Comments on: The Problem With Too Many Basement Walls

By: Norman W Bunn

Norman W Bunn — Thu, 11 Apr 2024 18:32:13 +0000

I did a few things during construction to help with moisture.
1) Prior to pouring the walls, I coated all the footings with Henry’s sealant to minimize wicking into the associated walls and piers.
2) I applied Ghostshield 9500 densifier/sealant to the slab and the poured walls before applying the dimple mat system.
3) Installed dimple mat to move moisture to the drain system.
4) I also sprayed all wood in the basement with a mold inhibitor and applied boric acid to the bottom plates to handle insects. This coupled with the boric acid infused cellulose insulation should keep the wood trouble-free going forward.
Five years later, no leak and humidity is easily managed. No pests of any meaningful quantity.

By: Dale Dellario

Dale Dellario — Sun, 07 Apr 2024 17:19:53 +0000

We lifted our house and had a big hole dug out under it. Fortunately there were no springs, just lots of hardpan. When we did the finish grade, I had some of the clay soil sloped up to the house before covering that with topsoil forming an uphill dam against surface water. We put four coats of the black, gets-all-over-your-clothes tar on the foundation, and then drainage mat leading down to the footing against which we had a perimeter drain covered in rock, then filter fabric, then sand, and pit run backfill. The drains lead to a 12″ diameter standpipe that we could put a pump in if needed, then a pipe from it leads to a downhill sump. After two winters, no water appeared in the standpipe so the dam worked. Inside we glued 1″ of XPS and foam sealed the seams, then built a studwall on top of the concrete radiant floor which sits on a 10 mil vapor barrier. There is a capillary break between footing and foundation walls. It is very dry in the basement…..belt, suspenders, garters, and gaiters….and an HRV. The stud wall sits a nominal 1/3″ away from the foam and is filled with rock wool. There’s R-20 foam under the floor. We got it at it’s very lowest cost in a decade, $30 a sheet. Now it is $55/sheet, and there were 75 sheets. I figured this would be considered new construction so no tax credit.

By: Andrew F Pisacano

Andrew F Pisacano — Thu, 28 Mar 2024 03:26:03 +0000

Great comment thread going here! So I have the black tar on the outside and closed cell spray foam on the inside which should prevent too much water vapor from coming in to my basement. They did a water diversion drainage and there shouldn’t be too much water trapped next to the concrete. And I have zone conditioning. And it’s brand new. I don’t have internet yet and don’t have the relative humidity in the basement. Musty smell is notable especially on rainy days. I assume a dehumidifier will be my next step if humidity measures high. Does that sound right? Thanks!

By: Allison Bailes

Allison Bailes — Wed, 27 Mar 2024 12:45:51 +0000

In reply to Galen Wa. Galen: Closed-cell foam is your best option for stone walls like you have.

By: Allison Bailes

Allison Bailes — Wed, 27 Mar 2024 12:42:52 +0000

In reply to Ryan.

Ryan: I’m not a fan of wood and fiberglass next to concrete, even if it seems dry. A poured concrete or concrete block wall can look dry yet be wet enough to add a lot of water vapor through evaporation from the wall. It’s best to put foam board or closed-cell spray on the wall first.

Here are a couple of good resources on how to insulate basements. The first is an article I discovered nearly 20 years when I was new in this field:

https://buildingscience.com/documents/guides-and-manuals/gm-read-this-before-you-design-build-renovate/view

The second is an article by Martin Holladay with an update on the issue of whether basement walls need to dry to the interior. It’s behind a paywall, so if you’re not a GBA Prime member, you won’t be able to read it, but here’s the tl;dr (too long; didn’t read): No, they don’t need to dry inwards.

https://www.greenbuildingadvisor.com/article/joe-lstiburek-discusses-basement-insulation-and-vapor-retarders

By: Allison Bailes

Allison Bailes — Wed, 27 Mar 2024 12:33:50 +0000

In reply to Jim Newman. Jim: As you know, basements should never be in the same zone with the floors above. The heating and cooling loads are too different for that to work. Zoning can be tricky sometimes, but that's an easy one.

By: Allison Bailes

Allison Bailes — Wed, 27 Mar 2024 12:29:08 +0000

In reply to William Hullsiek.

William: See this article by Joe Lstiburek from nearly 20 years ago:

https://buildingscience.com/documents/guides-and-manuals/gm-read-this-before-you-design-build-renovate/view

By: Allison Bailes

Allison Bailes — Wed, 27 Mar 2024 12:25:27 +0000

In reply to Barry.

Barry: The InSoFast panels have vertical and horizontal electrical chases built into them. It looks like they’re pretty easy to use. Here are some of their videos on that:

https://www.insofast.com/explore/playlist-electrical.html

By: Allison Bailes

Allison Bailes — Wed, 27 Mar 2024 12:20:03 +0000

In reply to Ron. Ron: I first learned about the hot knife method of cutting when I built a SIP house 23 years ago but didn't get on then. I've checked them out again and may do it this time. Can you tell me how bad the fumes are?

By: Galen Wa

Galen Wa — Wed, 27 Mar 2024 11:07:46 +0000

Unfortunately, my 1938 home has 22″ thick stone foundation walls. The original “finished” half of the basement was simply plaster spread directly over the stone with minimal electrical receptacles located in the basebaord trim. The unfinished half of the basement, the foundation walls are far to rough for your system.

While the basement does smell a little musty sometimes, there have been no visible water intrusions since we bought it 2 years ago. I will mostly likely end up spray foaming the walls and the foundation sill with closed cell foam, then using batts in the framing.

By demoing the old gas-fired boiler and radiators and gas fired water heater and installing a three-zone heatpump and installing a heat pump water heater in the attached garage, I have picked up an entire 12 x 12 room in the basement, for my bike shop.