Building Walls in Unfinished Basement

[jconnor3]

We are looking to finish the basement in our new house and i'm a little unsure what route to take for insulation. As you can see in the picture, they insulated everything above ground level. Currently, the temperature is fine down there, probably in mid 60's when it's been -10 outside and that is with the air duct closed for the basement. With that, I don't really feel as if we need additional insulation between the new studs, just pop up new walls and start drywalling. But, I could be missing something obvious so that's why I'm asking here. Any reason to insulate if the temp is fine as is?

Thanks

 

[Bretny]

I would prob insulate no matter how warm it feels. Whats the wall/floor temp when its that cold out?

 

[engineer2]

I agree, definitely insulate. I've been in nicely remodeled basements that are chilly in the winter because the homeowner didn't spring for a couple of hundred in insulation. Do it once, do it right.

If there is any chance that you could ever have water in the basement due to a failed sump pump, insulate the lower 18-24" with styrofoam and use greenboard for the lower course of drywall.

 

[4Kings]

You're going to want a vapor barrier over that concrete before you put up any stud walls. You'll be asking for mold issues if you don't.

 

[jconnor3]

You're going to want a vapor barrier over that concrete before you put up any stud walls. You'll be asking for mold issues if you don't.

A vapor barrier over the lower half of the wall or over the insulation too? How would you attach it to the floor if you didn't attach it to the back-side of the studs?

 

[Done That]

I think I'm going to try InSoFast panels on the area of my basement that is still unfinished. I did about half my basement 10 years ago with traditional framed walls.

A bit spendy, but it's rigid foam insulation with integral electrical raceways and "studs" to attached the drywall directly to. I think I'll come out ahead when time to put up stud walls, vapor barrier, insulation etc is considered.

I didn't know this kind of approach existed, so just throwing it out there for consideration.

 

[ford33]

I have a finished basement similar to your current construction. Things I learned over 20 years...

1. Insulate the basement wall from floor to ceiling. Use a rigid foam board insulation at the lower 1/3 so when, not if, you get water in the basement the foam can be dried and reused. Also use green board on the lower 1/3. Stainless fasteners on the lower wall would also be good.

2. Insulate the space between the first floor above and the sill. This is a cold spot in my basement and difficult to fix once the drywall is installed.

3. Add water shut-off valves in an accessible location near the outdoor spigots. You want to be able to replace the spigot without shutting water off to the house. Also, should the pipe freeze you can shut off water to just that supply line.

4. Make the ceiling accessible. I have added electrical lines, lights, water lines over 20 years and having a removable ceiling makes it so much easier. Check and seal tightly any wall openings to outside. Little critters will like your nice warm basement in the winter and will dig their way inside.

5. Consider vinyl or tile flooring with a heated floor. Basement floors get cold and uncomfortable. Skip the carpet in the basement. Once you get water in the basement, and you will, the carpet and pad are ruined. It is a huge mess to clean that up and toss the carpet.

6. Install a very good sump pump system and a very good backup system. And maintain it every year. I have three pumps in my well now. That is one more from about 5 years ago. You need to provide entirely separate outlets for each pump. If all pumps go through one pipe you have a single point of failure. If the pipe freezes or clogs, the pumps do not work.

7. Consider how you will access the electrical, water and heating system once the basement is finished. Make it easy to maintain these systems.

 

[4Kings]

For your floors you really need to consider a subfloor. Many ways to do it. I used Dricore panels, a bit spendy but well worth IMO.

http://dricore.com/nw/rplus_about.php

 

[C_F]

For your floors you really need to consider a subfloor. Many ways to do it. I used Dricore panels, a bit spendy but well worth IMO.

http://dricore.com/nw/rplus_about.php

That's a very interesting product they have, thanks for posting the link.

 

[Showkey]

I hav done a few basements over the years........the last two I painted the walls with “basement water proofing paint product” before studs and insulation. Alittle over kill but dramaticly redudes the moisure moving through the walls. Same on floor before carpet......seal as much as practical.

Also used high quality carpet square product.........have a problem.......it’s real easy replace or dry out when the leak or small flood happens. One ocurance ........ten inches for rain in one day.........window wells filled up and leaked in. 20 tiles got wet.........pulled up in minutes, dried and put back down days later.

