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gordonf238 04-22-2010 04:53 PM

Remodeling basement: Moist foundation
 
Hey guys. I've just joined the forums. I'm hoping to get advise on how to properly remodel my basement. I've received conflicting advice from various local contractors.

I'm a photographer, and need to finish the basement on my frame house (built 1930s) in Queens, NY in order to use the space for a studio. However, before I do that I need to address the moisture issue.

The foundation is lined with cinderblock, approximately 6-8" thick. and parts of it are consistently moist, moreso after rain, though there is no period at which the basement is completely dry.

Now, I've framed the entry to the basement with 2x4s and 5/8" greenboard (I try to learn as much about home improvement as I can as contractors in this area are very pricey). I was later informed that even greenboard will grow mold. I can already tell those parts of it that sit in the basement are already moist to the touch. So, be it as it may, I'm planning on re-framing the entry and using cement board, however, I first want to address the moisture issue.

One contractor had recommended that I use DRYLOK. So, to test how it works, I bought two buckets (this stuff isn't cheap). I cleaned the wall and applied 3 layers of it over 3 months. But the stuff never really dried. UGL tells me it can only be applied to completely dry surfaces (funny, because it's marketed as the ultimate water-proofer). They recommend I scrape it with a wire brush, and kill the mold that's been growing on it with bleach/water.

Be that as it may, it didn't solve my problem of stopping moisture. UGL tells me to dehumidify the whole basement prior to re-applying. However, running a 10,000BTU dehumidifier there for a whole month hasn't helped. The walls get constantly moist from rain.

So how do I best ensure dry walls before framing the basement? My two questions are: Should I address the moisture problem in or out? Each side of the house has a driveway, lined with part cement blocks and part soil.

My second question is, if I can't fully prevent the walls from being moist, should I simply frame the interior of the basement with some sort of moisture-resistant composite material (instead of pine 2x4s) and use cement board? I had wanted to put a fresh coat of cement on the floor as there are cracks and uneven spots, and ultimately tile the floor. I understand that Hardi-Backer is water resistant and completely immune to mold.

I'm attaching some photos from the various parts of the basement. I've owned this house now for a year, and detected no mold growing anywhere in the basement. Only recently, the area where I had applied DRYLOK began showing mold growth (which is spreading quickly). Whatever thoughts or suggestions you have would be greatly appreciated. Thanks beforehand!

http://www.materialized.com/temp/bas...front_room.jpg
http://www.materialized.com/temp/basement/rear.jpg
http://www.materialized.com/temp/basement/front.jpg
http://www.materialized.com/temp/bas...ont_drylok.jpg

gordonf238 04-24-2010 09:36 AM

Just a bump
 
Not to be a pest, but does anyone have any ideas on how to prevent my basement foundation walls from getting moist? Is there some sort of waterproof cement or anything of the kind that I could apply on the walls from inside that would create an effective water barrier?

Daniel Holzman 04-24-2010 09:57 AM

Welcome to the joys of home ownership. First off, your foundation is not "lined with cinderblock", those concrete blocks are the foundation so far as I can tell. Concrete block is relatively porous, because moisture can move through the block, as well as through the mortar used to set the block. Moisture can also move upwards through the concrete floor.

Moisture gets into the basement either through the direct movement of surface water downwards into the soil, and then through the block, or from groundwater movement through the block. If you have a surface water problem, this is best addressed by relatively simple measures such as grading away from the foundation, and making sure the downspouts exit at least ten feet from the foundation and do not leak.

If the problem is groundwater, you have a much more challenging issue. You can determine if you have a groundwater problem by installing a small piezometer (well) in the soil near your house, and measuring the groundwater level. A piezometer is simply an open tube drilled into the ground or pushed into the ground, designed to measure the elevation of the water table. From your description, the problem occurs mostly when it rains, suggesting you have poor control over surface water. So start with surface water control methods, and if your situation does not improve, move on to the more difficult groundwater control techniques.

Typically to control groundwater you need a perimeter drain, which is a perforated pipe that runs around your house, and is typically set about 6 inches lower than the basement slab. The perforated pipe is bedded in gravel, and drains to a sump, where the collected groundwater is pumped out. In some cases, the sump drains by gravity to the stormwater collection system of the city.

Unfortunately, if you don't already have a perimeter drain, and it doesn't seem like you do, it is very expensive to install such as system. There are interior perimeter drain systems which are installed below the floor slab inside the basement, that do the same thing, but they are not inexpensive to install either.

Even with such a system, if the groundwater level is high, you are going to get some seepage through the block. It is essentially impossible to waterproof concrete or block from the inside, to be done correctly you have to excavate all the soil from around the foundation, and a proper waterproofing compound must be installed on the exterior face of the block. Typical waterproofing systems include clay panels, bitumastic materials, PVC layers, and other materials. Once installed, the soil is backfilled, and you will have a waterproof foundation. Combined with a perimeter drain, you will then have a dry basement.

