Unique vapor barrier help...


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Old 07-20-16, 11:19 AM
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Unique vapor barrier help...

I have a house that has a 5 foot high crawl space. Three side of the house have a covered porch with tongue and groove flooring. The crawl space includes the area under the porch flooring so the entire perimeter of the house and covered porch is enclosed in brick. My question is what should I do about a vapor barrier? I know for a fact that water enters the crawl space from the covered porch when we receive hard rain. Currently the house has a trench dug under the porch leading to the low point of the house with a sump pump. Should I lay vapor barrier down under the house but stop it short under the porch? Is the trench the best option or some type of drainage system? Also, what would be the best "flooring" to install in a portion of the crawl space. I store my pool supplies in the corner next to the entrance door and would like to have something down besides dirt. I know the vapor barrier will need to be down but can I put anything on top of that to keep the plastic safe? Open to any and all suggestions.
 
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Old 07-20-16, 11:29 AM
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Hi Joshua,
What else is down there? With the moisture from the ground and from the porch area you may need to insulate and seal the crawl ceiling/floor and then ventilate the crawlspace. Where are you climate wise?

Bud
 
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Old 07-20-16, 11:51 AM
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Where is the house? Is there insulation under the floor of the main house? Vapor barrier should seal the living area from the damp soil but with no foundation wall between the main house and porch this will be difficult. As far as ground vapor barrier goes there are different thicknesses available. The thickest ones will handle foot and the storage you are looking for. The vapor barrier is usually layed on the bare earth and extended up the foundation walls and sealed to the foundation walls. Maybe you could hang it like a curtain at the edge of the porch to seal off the area under the main house....you would have to be careful about attaching the curtain to wood due to rot concerns.
Can you take some pictures for us?
 
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Old 07-20-16, 12:56 PM
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Thanks for the replies. Currently under the house I have my swimming pool supplies, hot water heater, downstairs air handler, expansion tank for my well, bat insulation between the joists and the sump pump. I believe that is everything other than electrical and plumbing. I am located in Easley South Carolina. I purchased the house last year. The house was built in 1980 and has never had a vapor barrier other than what the last home owner installed before I purchased it. It currently covers about 75% of the crawl space. I will try to get some pictures soon. Currently the plastic just ends roughly at the edge of the living space above. I suppose I could rig up something to span from pier to pier to support the vapor barrier. Any ideas what should be done for the area under the porch? I also thought about installing a footing tile system... Does that sound like a good option? They had a sump pump installed just before I purchased the house but the "french drain" system that was installed is nothing more than rigid pipe laying in the bottom of a trench with gravel on top. It actually floated from a heavy rain not long after we moved in. Thats when I realized I had a flooding issue from the landscape. That has been corrected!
 
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Old 07-20-16, 01:21 PM
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Where's the sump pump located? Is there piping running to it? Where does it eject the water to?
 
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Old 07-20-16, 01:28 PM
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The sump pump is located at the lowest point under the house. It has around 20' of pipe connected to it (10' in each direction). That water is the pumped outside the crawlspace into the yard about 20' away from the house and down hill.
 
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Old 07-20-16, 01:53 PM
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Is the crawl space graded? Sump pump would theoretically end up under the vapor barrier?
 
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Old 07-20-16, 01:56 PM
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I'll wait for the pictures. Bet you didn't think many people would know where Easley is . I have a friend that moved there about 10 years ago. Haven't been down to see him, but we email weekly.

I suspect partitioning the porch areas away from the rest is going to be best advice. That would allow you to condition the space with your air handler and avoid the moisture from the leaky porch.

Bud
 
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Old 07-20-16, 02:41 PM
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haha. I almost put upstate as more people have a general idea where that is. The crawl space slopes with the land. I would say at the front of the house it's about a foot higher (closer to the ground) than the back of the house. Currently the sump pump is exposed, never thought about it needing to be under the vapor barrier or not.
 
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Old 07-20-16, 02:58 PM
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Just trying to get an idea what everything looks like in the crawl space. Wouldn't want the sump under the vapor barrier but if you're trying to seal off the ground need to know what the layout is.
Picture would be really helpful.
 
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Old 07-21-16, 06:36 AM
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I did not have a chance to take any pictures last night. I drew up a quick sketch this morning to show what the layout is. The average ground to joist height is around 4.5 feet. The front of the house (top of sketch) is about 4' clear height and the back of the house is 5' clear height.
 
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Old 07-21-16, 07:13 AM
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Black on white works better but I was able to enhance it to get a look at what you have, thanks.

I don't know how much you are prepared to tackle but I will outline what I feel should be done, and it is a lot. IMO, you need to install a partition wall along the dotted line to isolate the crawlspace under the house from under the leaky porch floors. That would allow the under porch area to remain as a vented space and the under house to become unvented and conditioned. One advantage will be, a new partition wall will be easier to insulate and air seal.

Then, the ground under the house will need to be completely covered with a vapor barrier. Sump pits are available that can be covered with water draining into the pit from below. Radon systems do that all the time.

The remaining exterior wall area that is not under the porch will need to be insulated with air sealing above. The link below will provide some good related information.

Building an Unvented Crawl Space | GreenBuildingAdvisor.com

Bud
 
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Old 07-21-16, 08:03 AM
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Thanks for the info. I did not think about the colors as I usually make pdf's in black/white. I will see what I can do quick to fix that. I will take a look at the link. I wasnt planning to build a wall between the two spaces but if that is my only option then I guess I have no other choice. The porch actually has tongue and groove decking so the leaking is not terrible but it does happen from time to time. I wish I had a way to seal the deck so all of it could be conditioned space under the house.

 
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Old 07-21-16, 08:59 AM
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When converting from a vented space to an unvented, the porch would also present the problem of insulating the bottom of the porch, which can't really be done if it leaks from above. Plus you would need to insulate the exterior walls.

Your climate is not as cold as mine and probably has never gotten cold enough to freeze any pipes.

But, if you read through that article they also talk about air quality. The air in damp musty crawlspaces is not what you want flowing through your home. Yet, during the cooler seasons something like 50% of the air you breathe comes from that crawlspace. In addition to energy savings, that is a very good reason for installing the vapor barrier and separating the porch areas from the under house areas.

You mentioned adding something to the floor to make it usable. I realize your floor is not exactly flat, but if you level it as best you can and then pour what is called a "rat slab" with your vapor barrier under it you will greatly improve that space. With proper planning it could be sloped to eliminate water issues and include drain paths to the sump. A thicker area could be raised to accommodate the partition walls and slope any exterior water away from the house.

It isn't just the floors you would be partitioning, it is the air space, that outside humid air in the summer can create a mold issue when it contacts a cool surface inside.

Bud
 
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Old 07-21-16, 10:55 AM
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Thanks Bud. I will look into the rat slab also. The ground has a very steady slope for the most part. I want to do some leveling anyway.
 
 

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