 

[ItsNemo]

Up here in the snowy white north, we typically stud floor to ceiling just in front of the foundation walls (leave a 1/2" air space)...sill gasket or poly under the bottom plate. Insulate between the studs and then 6 mil vapor barrier over it all.

Keep in mind that basements here are built with exterior waterproofing (membrane, dimple board, etc), so water is rarely an issue.

 

[The Cobbler]

You're going to want a vapor barrier over that concrete before you put up any stud walls. You'll be asking for mold issues if you don't.

I disagree. vapour barrier should be on the heated side of the insulation.
tar-paper or tyvek allows breathing and wont trap moisture on the cold side of the insulation like vapour barrier will

 

[engineer2]

ford33

Spoken like a true Chicagoan. That's exactly how I've done basements. Floor heat is the best.

 

[Bretny]

Make sure you use PT wood every where wood touches concrete.

 

[polizei1]

Up here in the snowy white north, we typically stud floor to ceiling just in front of the foundation walls (leave a 1/2" air space)...sill gasket or poly under the bottom plate. Insulate between the studs and then 6 mil vapor barrier over it all.

Keep in mind that basements here are built with exterior waterproofing (membrane, dimple board, etc), so water is rarely an issue.

Same here, this is how I would do it.

 

[jconnor3]

Up here in the snowy white north, we typically stud floor to ceiling just in front of the foundation walls (leave a 1/2" air space)...sill gasket or poly under the bottom plate. Insulate between the studs and then 6 mil vapor barrier over it all.

Keep in mind that basements here are built with exterior waterproofing (membrane, dimple board, etc), so water is rarely an issue.

Yea, this is how I was thinking as well now that I'm looking into it more.

My thing was that I wasn't sure if insulating between studs would just be redundant since there is already insulation for anything above ground level and the temperature is good, but I guess additional insulation couldn't hurt.

 

[LX-Markham]

This is the wall system we are going with this summer when we do the basement.

The solid/continuous layer of XPS acts as the vapour barrier. Wood studs are not in contact with the concrete wall. We are going with 2" XPS against the wall, and 1 1/2" XPS between the studs. Total thickness (with drywall) 4". Total R value 18.

Avoid using batt insulation.

 

[Steevo]

Up here in the snowy white north, we typically stud floor to ceiling just in front of the foundation walls (leave a 1/2" air space)...sill gasket or poly under the bottom plate. Insulate between the studs and then 6 mil vapor barrier over it all.

Keep in mind that basements here are built with exterior waterproofing (membrane, dimple board, etc), so water is rarely an issue.

This is exactly how it's done here in Idaho as well.

 

[firebirdparts]

You're going to want a vapor barrier over that concrete before you put up any stud walls. You'll be asking for mold issues if you don't.

In my basement this would cause mold to grow furiously between the block and the barrier.

 

[jdieter]

Did this to our walkout basement a couple years back in northern Indiana. Basement has never been wet in 20+ years, house is on a hill side with perimeter drain. Covered floor with 3/4 rigid insulation, spray foamed and taped all seams, then added 3/4" T&G plywood subfloor, metal studs 1" off concrete walls and 4" closed cell spray foam all way up to rim boards. Dry-walled ceiling and walls.

 

[4Kings]

This is the wall system we are going with this summer when we do the basement.

The solid/continuous layer of XPS acts as the vapour barrier. Wood studs are not in contact with the concrete wall. We are going with 2" XPS against the wall, and 1 1/2" XPS between the studs. Total thickness (with drywall) 4". Total R value 18.

Avoid using batt insulation.

This is exactly what I meant when I mentioned vapor barrier in my earlier post

 

[hand]

It is worth a good look at the Building Science Corporation (BSC) guidance on basement insulation:

https://buildingscience.com/documents/information-sheets/basement-insulation

Bottom line is that foam board is much preferred over fiberglass for basement applications.

Insulation both keeps the basement warm in the winter and reduces condensation on the walls in the summer if done correctly.

 

[jconnor3]

If I used kraft faced insulation, that will be my vapor barrier.

