Finishing Basement - best way to DIY waterproof

[Woodchuck34]

We just bought a new house, almost the day after I finished my current basement. Go figure. I'm a regular on rec.woodworking, but thought this question would be better applied here.

We had a local engineer do our house inspection and he has an excellent reputation. He outlined the best way for us to finish the basement. First, a little background. Its poured concrete, built in '92, and doesn't appear to have any leaks, doesn't even have a sump pump, but I want to make sure I don't have any moldy or musty smells after I finished.

This engineer recommend that we glue a 6 mill vapor barrier 8" below the sill plate on the walls, keep the stud frame 2" off the walls, and bring that barrier down and around the floor plate on the new stud walls. Also recommend using some sort of waterproofing sealer/paint.

First, has anyone ever heard of glueing the barrier directly onto the wall?

Second, what is the best sealer to use?

I live in PA for climate reference.

Any help or suggestions would be much appreciated. I'll paste the relevent parts of the report below.

Thanks,

Chuck

For your reference we are providing the following general information regarding finishing the basement into living space.

First seal the interior of the basement foundation walls and floor with a good quality waterproofing material. Both surfaces should receive at least two coats of the sealant. Deco, UGL Drylock and Glidden make commercially available products for this purpose. There are also other available products as well as some commercial grade products available through certified installers that should be considered.

Following this, a 6-mill or thicker polyethylene vapor barrier should be attached to the top of the foundation wall approximately 8 inches below the sill plate. This polyethylene should be glued and bonded to the foundation wall with appropriate adhesive. It is important to obtain a good seal in this regard to prevent moisture from migrating upward to the wood sill plate around the perimeter of the foundation. The lower end of the vapor barrier should be placed under a new

2"x4" wood stud wall used to frame the finished basement area. Provision should be made to ventilate this space and allow any condensation that may develop to escape. The new stud wall should be attached to the first floor framing and the basement floor and should be located approximately 2" off the interior of the basement foundation wall. The vapor barrier should be as continuous as possible to prevent moisture from migrating into the wall or first floor framing above. The 2" spacing from the foundation wall will allow air to circulate in this area and reduce moisture levels. The interior frame walls can then be insulated and finished with drywall and/or paneling as is typically done. A dehumidifier or two should be used as needed.

[JoeSpareBedroom]

Before I'd do anything at all, I'd wait for a few days of rain, and use my nose to determine if there is, in fact, any dampness in the basement. Then, I'd spend some time outside figuring out the reasons. Sometimes, it's as simple as re-routing downspouts away from the house, or planting ground cover plants whose root systems slow the flow of water so the ground can absorb it more effectively.

[Banty]

Yes, that was done to my house by a previous occupant. And the basement partially finished with studs set back from wall, etc. as you describe. Also, a primitive cove trench along one wall was built leading to a sump pump.

There are still water problems occasionally which I will address by major re-grading and some drainage placed in a coupla years.

Live in the house for awhile, see what experience your neighbors have. Trying to stop water coming in by coating the *inside* of the basement walls is really not the best way to address it.

If you have clay soil and your neighbors report water problems, I'd even consider doing a BDry or similar system now while you have the wall still open.

Banty (I'm in upstate NY, by the way)

[Goedjn]

If you're circulating air behind the interior partition walls to keep moisture levels down, what's the point of insulating them? How are you driving air through there anyway? Vents at the base and top of the wall?

[No]

I would wait a year, see if you get water. If you don't, and its not too humid, I would just stud it out and be done with it. If you do get water then fix it from the outside.

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[Woodchuck34]

I have access to the house and have been able to work there to get things ready. The basement is dry except for one spot where a downspout is not moving the water away from the house properly. The engineer also thought the basement was sound except for this issue. I just don't want to go through all the work of finishing this, only to get a musty smell from the walls.

Has anyone used a sealer they can recommend?

I wasn't sure about this whole vapor barrier thing. I understand the concept of keeping the studs off the wall, but if you glue a plastic barrier to the wall, won't mold potentially still develop in between the plastic and the concrete?

[Joseph Meehan]

Woodchuck34 wrote: ...

I am going to go along with those who suggest waiting a while and see what happens . If you really have a problem, you will want to know about it before you do any refinishing. If you really have a problem, the only real fix is to attack it from the outside. You can't do it from the inside.

As for the question of high humidity, I suggest that serious ventilation should be considered first. During the winter you want additional moisture in most homes anyway, ventilate it from the basement.

[Art]

You need to make sure that you have an external system for drainage outside the basement. The inside stuff is secondary. Also if you have any sewage pipe in the basement, put in a one way valve. Most codes require it now for new construction. Also make sure homeowners insurance covers sewage from external source. It is usually a cheap option.

[Art]

I guarantee you that if you don't put in an outside drainage system, the basement will flood as soon as it is finished.

Studs only need to be 1/2 inch from wall.

[Paul Franklin]

If you actually have water coming through, you need to fix that from the outside; whatever is required.

