Finishing the basement

[Photon]

Furring strips are typically applied directly to a concrete wall in a verticle direction with the 2 (1.5) inch dimension flat to the wall, 16 on center. They are there pretending to be 2x4's for you to hang your drywall. Becuase the cement wall is structural, the furring strips are just screw acceptors. You would put your foam boards in between the furring strips for a total of roughly 3/4 inch of insulation.

This is the way it has been done for years, but this method leaves lots of uninsulated areas and lots of gaps to caulk. The Building Science Corp info makes it clear the insulation must form a continuous layer over the concrete, and even specifies using caulking, metal foil tape, or mesh and mastic at the joints. They like to add a framed wall over the foam using either wood or steel studs. If you need to save space, Dow makes a Styrofoam product that has grooves for furring strips called Wallmate XPS

It seems to me the objective is to not only provide some R-value to keep the space warm, but to also keep any moisture-laden air from contacting the concrete walls and having the moisture condense. Meanwhile, any moisture entering through the concrete has to dry to the inside as Lou said. Our basement has 2" of foam (R-10) on the outside all the way down to the footings. The interior surface still gets pretty cool in our Wisconsin winters, especially toward the top, so I feel the need to add some insulation on the inside before installing drywall. I've attached a polyethylene sheet to the wall to see if any moisture condenses on one side or the other, and it didn't. However, after the space is finished and we spend more time down there including sleeping, showering, cooking, and using exercise equipment, there will be much more moisture in the air. I'm likely to use either foam sheets or sprayed foam, then have a 2x4 stud wall over it. I think the sprayed foam would do a much better job in the joist cavities, but it costs more than twice as much as the sheet-foam method. The difference would buy a lot of caulk.

 

[beelzerob]

Meanwhile, any moisture entering through the concrete has to dry to the inside as Lou said.

Ya, I understand about keeping moist warm air inside the house from reaching the cold concrete...but how does any moisture in the concrete dry to the inside when we're putting foam right up against it, or sealing it with paint/sealer as some sites have suggested?

 

[Photon]

Meanwhile, any moisture entering through the concrete has to dry to the inside as Lou said.

Ya, I understand about keeping moist warm air inside the house from reaching the cold concrete...but how does any moisture in the concrete dry to the inside when we're putting foam right up against it, or sealing it with paint/sealer as some sites have suggested?

Well, as stated in the link I mentioned earlier, the foams don't completely block the moisture:

The best insulations to use are foam based and should allow the foundation wall assembly to dry inwards. The foam insulation layer should generally be vapor semi impermeable (greater than 0.1 perm), vapor semi permeable (greater than 1.0 perm) or vapor permeable (greater than 10 perm) (Lstiburek, 2004). The greater the permeance the greater the inward drying and therefore the lower the risk of excessive moisture accumulation.​

Regarding the paint/sealer issue, I don't understand the fine points. I would guess the sealers would slow or prevent the movement of moisture horizontally to the inside space. If the amount of moisture within the concrete increases, then I guess it would pass more moisture through the top of the wall into the rim joist spaces and down through the crack between the footing and the bottom of the wall where it has an easy shot into the inside space. If the wall develops cracks or other defects over time, moisture will have another escape route to the interior. With a finished wall covering/hiding what is happening on the face of the concrete wall, we probably won't know what is going on until we smell or see mold.

I claim no expertise in the area of basement insulation and moisture control. I don't own stock in Building Science Corp. I trust what they have to say because it makes sense to me and because they are partners in the US Department of Energy's Building America program. DOE Building America

Our house is a bit different than most of the situations I've found on the web in that we have a walkout basement. The entire East wall of the basement is frame construction. My project to finish about half the basement area will use most of this East wall and just 20' of the concrete North wall. The rest will be simple partition walls with unfinished basement on the other side. One scenario Building Science describes is in the Summer when it is rather humid, but nice and cool in the basement area. If that humid air can contact the cool concrete wall, then it might drop below the dewpoint and condense. If the wall surface is sealed, the water will have little chance to leave. Since we have eleven windows and a patio door down there, it seems to me there is an excellent chance that we will eventually fill the basement with very humid air. I will be able to see all the concrete foundation wall except for those 20 feet; however, anything hidden inside that 20 foot section could be very expensive, especially since part of it is the bathroom wall.

