Crawlspace Issues

[beckhamk]

For our cabin we went with a crawl space that is 7 corse, it was supposed to be 5 but the contractor misjudged the fall and had to add two corses.

The foundation was sealed with some black or tar looking sealer for everything at and below the grade.  There is drain tile all around the foundation and that goes to day light down the hill.  There is some backfill around the foundation but not completely due to us doing the build ourselves and the contractor not being to get back due to wet conidtions in the fall/winter.  So in the next two weeks the contractor will be back to grade and backfill around the foundation.

We built the cabin during one of the wettest springs and summers on record here in ohio. So we had 2-3 in of water in the crawl during the build process. Once we got the floor on we used a builge pump and removed all of the water.  there was already gravel in the crawl, so we put down two layers (overlapping) of plastic vapor barrier then put more gravel on top of most of the crawl (had to bag that in).

Anyways the last time we were in there it was dry as a bone on the new stone which was around oct.  We had to get into the crawl this weekend and notice that a good portion of the crawl seemed damp.  As in the rocks are wet looking compared to the ones that are dry.  When i got it I could see that the most of the walls look damp and that there was some water pooled in a few spots. Almost as if the water condenses on top of the plastic.  I sucked out about 2 - 5 gallon buckets  there is still a little bit here and there.  We also had all of the vents close in the crawl for the winter.

I am looking for ideas as to how the water it condensing on top of the plastic and should i consider poking a few holes in the plastic to let the water drain under the plastic into the ground.  This weekend we sealed the exterior of the block wall (above grade), which i am not sure if that will help the damp inside walls or not, but my current house has this on the above grade.

I also did not see any dampness on the floor joists or on the sill plates. I am also woudnering if this is also a side effect of the backfill not being there all fall/winter.

Thanks for your insight.

Kyle

[Don_P]

These are tough to diagnose. First thing is to establish grade sloping away, that may and often does fix it. If the plastic is pinholed or just lapped and depending on the edge treatment, the moisture could be from either condensing vapor or bulk water moving thru. Is the interior grade above the invert, bottom, of the footing drain?

I'd open it up and run fan(s) to both warm and dry it. Daytime air temp will raise the temp of materials under there above dew point and moving warmer air will transport moisture out of there faster. Alternatively seal and dehumidify. It might be a good idea to get a cheap thermometer/hygrometer from Walmart or Lowes and check the relative humidity before and after and while experimenting.

[PEG688]

  We also had all of the vents close in the crawl for the winter.

  Worst time of year to close the vents , not that there is a 'good' time to do this.  Open the vents and throw away the vent covers , more than likely your "problem" will go away with the vent covers.

   

[itpdk9]

I would put a french drain pipe around your foundation before you back fill, its cheap and will help with water issues.  just my 2 cents

[PEG688]

I would put a french drain pipe around your foundation before you back fill, its cheap and will help with water issues.  just my 2 cents

He said he has a drain tile  " There is drain tile all around the foundation and that goes to day light down the hill."

I wonder if it's lower then the footing?  We have a house right now that has issues with water , the french drain / perimeter drain but it was set at the same elevation as the footing bottom, we dug it up and put a lowered trench about 18" away from the footing , dug 12" deeper than the footing bottom. Seems to be working , time will tell.     

[Don_P]

One of the arguments against venting with outside air is that the crawlspace is cool and humid outdoor air can condense on cool stuff under there. If there is sufficient airflow to warm it under there then that can keep it above dew point and the airflow can begin to dry it. The humid southeast is prime for this. So there is the argument for sealing the vents and conditioning the air by dehumidifying or including it in the hvac envelope.

But, this is probably the moisture that was trapped under there or moisture from the lack of grading. I'd start with grading and actively venting it for awhile to see if that dries it out. If it does, switch off the fans and see if the relative humidity climbs significantly again. At that point, time to visit this again.

[MountainDon]

I've bought relatively cheap thermometers combined with a hygrometer at Lowe's. Even ones with remore reading capabilities. Could be very handy. I have one that records the max and min and holds the greater/lower number until reset. The numbers keep me occupied / amused / entertained.

[rick91351]

Was the french drain installed properly?  Where it day lights is there evidence of moisture being carried away from you dwelling.  Do you have a spring coming up under your house?  If so your french drain might not work, but need to install an other other type of drain...... 