If you just have water vapor diffusing through the wall, then the interior dampproofing can be very effective. I've had excellent results with the oil based Drylock. It smells horrible when you are applying it, but it does work well. The latex formula isn't nearly as effective.

Here's what I've done and it's worked well for me. After living through a rainy season to make sure there are no actual water leaks through the wall, I caulk the seam between the walls and slab with polyurethane caulk. Then I applied the oil-based drylock to the walls. Two coats, with a brush. You really can't roll the stuff on effectively, although you can roll it on and then brush it in. It has to fill all the pores in the block to be effective. Let it dry for a week or so, until the odor is completely gone.

Then I glue two inch foam insulation board to the wall, using the proper foam compatible construction adhesive. You need the solid cell foam that doesn't absorb water, and the type with borate treament to eliminate any chance of mold or insects is best. All the foam seams are taped with the type of long-lived tape used for house-wrap or equivilent. The object here is to form a very good vapor barrier so warm moist air from the inside doesn't reach the cold wall and condense. Tape the foam to the floor as well.

Then I build a 2 by wall 2" or so out from foam. It doesn't need to be insulated because of the foam, which makes it much easier for running utilities, etc.

This is not a cheap project, the drylock and foam are pricey. But it really works well, as long as you don't have any seepage anywhere through the wall before you start.

As always, clear all this with your building department. You may get stuck providing a means of secondary egress before they let you finish the walls at all.

YMMV. Good luck with your basement.

Paul

[ds549]

b dry did my basement wall for 1300.00 .they put in a trench and sump pump. i reccomend them.lucas

[hallerb]

Having lived thru the nightmare:(

Regrade outside install downspout drains well away from home and drain preferably to open air and if not a dry well system with overflow protection, make sure gutters are good, gutter helmet type save tons of hassles. helps keep gutters downspouts and drains clear

then just to make certain install interior drain system to a sump, preferably draining by gravity well away from home. Covering walls with plastic can be done but with a interior french drain its not necessary, just drylock the walls, add extra mold preventer to the drylock.

this is the ONLY WAY to be sure one day your nice room wouldnt be ruined.someday. its near impossible to properly install a interior french drain system into a finished basement. better to do now....

get tested for radon since its going to be a living area, and if theres even a remote chance of it being used as a bedroom add ingress egress windows.

you may wonder about the dry basement belt and suspenders approach. all it takes is a single abnormal rain to ruin a nice room. all preventable.

you could instead add a exterior french drain but be certain its BELOW the level of the footer.

theres nothing worse than doing a room twice:(

[Norminn]

I don't know anything about such a system, but what is not mentioned is of fair concern. Climate is one thing, local conditions and slope of property another. As for the system you describe, I would want the engineer to define the requirements for ventillating your wall system - how much air movement required, what equipment and what will that cost to operate. With what you describe it seems almost overkill for the walls and not much about the floor when the 100 year rains come. I would want to think about a sump pump for a finished basement, and water damage doesn't necessarilly come from the outside. What about a broken pipe?

The mention of moisture migrating upward to the sill plate puzzled me; concrete is never totally dry as I understand, so how wet could the sill plate get unless flooded?

Exterior drainiage is a major consideration in wet basements, so review of grade, soil and downspouts in order? Any discussion of waterproofing outside of basement wall, or has that been done?

[bambam]

.

There are two sources of moisture problems -- Most new homes "weep" a bit for a year or sp as the concrete cures. If yours is a new home, hold off for a year or so.

Or there is a break in the the building envelope and hydrostatic pressure is forcing ground water through the break.

Do you have a condesnsation or moisture problem? Tape a square of foil wrap to the floor and to a wall. Leave it alone for a couple of days. How much moisture did you get?

Problems from hydrostatic pressure can relate to the soil and the drainage .... high clay content, sloped toward the house, with gutters ending close to the walls ... is a sure recipe for disaster.

You fix weeping by waiting. You fix cracks from the outside. I do not know anyone who's solved a real problem by painting the walls.

Ken

[Jay Stootzmann]

Like everyone else said -- address your outside issues first -- that's where you'll get the most bang for the buck.

I used Drylock, oil based, 2 coats, when my basement was less than a year old.

I also sealed the floor with a good quality floor sealant.

Next, I would suggest then waiting a year or two to wait for the cracks to appear in the basement wall.

As you house ages you'll get a few hairline cracks in the basement walls. I filled all of those cracks with Drylock concrete calk and applied 2 coats over the cracks and 1 additional coat over the entire basement. [the larger cracks I also filled with an epoxy sealant.]

I run a high capacity dehumidifier [energyStar 70 pint] in the basement and another in my crawl space [EnergyStar 40 pint]. The basement is now quite comfy.

useful links:

[hallerb]

yeah painting the walls looks nice, but i have seen drylock bubble into a 12 inch diameter bubble filled with water, it broke.

so it does seal but it isnt perfect

Fix possible water problems in advance any buy fllod insurance just in case, if your basement room costs a lot

[Art]

Do not dig below your footers if you want your house to stay up in one piece.