 

[beelzerob]

Man, this gets exasperating quick.... On the one hand, it seems like you should seal the air from inside the house from getting to the concrete wall, because then it might condense. On the other hand, if you seal it, then you're trapping any water that gets through the concrete into that area.



That's a good point about the concrete cracks. What good sealing the concrete if (when) it develops a crack.

I appreciate the input and thoughts Photon, and I know you're not pushing any info for a particular agenda or gain.

It seems like the way to quickest get into trouble is to use a vapor barrier (plastic sheet) of some kind. I mean, right now, without touching my wall, I'm perfectly fine!! But as soon as I want to put stuff near it, I'm getting in trouble. I know I could put up pressure treated studs right against it and have a wall I can hang plywood on and build shelves on, and I'm guessing I wouldn't have any issues from that, because again, it's really no different than what I have now, and moisture might get to the wall, but it wouldn't be trapped there. If water condenses on the wall, that would be bad...but it's not a scenario I've seen (except for that mysterious water on the floor that one time). I'm already having to run a dehumidifier to keep the moisture level in the basement down. I had heard that putting up insulation would reduce the amount of overall moisture in the air down there. That, and it'd be nice if the workshop was at least a *little* bit warmer in the winter. I'd expect to have a space heater down there in any case for when I'm working extendedly (I've spent hours down in the wiring room taking care of stuff...a light jacket and some coffee, and I was fine).

I really didn't like the idea of having to cut the foam sheets to fit inbetween studs, just due to gaps and irregular shapes....so I'm ok with losing some space to have continuous foam panels (and taped) and then placing the wall studs on *this* side. And I think the building sciences shows doing that, complete with fiberglass insulation in between the studs (don't know if I'll do that or not...probably overkill for a low use area). But I don't recall seeing in the diagrams them putting up a "vapor barrier". It seemed like just the foam panels and then 2X4 studs up against that.

 

[Photon]

". . . (except for that mysterious water on the floor that one time). "

Yea, I've been meaning to comment on that, too. Was the puddle in an area you intend to finish? If so, I'd be doing more detective work there. Murphy's Law says it will do it again after you spend the big bucks to finish the space. I've twice in three years here had a puddle just inside my framed basement wall, and in both cases it was after rain with severe winds. I eventually found it was entering around the dryer vent, which I fixed with flashing and caulk. I could see water running down the vapor barrier, and when I pulled the poly film down, I found the fiberglass batts saturated in that area. I was REALLY pleased I hadn't finished off that space with drywall, wood floor, etc.

One detail I'm taking care of while I can still access the bottom of the main floor and the unfinished framed wall in the basement is to run cable for the security, LAN, video, and audio systems. I had the builder install empty electric boxes in the exterior walls of six main floor rooms with empty smurf tube running down into the basement. I am in the process of extending several of these across the basement with rigid PVC conduit into areas that won't be finished space. I'm also agonizing over whether I want to wire for water leak sensors in the kitchen and one bath as well as PIRs and glass breaks in a couple other rooms where I'll lose access when the basement ceiling drywall goes in. I'm tempted to use a suspended ceiling in the basement to maintain access to the bottom of all the upstairs walls, but I really hate suspended ceilings. I encourage you to think about these sorts of things when you get frustrated over the vapor barrier/insulation issues. I find it helps keep my blood pressure down.

 

[apostolakisl]

I would focus on sealing the wall with an applied paint like substance. This prevents ground water from weaping through the wall and into your basement. These products work well if you aren't talking about serious quantities of water. It won't trap moisture, water that is in the wall can still escape to outside and moisture on the inside can still escape to the room. I would use no vapor barier in your wall construction. Doing that could trap moisture in a place mold could form. If the wall cracks, you are hosed no matter what and have an expensive repair. Nothing you would do to finish your basement wall would make it ok to have a crack.

I think pressure treated wood is pretty silly. If you have enough moisture to damage regular wood, then you have enough moisture to ruin inulation, drywall, carpet, etc. and you shouldn't even bother.

