Basement Insulation Question

[72Corvette]

We've just purchased house with a full basement. I plan on turning one end into a 18' x 36' wood shop. I've never had a basement before and the previous owner had done some work. I'm not sure about the existing insulation against the foundation wall. He ran a 2 x 4 stud wall flush against the concrete and stapled in batt insulation. From everything I'm reading the best option is foam board insulation. My question is can I leave the wood framing and just glue the foam board between the studs or should I pull the framing out and get an air gap between the wood and the walls. No sheetrock has been hung so everything is exposed at the moment.

Any info would be greatly appreciated.

Thanks,

Glen

 

[Elginz]

I would take it down and put up continuous foam board with construction adhesive and cover that with drywall using Tapcons. I know that works.

 

[James-W]

Some people build a stud wall with a treated 2X4 on the bottom. They build it slightly away from the concrete wall, then they have a spray foam company come in and do their thing. Once that gets done and the drywall has been put up, you have a really nice space.

 

[Crazyjake8493]

James-W's idea would be ideal, but probably more expensive depending on spray foam prices in your area. For DIY, I would put rigid foam (XPS) directly on the concrete wall with adhesive, then 1x3 strapping over that, screwed to the concrete. The drywall screwed to the strapping. Leave a gap between the drywall and floor, and PVC baseboard moulding.

 

[wyattoil]

I agree. Couple things I did differently was use 2x2's instead of 1"×3" - to fit electrical boxes and then cut 1.5" polystyrene rigid insulation board to fit between the 'studs'. We had the exterior walls/interior perimeter tiled to new sumps before we finished so hanging/attaching the 2x2's seemed like the best option to keep the metal drain tile base (? ) functional...and keep wood and drywall from touching the floor.

Interior Tile Base/drip catcher...?

2x2's attached to walls with tapcoms over .5" polystyrene

1.5" polystyrene between 2x2's with electrical outlets, metal clad cable on exterior walls, sound reducing plastic faced batt in the ceiling...and a cat box

Finished with drywall hung 1.5"+/- off floor, wood look tile and plastic moulding....just in case we get some water...though we have not had any since the interior drain tile was installed.

Sent from my SM-G900V using Tapatalk

 

[toyotadriver]

Don't use adhesive to secure the sheets to the concrete. Use canned spray foam to glue the sheets to the concrete. Works WAY better.

 

[jdieter]

Recently demo'd my basement with studs and batts. Basement has always been dry, but also had a musty smell unless I ran a humidifier 24/7 and it was chilly during the coldest part of our Indiana winter. Went with 3/4" rigid foam with 3/4 plywood on top for the floor and metal studs spaced off the walls one inch and then 3" spray foam and drywall. The foam encapsulated the studs making them very rigid. No musty smells, no humidifier and no chilly winter now.

 

[larry4406]

In new construction here in northern VA and MD, the company I work for offers finished basements.

When we do this, we frame 2x4 walls at 24" on center around the foundation interior and hold this 1" off the foundation wall to create an air gap. The sill can be pressure treated or regular (if regular, then a membrane is needed between it and the concrete floor, yes this is Code permissible). The top of the framed walls need to be fire stopped to the foundation (typically a piece of 3/4" subfloor plywood is used which is sandwiched between the wall's top plate and the joists above and runs over the foundation wall butting to the house sill plate. We then use Kraft faced R13 insulation in the stud cavities.

 

[Showkey]

Insulating the floor is very risky..........no matter how dry you think the basement it is, there's always the possibility for water intrusion. Water trapped under the floor is a BIG concern. ( ANY) Wood floor even on risers is a even bigger risk.

The intrusion may come from a pipe leaking, wash machine over flow, sudden 10" rain, sewer or septic backup, sump pump failure, power outage etc....... smart plan ......is to have a plan to get to bare concrete when bad things happen.

On the walls .......before wall building.... painting with "water proofing" paint is a very good start.

 

[RM209]

Depending on the type of foam board that you spec, you will see an increase in r-value for your basement. However, you'll have to determine whether the increased r-value is worth the cost over the already installed batts (probably R-13 if fiberglass in a wall framed with 2x4's) in which you essentially have a sunk cost of zero $. If you don't think the increased r-value is worth the expenses, you might consider carefully pulling back the insulation (and vapor barrier if installed) and caulking/spray foaming the sill plate area. It's amazing how much cold air (and moisture) can come in though the sills.

RM209

 

[DC73]

I would take it down and put up continuous foam board with construction adhesive and cover that with drywall using Tapcons. I know that works.

This might be acceptable but your climate is a cold one and the OP lives in Georgia. Georgia is a very hot and very humid. The OP must get the details correct. What works well in one climate may very well not be correct for another. For example, I live in a dry climate and we can use open cell foam under the roof deck here but you can't do that in cold or hot humid climates.

Any info would be greatly appreciated.

Do yourself a favor and visit BuildingScience.com and GreenBuildingAdvisor.com where you'll find plenty of information. The Q&A forum on GBA has building science gurus who can provide climate specific help.

Post a pic of the '72. You can see my '73 in my avatar.

Good luck,

DC

 

[FunBags]

I vote for spray foam, I did my whole basement and it was the best thing I've done to the house.

 

[jdieter]

Agree about foaming the sill area/floor joist cavities. Did that at the same time we foamed the basement walls.

 

[Jackfre]

I would paint the concrete basement walls with the UGH or similar paint prior to doing anything. In my previous home I pulled the "finished basement" walls down and etched & painted the concrete. It created a substantially dryer environment all on its own. I would feel greater confidence finishing the space as you intend with the painted walls.

 

[tjpavlov]

If you are starting over, check out "insofast" paneling. I'm doing my basement now and they are great.... especially for someone working alone.

 

[72Corvette]

Everyone,

I appreciate all of the info. I pulled down the studded section today and I'll get started on redoing it next weekend. I got lucky in that none of the other basement walls had anything done with them.

DC here's Ginger or as the wife calls her "the Other Woman". Other cars may come and go but they will bury me in this one.

 

[72Corvette]

Sorry I'm not sure why that wouldn't rotate correctly.

 

[72Corvette]

That's a beautiful 73. What engine option?

 

[DC73]

DC here's Ginger or as the wife calls her "the Other Woman". Other cars may come and go but they will bury me in this one.

Sweet. I was looking for a '72 when I came across my '73.

That's a beautiful 73. What engine option?

Small block. Not original. The original owner blew up the engine the first year he had the car. The block I have now is a replacement counter engine. The owner prior to me had it rebuilt to be the equivalent of the LT1 engines of that era. Puts out about 330 HP. It's fun.

DC