Insulating exterior basement wall above ground


Old 01-16-12, 06:41 PM
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Insulating exterior basement wall above ground

I had my basement excavated and waterproofed and I had them put 2" insulation up against the foundation at the same time. Now I am thinking about the remaining 30" of the basement wall that is above grade. I'd like to extend the insulation up to the siding. Not sure the best way to go about this. I want to make sure I dont invite termites or carpenter ants. I already had a problem with carpenter ants once. I am looking at foam board but not sure how it should be attached to the wall or how to cover it. Since this will stick off of the wall probably 2" I need something to make a transition from the siding. I was thinking something that would look like a stone ledge like they use if they put up fake stone. Just not sure how I would attach it. Will I need to install some flashing under the bottom row of siding? Any thoughts ideas or pictures?

By the way the basement is a workshop. If I put the foam on the inside I would have to cover it with sheetrock. Not looking to do that.
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Old 01-16-12, 07:38 PM
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Bugs don't eat the foam, but they sure do like to nest in it. If you don't want to go with the fake rock, a pressure treated board with a slope on top could be anchored into the foundation and capped with metal trim. You could move the PT wood down to accommodate the rock above it as well and install the foam below. Another ledger below the foam would then give you something to install a covering to for protection and sealing from the critters. Possible a stucco covering for finish.

There are some pet friendly pest treatments that could be used seasonally to hold off the nesters.

Old 01-16-12, 08:56 PM
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Is all the PT wood necessary? Is it possible to attach the rock and stucco to the foam? I see the rock is actually called a watertable or water sill. Watertable / Sill

Is the watertable sufficient to block termites from tunneling directly from the foam to the wood? Is a flashing required under the siding and on top of the watertable to prevent water from running down behind the foam / watertable?
Old 01-17-12, 02:14 PM
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Insulating the exterior of the wall and keeping the thermal mass on the warm side is always better if you can do it but how to protect the foam above grade is the issue. I have not seen a good solution yet. Either way you will need to provide flashing at the base of the siding if the foundation insulation/finish system projects out farther than the existing siding. Dow used to make a system of boards with factory applied cement stucco that you could place on the wall, caulk the vertical joints between the units (4'-8" wide)and bury just below grade. However I believed they pulled it off the market because the stucco covering did not hold up to direct contact with the soil. I keep asking the "Passive home" people how to address the issue of foam exposed above the foundation and they do not have an answer that makes sense. They recommended covering the foam with stainless steel sheets, not likely to work in your situation considering the amount of exposed foundation wall. good luck and keep us posted if you come up with a good solution.
Old 01-25-12, 12:12 PM
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I am trying to solve this same problem.

Foam to concrete, special glue + a ram-set-nailgun using 3" nails that come with washers, you can set the depth.

How about copper roll flashing $$. It can be turned a nice green patina with a mixture of acid & salt (non-iodized)

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