Crawlspace question

Tom Elam

Basement systems did our crawl space this January. We had heavy rain in Maryland the past few days and the space is dry. We are satisfied customers.
Tom Elam

Wayco Wayne_2

A customer of mine

has a problem with a humid crawlspace. He says it gets so moist it smells and the smell finds it way into the envelope of the house. He currently has dehumidifiers down there, but was wondering if a couple ERV's might benefit his situation. Does anyone have any insight to this situation? I have alerted him to this thread and he will be joining us to see if anyone has any ideas. WW

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Tim P._2

I think the first thing to do would be to install a vapor barrier. Run some 6 mil poly down the crawlspace.

HRV and dehumidifiers may be a bandaid solution, but I think the real source of the problem is lack of vapor barrier.

How old is the house? What type of construction? How close is the water table?

Good Luck,
Tim

Brad White_9

I am with Tim

Mitigate first, dehumidify last.

I had a client once who had a running spring it seemed through her foundation and basement. Just a bad leak. Rather than fix that, for years she ran a dehumidifier, spending hundreds on electricity for at best a "feel-good, I am doing something" effect. If she dropped the RH down five percent for all that effort I would be surprised.

My only concern about laying down poly sheeting is that yes, it does trap the moisture but is never really vapor tight to the house. What you wind up with below the sheeting is a Club Med for mold. Spores are there but the moisture now condenses into a theme park.

In addition to the vapor barrier and if budget allows, covering the basement with Nudocrete (sp?), a Gunnite-like shot concrete product, will seal it well. I have seen that used on some old houses built on ledge with lots of fissures and springs.

hot_rod

checkout this company

I picked this literature at a homeshow recently. Could be a nice profitable side business :)Maybe there is one in your area aready?

www.basementsystems.com

hot rod

Brad White_9

That is the stuff!

You got it, HR. May go by a different name but it is an almost soft concrete that goes in like elephant poop (I suppose), fills every crevice and levels pretty well. Dropped the RH in the crawlspace (once it cured) to near outdoor ambient levels.

EDIT: It "looked" poured in place! I guess it is a sheet/roll product. Still...

Weezbo

WW, it goes deeper....

one of the saddest things that you will see with overly humid crawl spaces is what "reactive" perscriptions at repair uncover...

if at all possible the ventilation to fresh outside air by natural draft means,.. removal of loose insulation at the rim and box beams ..get it all out first... then when no one is down there, add ventilation intake and exhaust fans....i think cranking up the heat helps carry away the moisture...then, you need to take a sharp look about for any signs of mold...placing a vapor barrier on the ground sealed with tremco is in order...insulation like spray foam doesn't stick to water so, getting the place dry is real important before you have the edges and corners foamed is real good idea..

abatement can get a little tricky as positive pressure will drive moisture into the building materials...use reverse Weezbo construction technique for abatement.. insulate ventilate and heatalate...the not too late part stays the same though

i am positive, that from time to time ,new homes are built that are ruined by mold. as many people have had these experiences, it would benefit you to get someone from an abatement or mold inspection service for on site consultation with a *wrench:)



that will help catch corners that might go unaddressed in your endeavours...

*
Test instruments

hot_rod

InsulTarp, white side up

is also nice in crawlspaces. I use 4 foot wide rools just for kneeling pads when I work in crawls. Expensive for just a vapor barrier, but it has some r-value.

hot rod

The Wire Nut

Have a look over at buildingscience.com

They have some articles that expressly focus on wet basements, and how to treat them. I second the 6mil poly or TuTuff layer to seal the water out. With the right drainage and a sump pump in a can (below the vapor barrier), the water will be largely a thing of the past.

If possible, follow up with insulation. Without light and heat, it is extremely unlikely that mold can establish itself below the vapor barrier. Plus, the homeowner benefits from lower heating bills. Also, eliminate any crawlspace vents the place has.

Once the basement is part of the conditioned space, insulated, etc. the humidity should plummet.

