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Basement Finishing

 
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Old 03-03-2019, 01:28 PM   #1
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Basement Finishing


Hi everyone,
Preparing to finish my own basement, and came across an insulating issue I've never had to deal with on other jobs. The basement is all concrete, with 1" rigid foam already on the walls, then a concrete and wood 'stud' support every 24". I have an open trench French drain around the perimeter of the entire floor, which will be behind the framing once its completed. I started using faced fiberglass along one wall but then got concerned about moisture that may come up from the ground and/or from the trench, which stays MOSTLY dry but has a few areas that gets some water. Here are some possibilities I came up with, but am looking for guidance. We are on a budget, but also dont want to cut corners that will result in major issues (like mold) in the future.
Am I safe to stay with the faced fiberglass? I could install return grills around the basement to allow the inside of the walls to breathe?
Should I change the type of insulation I'm using to rigid board or unfaced?
Should I insulate the framed walls I will be building instead of the foundation walls?
Thanks in advance!
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Old 03-03-2019, 01:42 PM   #2
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Re: Basement Finishing


I would remedy the source of water, top the trench with something impervious to moisture, and used unfaced insulation in the cavities (peel off the face), because you already have a moisture barrier in the foam board.

Take care of that water, if you can.

Giving it a means to dry from wall grills, etc, isn't a bad idea.

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Old 03-04-2019, 05:43 PM   #3
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Re: Basement Finishing


There arent any specific water issues, I'm just concerned about moisture coming from the concrete along the base, since there's the rigid foam already on the walls. And the fiberglass trapping that moisture and it leading to mold
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Old 03-05-2019, 08:21 AM   #4
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Re: Basement Finishing


Quote:
Originally Posted by Batchy View Post
Hi everyone,
Preparing to finish my own basement, and came across an insulating issue I've never had to deal with on other jobs. The basement is all concrete, with 1" rigid foam already on the walls, then a concrete and wood 'stud' support every 24". I have an open trench French drain around the perimeter of the entire floor, which will be behind the framing once its completed. I started using faced fiberglass along one wall but then got concerned about moisture that may come up from the ground and/or from the trench, which stays MOSTLY dry but has a few areas that gets some water. Here are some possibilities I came up with, but am looking for guidance. We are on a budget, but also dont want to cut corners that will result in major issues (like mold) in the future.
Am I safe to stay with the faced fiberglass? I could install return grills around the basement to allow the inside of the walls to breathe?
Should I change the type of insulation I'm using to rigid board or unfaced?
Should I insulate the framed walls I will be building instead of the foundation walls?
Thanks in advance!
Different areas have different building styles. I can't picture the basement walls, you are talking about.

I have seen concrete walls, with studs every 24" that are pre-cast. They set them with a crane and bolt them together. They sit on washed rock. No footings. Then they pour the floor inside that.
But...I've never seen an open french drain, inside a house.

Can you post a picture? I know it doesn't answer your question, but I'm curious.
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Old 03-05-2019, 09:42 AM   #5
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Re: Basement Finishing


Heres what I am dealing with. I'm just concerned with any moisture coming up through the concrete on the inside of the trench. Any and all suggestions and opinions are welcome!
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Old 03-05-2019, 10:07 AM   #6
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Re: Basement Finishing


Cut foam blocks for the bottom 6" or so for each cavity. No more mold worry. Unfaced for the rest. Close it up and have a beverage.
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Old 03-05-2019, 10:07 AM   #7
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Re: Basement Finishing


Why would they leave a gap like that? Do you have radon issues where you are located?

That would have to be sealed here for radon mitigation alone.
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Old 03-05-2019, 10:10 AM   #8
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Re: Basement Finishing


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Why would they leave a gap like that? Do you have radon issues where you are located?