Springs with all forms of hydrology points to the path of least resistance,  When you dug the clearance for your dwelling did you alter the path of least resistance?  Not all springy areas produce a lot of water some just enough to be a pain instead of a blessing ......

   

[beckhamk]

Got an update on this...  good / bad.....

I believe we have the water under control. We now have been backfilled, gutters installed and we installed a french drain to remove the excess water that will come in. I know you will never get all water out.  So all is good there...  Since we left the original vapor barrier in place we cut through it for install of the french drain and then installed all new vapor barrier plastic over top.  All was looking good.

New issue - now we have condensation in the crawlspace.  We have four vents in the crawl which are open.   How should we address this condensation....

I was thinking i needed to get a solar vent fan and fan out the moister that is in there now to get things drying and maybe even put a screened door to get more air flow.  But I am reading that the humid summer air will make it worse.   Seems to me that we need to dry this out with fans then seal off all of the vents and doors completely.

thoughts?

[beckhamk]

Actually spoke with my foundation contractor and he has suggested removing the plastic we put up on the walls.  Said to leave the vents open, remove the plastic on the walls, leave the plastic on the floor.  said the blocks will help suck up the moisture.

any thoughts on this?

[Don_P]

Do everything you can to keep the water out, that sounds like the problem. If there is liquid water getting inside you are going to be fighting an energy consuming uphill battle to keep it under control. Condensation of humid summer air is squat compared to trying to vaporize and evacuate liquid water. First question is, where is the liquid water coming from and how can you redirect it around the foundation? That might mean another deep drain around the uphill side out in the yard running to daylight. Yes that is a big onetime chunk of cash but running fans or dehumidifiers is a constant drain and all depending on the amount may or may not work. As far as the summer condensation of humidity on cool underfloor surfaces, one solution is to keep those surfaces above dewpoint. Active ventilation, fans, during the day does admit humidity but also heat. You're playing a fine line if it's 90 degrees and 90%RH and its damp under there, the air won't have much water carrying capacity and it will cool. You can add heat to lower the RH and increase the carrying capacity and then vent that hot moist air over and over but that is going to smart. A dehumidifier will add heat and provide a cold coil to condense on but isn't cheap to run either and you'll need to start adding or size them until you have enough capacity to take care of the leak.

It is no different than having a hose running on the floor and trying to blow the floor dry while that hose is running. Turn the hose off if you can.

[flyingvan]

    I solved my moisture problem with a two pronged approach---first was a sump.  Digging in a crawlspace isn't very fun, but I went down 6' (I'd chip at it and pull out the waste with a shop vac) poured a little concrete in the bottom and set a 10" PVC pipe in it vertically.  There were weep holes drilled in the pipe at about the 14" mark.  Then filled all aroung the outside with gravel and dropped in a sump pump.  When there's really strong rains, you can hear it running under there but the soil above stays dry.
    Second---I ran a 4" ABS pipe from the crawlspace, though the house, up into the attic.  Natural chimney effect just pulls air through, providing pretty decent air exchange for the crawlspace.  You don't really get active flow through crawlspace vents since there's no pressure differential but when your attic warms up the air circulates nicely.  On a hot summer day if I go up there you can feel the cool air flowing from the pipe.  Warning---this is NOT to fire code.  If you ever get an attic fire it's going to torch quicker, but I figure 4" of pipe won't add that much airflow compared to the gable vents anyway

[beckhamk]

Just wanted to give everyone here an update on this.... We called our the basement dr company to take a look at this.  Said we did everything right with putting down the plastic on the walls and floor etc.  Didnt try to sell us their 20 mil plastic.  Did say we should close off the vents, so we covered them up with plastic until the new outside vent covers come in. We are also going to get a crawlspace dehumidifier to remove the excess mositer that was in there.

The issue is that the vents do circulate the air, but also bring moister with it on the hot humit steamy days. So once that hits the cooler metal duct and pipes it condenses.  Once we has the crawl dried out, we sealed off the vents from the inside with plastic as a test and it worked perfectly - no condensation!   

After a few weeks with no issue , we had the inside foamed in to help seal it off and to keep it warmer in the winter down there with the water lines etc.