Patchogue Phil_29

Brad

I am curious.... that Gunnite-like product, wouldn't the "Club Med for mold" happen under it the same as plastic?

don_185

When living in

When living in a arid climate..ventilation is not the answer.

If you were to take 100 cfm of 70 degree dew point air entering a crawl, you would need to remove about 10 gallon
of water per day.

In my area of tidewater we have to seal crawl spaces..add
a good vapor barrier and most importantly checking drainage away from the house to solve the problems.most often the landscaper raise the flower beds every year.

Most people fail to realize that crawl spaces are the major
source for air filtration thats permeates up into the living
area.

I'm at a customer house now adding some steam rads to the new addition and she apolizing for the smell in her house.
She keep a clen house and she just has no clue of where the smell is coming from.

After acouple of day in the crawl I was able to explain that no its not a dry trap...its the cats, they have turn the crawl into a litter box.

Brad White

Yes it would but

with the plastic, the barrier between your house air and the Club Med is pretty thin indeed (0.006 inches!)and not well sealed in normal practice.

The earth's soil is full of pathogens below our slabs and concrete in it's many forms at least puts them out of site, mind and lungs.

That is my take anyway.

STUART WASHINGTON D.C.

WATER IN CRAWL SPACE

Im a little desparate for ideas..... I had my contractor dig my four foot crawl space down to eight foot deep in feb 2007. since he finished it has flooded three times after significant rains. We have worked on outside drainage and it hasnt helped. I think we went down 1.5 to 2 feet deeper than the concrete footers along the exterior of the space. The space is beautifully finished with sheet rock walls and tiling however I am very suspicious that my contractor didnt put in the vapor seal along the floor and walls that I had requested and I am suspicous that the flooding is due to the ground water level rising above the floor level of the space. The space will take in about 1/2 inch of water which will cover most of the perimeter of the floor. I have identified that the entry point of the water is along the external wall of the crawlspace/house. What to do now.... ripout everything and place the vapor barrier and possibly a sump pump or is their any point to try to put a foot of dirt back to raise the level of the crawlspace....Is there any less radical solution? My level of confidence in my contractor is low yet I sense that he has contributed to this screw up... and he should help to fix it...only I am not that likely to trust his suggestions.... any ideas?

STUART WASHINGTON D.C.

WATER IN CRAWL SPACE

Im a little desparate for ideas..... I had my contractor dig my four foot crawl space down to eight foot deep in feb 2007. since he finished it has flooded three times after significant rains. We have worked on outside drainage and it hasnt helped. I think we went down 1.5 to 2 feet deeper than the concrete footers along the exterior of the space. The space is beautifully finished with sheet rock walls and tiling however I am very suspicious that my contractor didnt put in the vapor seal along the floor and walls that I had requested and I am suspicous that the flooding is due to the ground water level rising above the floor level of the space. The space will take in about 1/2 inch of water which will cover most of the perimeter of the floor. I have identified that the entry point of the water is along the external wall of the crawlspace/house. What to do now.... ripout everything and place the vapor barrier and possibly a sump pump or is their any point to try to put a foot of dirt back to raise the level of the crawlspace....Is there any less radical solution? My level of confidence in my contractor is low yet I sense that he has contributed to this screw up... and he should help to fix it...only I am not that likely to trust his suggestions.... any ideas?

Bob Grindod

Crawlspace question

A modest proposal: bring the crawlspace (CS) all the way inside: seal the floor: poly sealed to the supports and toe walls. Seal the walls: spray foam or poly over the block, Insulated the walls and the band joists. This is a recommended practice in Home Perforamnce circles. I have seen this work many times. The cs is dry!
Ventilation in a crawlspace to keep it dry does not work because the temperatures are low and the moisture input easily overwhelms the capacity of natural ventilation. Winter: cold air entering the cs will cause condensation of high mositure content air in the cs. Inthe summer very humid and warm air will condense in the CS. Bringing the CS inside removes the source and warms the space. An HRV with plastic on the ground is OK, just keep in mind that the plastic must be sealed to the walls and walls should be treated too, and now you have another mechinical device to maintain.