This is not a typical DIY project, it requires machinery and expertise. So far as I have seen, there are no simple, cheap shortcuts that will yield a dry basement. From your description, running a dehumidifier was ineffective, so there must be a lot of infiltration. You may wish to reconsider finishing the basement, as the cost to truly dry it out and minimize mold growth is likely to be high. Covering the walls with a water resistant material like cement board is an option, but will not reduce infiltration, will not dry out the air, and will not prevent mold growth. It will cover up the mold and moisture, which may be of some benefit.

jomama45 04-24-2010 01:19 PM

Excellent post Dan! :thumbup: I couldn't agree more with your thoughts.

Gordon, the pics and descpription are ideal for troubleshooting, good job. The bad news is that there is no simple fix inside of the basement. The Drylok is NOT a long term solution to anyone's foundation water problems. As a matter of fact, I belive that it's a complete farse & waste of money & effort. There is no good reason to try to encapsalate this moisture inside of the block wall cavity, as it will only degrade the block even further if not allowed to escape.

I wouldn't tend to suggest you go ahead & fur these walls out with any material at this point. You definately need to approach this from the exterior first before spending any more money or effort inside.

Best of luck.

Scuba_Dave 04-24-2010 01:57 PM

Keep in mind that cement board is more flexible then sheetrock
It flexes & is not really meant to be used as the only wall covering
I have it on my pool cabana on the bottom 3' since the siding was rotting out
It moves/flexes quite a bit

Gary in WA 04-24-2010 05:01 PM

Nice post by Dan! Understanding basement moisture: http://www.buildingscience.com/docum...gs?full_view=1

http://www.buildingscience.com/docum...ts?full_view=1

Be safe, Gary

itsreallyconc 04-25-2010 06:42 AM

me, too, danny,,, & you've said it before - OFTEN ! you're a great board resource !

gord, in queens, you got a problem - bad enough in nj :whistling2: good news is it ain't a brownstone or row house,,, exterior excavation down to the footer / WATERPROOF the foundation walls / miradrain protection board / backfill w/crush'd stone & excavated fill / proper grading / downspout stuff,,, we also installed an exterior sump & pump on a 14' riser to resolve 1 home.

gordonf238 04-25-2010 04:22 PM

Daniel (and others) Thanks
 
for all your input. So it sounds like addressing the moisture issue from outside should be the first step before I try and finish the basement. The solution however, is a bit more complicated for me, as one side of my house shares a driveway with a neighbor. The driveways on both sides of the house are lined with concrete, so this would mean it would all have to be cut-through or demolished, before the proper drain could be excavated. I can just picture the cost of this project spiraling out of control (and we've just spent around $80k on gut renovation of this house). So unfortunately, I do not have the budget for something of this extent.

Would any of you think lining the basement walls with brick or cement board+tile be an option? Neither brick+mortar nor cement board+tile contain organic elements, so the possibility of mold growth would be very low. I'm thinking I could leave the brick exposed for a nice look. And while brick+mortar are also porous, I don't believe moisture would penetrate to an extent where it would be a problem. Any thoughts?

jomama45 04-25-2010 06:50 PM

Quote:

Originally Posted by gordonf238 (Post 433446)
. The driveways on both sides of the house are lined with concrete, so this would mean it would all have to be cut-through or demolished, before the proper drain could be excavated.

I would consider having the driveway(s) mudjacked at least, if they are pitching to the house. Along with sealing (& maintaning that seal thru the years) the joint between the house & drive.

Would any of you think lining the basement walls with brick or cement board+tile be an option? Neither brick+mortar nor cement board+tile contain organic elements, so the possibility of mold growth would be very low. I'm thinking I could leave the brick exposed for a nice look. And while brick+mortar are also porous, I don't believe moisture would penetrate to an extent where it would be a problem. Any thoughts?

I assume you mean full veneer (full thickness) brick. I'll tell you right now, your slab & wallet probably can't support this option. The bottom joint will always be prone to leakage. And, believe it or not, a brick veneer is much more prone to leakage than a concrete block, as your existing foundation is.

At the very least, you need to remove the interior basement floor around the perimeter & install a draintile system that drains the block & subgrade to a crock. This is a very strenuous job that requires specialized tools AND knowledge. There is undoubtedly serious mass/force present at the base of the foundation wall currently being held by the floor. Removing entire sections of the floor can be extremely dangerous.

These kind of repairs are best assessed from the site unfortunately.
I would think about calling a new foundation contractor, preferably one who doesn't push Drylock as a long term remedy.
Best of luck.


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