My concern is that there is already insulation on half of the cement walls. I'm not sure what to do there since half of the cement wall is insulated, then there would be an air gap, then studs and more insulation. See my dilemma? It just seems like a weird sandwich and which why I was considering forgoing the insulation between the studs because like I said the temperature down there has been fine even in sub-zero weather.

 

[LX-Markham]

My concern is that there is already insulation on half of the cement walls.

Easy: remove it.

 

[The Cobbler]

I would vote for the remove whats there & do whatever framing etc you want. re use the insulation or not. you could always tear off the paper face and toss it in your attic for extra up there

 

[ItsNemo]

Easy: remove it.

This...take down that existing ****, it's an awful way of insulting and is done to save money so they don't have to stud things out or anything, they just nail it up and call it a day.

 

[Handyandy23]

If I used kraft faced insulation, that will be my vapor barrier.

My concern is that there is already insulation on half of the cement walls. I'm not sure what to do there since half of the cement wall is insulated, then there would be an air gap, then studs and more insulation. See my dilemma? It just seems like a weird sandwich and which why I was considering forgoing the insulation between the studs because like I said the temperature down there has been fine even in sub-zero weather.

I personally don't see the problem with the "weird sandwich". The tiny bit of insulation the builder put there (likely because they had to meet local building codes) doesn't have a high enough R-value to do much for you on it's own, but I also don't see why you would tear it off when you could just add to it with more between the studs.

Like @Nemo said, in my basement and anywhere else I've seen in Canada, you just frame your wall with a small air gap to the crappy "builder" layer of insulation, put in your own batt insulation between the studs (with an appropriate R-value), then vapor barrier and drywall. It's really an easy way to do it, you know you have good insulation, and you're only losing a few inches off the whole space.

I've seen a few ways to deal with the floor / sill plate, but I just used the blue/green "treated" 2x4's for the base of the wall. I also used a product called DMX 1-step on the floor that comes in a big roll, and gives an air space under your floor to reduce the cold coming through, and in case you get any water.

Also as others have suggested it's a good idea to insulate (at least with something like Roxul Safe N Sound) in the ceiling so you don't get a cold pocket, and it also helps with noise transmission. When it comes to things like insulation in a basement, I'd tend towards overkill versus saving a few bucks. Depending how big the space is, it's only going to cost a few hundred to insulate really well yourself, and once you drywall and finish it you're not going to want to tear it back open again. Do it well once and don't worry about it again.

 

[ItsNemo]

I personally don't see the problem with the "weird sandwich". The tiny bit of insulation the builder put there (likely because they had to meet local building codes) doesn't have a high enough R-value to do much for you on it's own, but I also don't see why you would tear it off when you could just add to it with more between the studs.

Like @Nemo said, in my basement and anywhere else I've seen in Canada, you just frame your wall with a small air gap to the crappy "builder" layer of insulation, put in your own batt insulation between the studs (with an appropriate R-value), then vapor barrier and drywall. It's really an easy way to do it, you know you have good insulation, and you're only losing a few inches off the whole space.

I've seen a few ways to deal with the floor / sill plate, but I just used the blue/green "treated" 2x4's for the base of the wall. I also used a product called DMX 1-step on the floor that comes in a big roll, and gives an air space under your floor to reduce the cold coming through, and in case you get any water.

Also as others have suggested it's a good idea to insulate (at least with something like Roxul Safe N Sound) in the ceiling so you don't get a cold pocket, and it also helps with noise transmission. When it comes to things like insulation in a basement, I'd tend towards overkill versus saving a few bucks. Depending how big the space is, it's only going to cost a few hundred to insulate really well yourself, and once you drywall and finish it you're not going to want to tear it back open again. Do it well once and don't worry about it again.

Two things:

- Anyone half decent removes the builder **** and then frames in front. You're giving up square footage by having to bump the wall out further and shouldn't have the blanket stuff with it's own vapor barrier and then another vapor barrier in front.

- You shouldn't use pressure treated indoors and the blue stuff is not sufficient. Sill gasket or poly under an untreated or blue wood bottom plate is the correct procedure.

 

[rburke65]

When Finishing off a basement, the only type if ceiling I would ever install, would be a T bar ceiling with the lift out tiles. Trust me, you'll thank me later.