Applying furring strips directly to the wall is a fine solution if you aren't needing a high r-value. Furring strips are wood and wood is a pretty good insulator. You are just only getting about 3/4 inch of it. That is how the basement was done in the house I grew up in. We lived in an area with sandy soil, had no sump pump, and never in 25 years had a drop of water in our basement nor did it smell or have any issues at all in that respect. This was in Toledo, Ohio and the basement was very comfortable with just a regular old dehumidifier. It was ventilated on the same HVAC system as the rest of the house.

I really doubt you will get condensation forming on your walls with a dehumidifier running in the basement. Your walls would have to be pretty cold or your humidity pretty high for that to happen.

The most likely water issue is going to be ground/rain water getting in and is way way more likely than any condensation problems from humid inside air. I really would focus on that problem and put up as many r's of insulation as you think you need with your ground (and thus basement wall) temp.

 

[beelzerob]

Yea, I've been meaning to comment on that, too. Was the puddle in an area you intend to finish?

No, it's on the opposite side. The only thing I can *possibly* think it is (other than condensation, because the humidity WAS quite high in there) is the drainage is poorest along that wall on the outside. The last half foot or so of ground slopes towards the house instead of away. Im not happy about that but I haven't found a good solution yet...the rest of the yard is already almost up to the siding, so adding dirt there will bring it up too high. Still trying to figure out that one....

Anyway, that was the only place we've found water like that, and even though we've not fixed the ground issue, we've never seen it again, so it's just as likely to have been condensation.

Even the term "finish" might be stretching it here. All I *really* want is a complete wall for storage. But while I'm doing that, I might as well add some insulation if it will mean a more comfortable room in the winter. The only wall I'm bothering with insulation though is the part of the workshop along the outer wall. So, the room won't be finished by any stretch. I forsee putting 5/8s plywood on all surfaces, but that'd be about it.

 

[Photon]

At our last house the back yard sloped toward the house from about 10 feet out. I couldn't change the contour of the yard for a number of reasons, so I dug a trench about 18" deep parallel with the foundation which I pitched toward the side yard, lined it with landscape fabric, laid a perforated 3" drain pipe, and filled the trench with gravel. The back foundatin wall was usually damp after a good rain or the Spring snow melt before I did the drainage ditch, but it was pretty dry after that. The dehumidifier didn't run nearly as much either.

 

[beelzerob]

Ya, I've considered many options, but this particular area is bordered by our garage on one side and our front porch on the other. We have a french drain of course, but I'd rather not have any ground near the house sloped towards it.

Really, our only option that I see is to have an excavator come in and regrade the land from around the house out. All it would really mean is $$ and loss of our front lawn...but that's not a heavy price. Our front lawn is simply there because mud would be ugly. It serves no other real purpose.

 

[drozwood90]

Ok, so we think we've settled on the area that is the workshop and theater area in the first floorplan as being the current workshop. It loves lots of room for the kids to ride their bikes around, and leaves a small little area outside the wiring room for storage (as well as under the stairs still).

So that gives a workshop area about 40' long and going from 10' to 12' wide. Kinda narrow, but lots of room for long boards.

Next up is deciding whether we're going to insulate and put walls up along the outer concrete wall. I'm not sure how much insulation would matter to the overall comfort of the room...I'm sure I'll have a space heater either way. I'm mainly thinking about having a place to hang stuff, but I could just use tapcon whereever I need to attach 2X4 to the wall.

Does anyone have any experience with building an enclosed area in the basement like this, in regards to if insulating is a good idea? I've been told the 2 main options are to use the blue foam and glue it to the wall, or to use 2X4's and fiberglass insulation, but offset with a 2X6 top rail and bottom rail so there's an air gap.

Probably late to the party, but having a thicker pad on the floor and some insulation on the walls turned my last home's Basement Theater from a "cold-clammy" feeling, into a nice warm room that the whole family wanted to hang out in.

I think the LARGEST influence was the thicker pad on the floor (or put in some kind of floating floor that has an air gap for insulation). Home Depot had 2'x2' squares with lifters on the bottom, to make a floating floor. Personally for the $$, I went with thicker pad.

Oh, and painted the walls and floor with concrete sealant paint, then put up the walls and flooring down.

--Dan

 

[drozwood90]

What kind of compressor do you guys have? My large oilless Husky died last fall, and I need to pick a new unit, but can't figure out what to go with.

