg

rock siding on independent footing? will it work?
hi,
i've got a project with rock siding on the foundation. half of the basement is exposed, and half in mostly below grade. the exposed section will have rock siding all the way to the footing. we are trying to decide if for the unexposed sections we can compact the soil in lifts and create a independent footing for just the siding just below the frost line to keep from siding these section to the footing (expensive). the concern of course is differential settling. can we expect similar settling? is this risky, has anyone done this before successfully?
we can't anchor the rock to the basement because it has 7" of foam on the side, and no serious thermal bridging is allowed. there are however fiberglass rods every 2' feet connecting the rock to the concrete that keep shear between the wall and rock to a minimum.
is it possible to post a couple of sketches? will make things clearer.
i wouldn't do it. the soil compacted in lifts will still have some secondary settlement left. you are best to build up a concrete block wall from the footing to where the stone veneer starts.
yeah,
i've attached the cross section.
certainly the headaches of having an entire countinuous insulation outer shell aren't but growing. for temperate climates it must be simply too much, or as chuckingly it is said in a spanish saying "poner los arreos antes que el burro". for temperate climates, structural concerns prime over local temperature issues; point. yet the hunger more and more complication born of wordprocessor legislation seems insatiable. for the cases where such shell is required, we seem to be needing more and more structural grade insulations. in your case if you are to respect insulation at the base of the siding you may still have differential settlement; and if you take it in cantilever through rods or whatever you may be defeating the intent of no thermal bridges.
if the rock lies on the footing, you are right it will rest upon 4" of high density geofoam. the rock weight would be restrained to below the 1% creep limit. but yes i would settle about 0.04". question is, if we put it on its own footing, would we expect the soil settling to be tremendously worse. also, note that the whole house footing also rest on geofoam, so once it is loaded the foundation is expected to settle approx. 0.04" realative to the soil.
to avoid differential settlement you may take the load in cantilever from the structural wall. that's an option, for secondary settlement, there will be, as hokie66 says. if so, make the cantilevers strong enough to support the friction that may be coming from adherent soil.
complicated with all that insulation. i wouldn't build a house that way, or i suppose live in a place that required so much insulation. but that doesn't solve your problem.
by the way, where is your waterproof membrane? i like basements to be dry, whether or not the temperature is well controlled.
i have worked on similar projects where a stone veneer was added to an existing residential home. the existing strip footings were extended at the basement floor level, building a block wall up to just above grade level and then building the stone veneer up from the block wall. we did have insulation sandwiched in between the existing foundation wall and the block wall, however, less thickness than you have shown. we were not as concerned about thermal bridging as we only have a frost depth of around 4 ft. in this area and tied the block wall to the foundation wall using metal ties.
i would not build the footing at the location you have shown, too much chance for settlement on disturbed fill. i would make sure the foundation for the stone veneer is at the same level as the structure. additional insulation could be placed on the exterior of the block wall located below grade to minimize any thermal transfer.
with the amount of insulation on your detail, especially underneath the slab-on-grade, i presume this is being built in an area with a significant frost depth or perhaps permafrost (or perhaps this is a speciality type building)? adfreezing on the exterior of the block wall supporting the veneer should also be considered.
7" of foam! wow! where are you? the north pole?

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