Finishing Basement: Fastening Exterior Walls to Floor

[kevharper]

I'm finishing my basement. I've read many previous posts about fastening walls to the floor. But my question is a little different....

Many of the walls I'm putting up (traditional 2x4 construciton frames) are right up against the poured concrete exterior walls of the basement. What type of fastening for the lower wall plates is acceptible for the walls that butt up directly to the exterior walls? I was thinking just a little Liquid Nails would be OK for the exterior walls since any force that may be applied to the wall would just be absorbed by the poured concrete walls of my basement behind them.

For the interior partition walls, I was going to use nails fired through the plates and into the concrete of the floor with one of the .22 calibre nailers and some Liquid Nails (for a little insurance & to hold the plate in place during nailing). I'm using PT wood & galvanized nails for the lower wall plates.

Thoughts or suggestions? Any suggestions regarding sealing?

Any issues with floors cracking from the nailing?

Thanks, Kevin

[Art]

I believe you are supposed to leave a gap between the wall studs and the concrete unless you enjoy moisture problems.

[Joey]

Kevin,

Personally I would drill into the concrete and use an appropriate anchor. They make some new types you might not be aware of. One is inserted into the hole and hammered until it spreads. Then a nut is screwed down on it. They even make concrete screws/anchors but I haven't had good luck with those. The liquid nail would probably seal the underside but cheaper caulking would do the same.

J

[e-mail] wrote:

[kevharper]

How much of a gap do you suggest? the 1.5" of a 2x4 would be convenient to do. I have not heard about this technique to help reduce moisture problems. Anyone have experience with that?

Thanks for your replies everyone.

Kevin

[Goedjn]

Just enough to put or spray up a continuous layer of closed-cell foam.

[bambam]

Leave a gap of a half inch or more. Think of it as breathing space.

Just shoot em in using a Hilti or a Ramset. 2 1/2 nails, yellow charges.

Overkill. See above.

Naturally you will be insulating and installing vapour barrier.

Insulation is R20 above ground, R12 below ground. Vapour barrier goes on the WARM side of the insulation.

Ken

[kevharper]

Thanks all.

I have the green charges right now. If they don't work for me I'll be picking up the yellows which I think have a little more kick to 'em.

Yes I'm definitely insulating and planned on a vapor barrier on the warm side.

So I have a suggestion for a gap and one for using spray-on closed foam. I like the gap idea as opposed to the closed foam since it doesn't add cost. Is there a big advantage to using the foam over a gap?

Thanks again ALL!

Kevin

[Jeff]

I just used standard 22 nail gun. My 14 year old son loved firing it although often he didn't swing the hammer hard enough. I had to leave a little space in back as the floor was not even next to the walls. Never had any of the walls shift. I put up paneling and did a lot of driving of nails into the walls.

I also painted the walls with water sealing plaster (Bil Dry, I believe) before doing anything.

I found it was worth the trouble to predrill the bottom plate as it was hard to drive galvanized nails through the pressure treated wood mainly because the studs weren't against anything.

[Calvin Henry-Cotnam]

Lately, I have been going with Tapcon concrete screws, about one every

16-24".

By "directly to exterior walls", you should leave a small space - partly for breathing space to avoid moisture problems, and partly because that exterior wall may not be as plumb as you will want your stud wall to be.

A good practice to follow. I go a little further (yea, "overkill") and also use sill gasket between the PT plate and the concrete.

Our building code requires that sill plates be either PT or use sill gasket beneath them, and when we built our home we went with both, so I follow the same practice anywhere a wood is fastened to concrete that is on ground.

[kevharper]

Thanks for all the feedback guys. You've given me a lot of feedback that I definitely do apprecaite. I will definitly make sure I have an airgap between my stud wall and the concrete to have decent ventilation back that and to make sure my walls are nice and plumb.

Thanks again for all your feedback and if anyone has any more suggestions, please let me know!

Kevin

[kevharper]

Is there any benefit to putting vapor barrier on BOTH sides of the wall that is against the basement wall? Or would that actually create a moisture problem?

[Tony Hwang]

Hi, Are you sure you can do that? Is your walls 100% plumb? Go easy on it. Also frame height better be little less than ceiling height and let the wall float. Concrete nail with a gun(rent one) will work well.