Just had my wife dig out the paperwork to my latest compressor.
Its a Sears model No. 919.167620 Perm Lube Single Stage, Portable.
33 gallon tank - mine is verticle, but they sell (sold) the same model in a horizontal config.
150 PSI
SCFM @ 40 6.3
SCFM @ 90 4.9

I keep the working pressure not far below 90. Very nice recovery time and possibly overkill for your app. I have multiple lines attached and have used 3/8 & 1/2 inch air tools simultaneously (2 mechanics working) for extended periods of time - Not little nailer tools, mind you - talking about larger cfm mechanic tools. Will run continous - but keeps up.

For what I've thrown at it thus far, I've been pleased. This style compressor is a single piston design and I can see it wearing out in a few years if you gave it hard daily use in a real "shop" environment - I expect mine will last the full 10.

It was inexpensive + then a sale 2 weeks after my purchase brought the price down to 175.00 or so. Less thn a year old.

I've got the same one. Works really well.

 

[beelzerob]

Probably late to the party, but having a thicker pad on the floor and some insulation on the walls turned my last home's Basement Theater from a "cold-clammy" feeling, into a nice warm room that the whole family wanted to hang out in.
--Dan

Nonsense, any input is good, and I haven't moved much closer to implementing any of them. Good suggestions all, though I think a thick pad and carpet might seem a little out of place in my workshop.

 

[drozwood90]

Yea, I've been meaning to comment on that, too. Was the puddle in an area you intend to finish?

No, it's on the opposite side. The only thing I can *possibly* think it is (other than condensation, because the humidity WAS quite high in there) is the drainage is poorest along that wall on the outside. The last half foot or so of ground slopes towards the house instead of away. Im not happy about that but I haven't found a good solution yet...the rest of the yard is already almost up to the siding, so adding dirt there will bring it up too high. Still trying to figure out that one....

Anyway, that was the only place we've found water like that, and even though we've not fixed the ground issue, we've never seen it again, so it's just as likely to have been condensation.

Even the term "finish" might be stretching it here. All I *really* want is a complete wall for storage. But while I'm doing that, I might as well add some insulation if it will mean a more comfortable room in the winter. The only wall I'm bothering with insulation though is the part of the workshop along the outer wall. So, the room won't be finished by any stretch. I forsee putting 5/8s plywood on all surfaces, but that'd be about it.

Can you back fill that area? If not...

Can you french trench away from the house in that area?

I had some strange "flooding" in my last house.

I installed 2 sumps and a WHOLE HOUSE surrounding french trench. I hooked in all the gutters and surrounded the entire house. It really worked! After all that, there wasn't any water in the house.

--Dan

 

[Neurorad]

I have a floating laminate floor in my workshop. Makes it more comfortable, with a pad underneath, but I don't think it matters. Wife really wanted a finished room, so my workshop could be repurposed if we ever move. I plan on scratching the heck out of it, so I doubt it will be usable for another purpose after we move.

You should consider having a dedicated HVAC intake from the workshop, if you do much wordworking, to keep the dust from blowing into other rooms in the basement. Right now, I have a single intake from the entire basement, in the kids playroom. I haven't done much to make dust, so it hasn't been an issue - yet. When I get a table saw, I'll prob get a dedicated return for the room. It will certainly be down the road for you, since you're not closing in the room yet.

I think open studs in a workshop would be fine, for the near future, if you only need to hang stuff on the wall.

I'm eager for you to move into a discussion of lighting options, so I can learn from your mistakes.

Line voltage wiring will be another consideration - outlets in ceiling for power tools and air filter, 220V for saw/dust collector. I guess I should wait until you bring those items up, in your thread.

 

[drozwood90]

Nonsense, any input is good, and I haven't moved much closer to implementing any of them. Good suggestions all, though I think a thick pad and carpet might seem a little out of place in my workshop.

Not really. This is what I put in my workshop area down in the basement:
well, I couldn't find the actual product, but I found a picture of the actual thing.
http://www.harborfreight.com/media/catalog...635_zzz_130.jpg

I also got it on a REALLY good deal. It was on sale at Harbor Freight for $9.99 each, and I had a 25% off coupon (for my entire order). So, I bought enough to cover the entire bottom floor. This is what I used for my pad. The wife and I put them down, then put throw rugs over it. Worked REALLY well. REALLY warmed up the place.

--Dan