That would have to be sealed here for radon mitigation alone.
I'm guessing they removed 3/4" boards (forms) from the gap.
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Old 03-05-2019, 11:02 AM   #9
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Re: Basement Finishing


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I'm guessing they removed 3/4" boards (forms) from the gap.
You answered the wrong question, I didn't ask how, I asked why they would leave the gap.

I know why it is there, those superior walls move around and need some space, but leaving it open so that moisture, radon gas or critters to have free access to the building makes no sense.
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Old 03-05-2019, 11:09 AM   #10
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Re: Basement Finishing


Those are the walls I was thinking about. You know the wood strips are there, to act as a stud wall. One of their marketing items on how their walls are cost competitive.

Keep in mind you can't put regular drywall screws into those boards. They are treated.

As for the trench. That is wrong. Doesn't matter now, you are stuck with it. Personally I would seal up that gap. Moisture, water, mice, too much of an issue. As said above, radon could be an issue. If it's not now, doesn't mean it won't be in the future. I've seen alot of houses that have to get radon systems installed before they can sell.

You already have some insulation. That's another one of their marketing points. For me personally, I don't like fiberglass insulation in basements. I feel like it is a breeding ground for mold. Just my opinion.
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Old 03-05-2019, 11:14 AM   #11
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Re: Basement Finishing


Roxul
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Old 03-05-2019, 11:15 AM   #12
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Re: Basement Finishing


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Roxul
Is Roxul mold resistant? I assume so, since you posted it. I didn't know. I know I don't like to install it. Just kind of nasty to work with.
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Old 03-05-2019, 11:38 AM   #13
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Re: Basement Finishing


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Is Roxul mold resistant? I assume so, since you posted it. I didn't know. I know I don't like to install it. Just kind of nasty to work with.
Absolutely. No, rock wool ( roxul ) doesn't wick so bad and doesn't support mold growth.
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Old 03-05-2019, 11:50 AM   #14
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Re: Basement Finishing


Thanks for the replies...I do have a radon system in the basement already. How would you seal the crack/trench up? As I said, this is my own house, and while I don't want to cut any corners that will lead to a mold issue down the line, I am doing it on a budget for some finished space for my kids play room (nothing crazy over the top or fancy) which is why I started out with the fiberglass, figuring the rigid board preinstalled would be the vapor barrier. I was honking about sealing off the bottom with more rigid and continuing with unfaced fiberglass
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Old 03-05-2019, 12:48 PM   #15
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Re: Basement Finishing


Is it a "ready to rock", prefab basement wall, set on stone? I remember seeing it in Fine Homebuilding. Sure looks like they removed a form board. Could be where the water is coming from? Under the wall? I would think the prefab wall is pre,,, waterproofed. Might fill the gap with spray foam,,, You would still have expansion for the slab, and might stop the water. Just a guess,,,, Look for a manufacturers mark?
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Old 03-05-2019, 12:52 PM   #16
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Re: Basement Finishing


Is it 1x on a concrete stud? I wonder if you could fill he gap with sand, Portland mix, Unfaced insulation and drywall. That seems to be the design.

Last edited by tang; 03-05-2019 at 01:00 PM.
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Old 03-05-2019, 02:13 PM   #17
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Re: Basement Finishing


Right now I'm thinking PL-1. Won't be cheap. Don't use SL-1. It will drain out forever. Even a cheap silicone sealant would work. Might not stick as well as PL-1.
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Old 03-08-2019, 10:24 PM   #18
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Re: Basement Finishing


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Is Roxul mold resistant? I assume so, since you posted it. I didn't know. I know I don't like to install it. Just kind of nasty to work with.
I've switched to Roxull almost exclusively these days. Way easier to install and not much itching. The pink stuff makes me itch within 30 seconds.

I install it even if if I have pay the difference out of my pocket. Just like synthetic roofing felt. Its worth it for the ease of install.

It also doesn't absorb much water. I have some scraps in a wheelbarrow that got left outside. Looks just like when I left it there.

Thread hijack over.

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