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dave11 10-28-2009 06:47 PM

Framing basement wall without covering top plate and rim joist
House was built in 1951, concrete block walls in the walkout basement. Walls are bare, I want to frame them and insulate, but I want to leave access to the top plates and rim joists. The reason is that in the past two years, I've had carpenter ants twice in the rim joists, in wood that was not ever wet, just areas of penetration for electrical and plumbing. I probably wouldn't have found the carpenter ants for a long time had the joists been covered by conventional framing.

Is there way to frame that accomplishes this? The typical framing method, namely nailing the top member of the new wall directly to the bottom of the floor joists, can't be done.

What about lowering the top member to the height of the block wall, then adding a spacer block of 1.5 inches thickness, to span the distance between the top member and the floor joist? This still leaves access to both the top plate on top of the block wall, and to the rim joist.

Or is there a special type of bracket that would accomplish this?

Any opinions appreciated.

jogr 10-29-2009 12:04 PM

Normally the bottom of the floor joists and rim joist sits on the sill plate so the walls wouldn't obstruct visibility of the rim joist and sill plate if you don't put on a ceiling (or a drop ceiling would allow you to open for inspection).

However, the biggest insulation gain you get in a basement is when you insulate the rim/sill plate area. Most of the block wall is insulated to some degree by being below ground level. So if you insulate the walls but leave the rim uninsulated you probably won't notice any improvement at all in the basement.

Your best bet is to first eliminate/fix whatever is causing the carpenter ant problem. When your sure that's fixed then you can insulate the rim joist area without concern.

dave11 10-29-2009 12:54 PM

The rim joists are already insulated with 2 inch thick foamular. It can be removed and replaced as needed.

But if I frame the basement walls, the tops of the studs have to attach to something. If I nail them to a top plate, and nail that to the bottom of the joists, then I've cut off access to the 2x6 on top of the concrete wall, and also the lower edge of the rim joist, where I've already had trouble with carpenter ants. So to avoid this, the stud would need to anchored at the top by another method. Either putting a 1.5 by 1.5 inch spacer between a horizontal member and the bottoms of the joists, or extending the studs, so they can run alongside the joists for a couple inches, and be nailed into the joists.

Carpenter ants have been rampant in my neighborhood for a few years, there's no way to guarantee they won't find a way in. The exterminator who treated the extensive trouble my neighbor had said people are always taking a risk when they cover any of the framing below or at grade, from both ants and termites. My neighbor had far more damage than I did because his basement was finished and framed so as to hide the top plates from view.

ARI001 10-29-2009 01:15 PM

You will still have access to the sill plate and rim joist using traditional framing methods. You would simply look over the top plate to inspect them. If you install a drop ceiling you can inspect for carpenter ants at leisure.

You can have your pest control company apply a preventative treatment such as Timbor or other borates to any untreated framing members. The sole plate for your basement framing should be ACQ or other pressure treated wood which will help to prevent termite infestations. You could opt for light weight steel framing which is completely termite and ant proof. You can also have your pest control company drill the slab and apply termiticide under the slab. They are supposed to stay 6 to 8 inches off the wall to avoid drilling into the footers so framing should not inhibit them in any way as far as treatment.

joan518 10-30-2009 12:16 PM

I have a log home, so I am always treating for something. Log home owners and suppliers use bora-care quite often which is a borate with a glycol. The glycol helps the borate to penetrate the log. I would suggest going to the Bora-care website (Nisus Corp.) or the perma-chink website for help in curing the carpenter ant problem. The bora-care lasts for the life of the wood and is a little stronger concentrate than the shell-guard product that perma-chink sells although they used to carry bora-care at one time. Good luck!

RobQuillin 10-30-2009 08:38 PM

Most of the carpenter ants that I have come accross is in an area that has a higher moisture content. This is one reason that they like areas where the wood is close to concrete. I would make sure that you are leaving an air space between your framing and the block wall. This will allow the wood to keep dry and make it a little less appealing for the ants. I would also make sure that the experminator does his best treatment before you try to cover the wall. Thirdly I would seriously think about metal studs. Ants don't like metal. From reading your post it sounds to me that the main problem is from the exterior. I would be more concerned about what was going on outside than further inside. It sounds to me like your caulk around the wall penetrations have leaks and let the miosture into the siding. You can check this by picking at the caulk and see if it pulls away from the siding anywhere. If it does pull away then it is just sucking the moisture in instead of keeping it out. This would attract the ants and once they are in they spread out. I would remove any faulty caulks and sealants from around your wall penetrations and replace them with a good tripolymer caulk and make sure that there is noplace for water penetration. If water can penetrate then ants can penetrate. If you seal them out then you should be safe in the basement.

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