[Martin]

I'm not criticizing the suggestions but just thinking that I would have had some fun if those nailing guns were available at the time, but when I finished our basement 40 years ago I just used 2x4 sole plates fastened to the concrete with cut nails banged in with a old fashioned hammer and elbow grease. Painted the plates with copper chromate and toe-nailed the studs to it and to the joists above. Kept the studs about 1/4" from the foundation wall and covered the framing with prefinished paneling using a liquid nails type glue. Put in a dropped ceiling with flush lighting. Still in great shape despite many periods of high moisture.

[Jim Redelfs]

I have seen two very disparate methods of finishing a basement/below-grade wall: Furring "strips", half-studs or full, "2x4" studs *or* 4x8 sheets of high density polystyrene (StyroFoam) glued (PL400?) to the concrete wall (poured or block) and sheetrock glued to that.

Which is better? Which is more "do-able" by a do-it-yourselfer?

[Doug Miller]

Tapcon fasteners and a hammer drill.

[Doug Boulter]

[e-mail] wrote on 31 Mar 2006:

Let me add some perspective here. It will make a BIG difference how long the concrete floor has been in place. If it's been curing for 40 years, it will be a bear to shoot the nails into or to drill for tapcons.

My floor was so hard that I used the highest load, shot a nail into it, pulled the nail with a crowbar, and then shot a second nail in the same spot. And that's AFTER drilling the PT plate.

For all your walls, I'd use a combination of adhesive (there are better alternatives to Liquid Nails) and shot nails. If the concrete is relatively new, I'd use tapcons and adhesive.

[dss]

Kevin,

Code in my part of Minnesota now calls for a moisture barrier between the insulation and the exterior wall. This is in addition to the traditional moisture barrier between the insulation and the interior wall. This is also the case in much of Canada.

You can just staple plastic sheeting to the studs.

It wouldn't hurt to see what your local code requires. (Even if you aren't pulling permits.) My city has some of the more common requirements on-line and the inspectors are usually pretty helpful.

dss

[Terry]

Don't know for sure but you may have good idea. Look at a the site operated by 'Shell Busey'.

Search his site for "Basement Finishing".

You should get an article that describes putting 10 foot wide plastic sheet down the concrete wall, under the stud wall**, then putting the tail-end up the inside of the wall, overlapping that with the actual vapour barrier on the inside (warm side of the wall under the plasterboard or whatever), the vapour barrier then going up to the ceiling etc, see his diagram.

The reason given is "to prevent moisture emanating from the concrete to the wood studs". I like that idea; although I have no problems with dampness it sounds like a good idea. It encases the stud wall where it is below grade/ground level with plastic on both sides; might be good idea, at the top of the wall outside the new basement stud wall there will be an air pocket that can breathe to the outside?

** hadn't realized this before but Busey also shows the bottom plate of the proposed basement stud wall sitting on a pad of foam insulation, same width as the 2 by 4 plate! Thus insulating it from the concrete floor??? I guess the foam will stand the weight of the wall? Most of us would put a piece of PT treated 2 by 4 as the plate w/o foam and then use regular studs, I think?

Idea anyway. Terry

[Art]

My basement was finished 9 years ago with a gap and have had no problems. But it also has a functioning french drain system inside and out. It is heated and air conditioned.

[kevharper]

Terry- Thanks a lot for the link. Looks like good info.

I guess if I go with NO air gap but have the plastic sheet on both sides of the stud wall, that will protect the studs from any moisture emanating from the wall. Also, having little or no air gap will reduce the amount of moist air from the house to get between the stud wall and the concrete wall.

But it also seems having an air gap would help to ventilate any moisture that may tend to collect between the fram system and the wall.

It seems the best of both worlds is the plastic sheet both sides of the wall to protect both the wood and insulation and then leave some air gap to allow some ventilation?

BTW. I'm in SE Michigan. It doesn't reallly get that cold here and I don't plan on heating or air conditioning the basement. I will mainly use the basement to entertain in the Summer, Spring or Fall. Occasionally in the Winter. It will always be nice and cool down there but never cold enough to warrant any extra heating than what I get from heating the rest of my ranch. Also, I run a dehumidifier just to be safe....

Thanks again for everybody's feedback. If anybody has any more I'd love to hear it!

Kevin