Vapor Barrier

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breckrider

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I'm having my main beam in the crawl space shimmed up. The
structural engineer and the foundation repair guy
have recommended a vapor barrier in my crawl space.

I have vents and the space is dry so is this necessary?
 

havasu

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Absolutely.
I don't know where you live, the water table in the area, or your French drains, but mold is a serious issue.
 

Steve123

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The structural engineer and the foundation repair guy
have recommended a vapor barrier in my crawl space.

I have vents and the space is dry so is this necessary?

I don't think you need a vapor barrier. And my mommy says I am very smart.

But seriously, the structural engineer and foundation repair man both recommend a vapor barrier. And you are looking for a DIYer like me, who has never seen your house, to tell you otherwise ?
 

breckrider

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Point taken but I consider this group pretty well versed in all things home repair. It's expensive though and I've lived in this house for 30 years and nobody else has ever recommended a vapor barrier and no other house in my area has one that I know of. House is in Memphis, TN with a fairly deep water table and I've never had a mold problem. That's why I'm seeking a second opinion.
 

bud16415

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Is the floor of the space just dirt? Are they suggesting putting something over the floor or against the floor joists? Are the floor joists insulated now? If so is there a paper facing on the insulation ether top or bottom? What type of climate do you live in?
 

bud16415

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It's just dirt. No insulation and on the floor. Memphis TN which is hot and humid.
Thanks for the answers. IMO if you have been doing fine all these years without issues such as mold etc you must have sufficient air flow below your structure. When you combine that with your neighbors have similar setups I would say you are fine based on your local. Much of the country your setup might not work well.

If it were me i would likely tell them just do the work I'm asking for and if I notice a change then I will look into the vapor barrier.
 

tomtheelder2020

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Have you asked them why they recommend a vapor barrier? Maybe they just consider it SOP and your personal history suggests it is unnecessary but maybe they are seeing something that needs to be addressed.

When I bought my house 32 years ago, I placed plastic sheeting on soil in the crawl space to reduce foundation movement due to expansive soil. Not a bad idea but increasing moisture in soil under the house resulted in extraordinary root growth. I removed the plastic and live with the minor cosmetic damage due to foundation movement.
 

breckrider

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Have you asked them why they recommend a vapor barrier? Maybe they just consider it SOP and your personal history suggests it is unnecessary but maybe they are seeing something that needs to be addressed.

When I bought my house 32 years ago, I placed plastic sheeting on soil in the crawl space to reduce foundation movement due to expansive soil. Not a bad idea but increasing moisture in soil under the house resulted in extraordinary root growth. I removed the plastic and live with the minor cosmetic damage due to foundation movement.
I have not but I will. I'm still leaning hard towards no barrier.
 

BuzzLOL

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I placed plastic sheeting on soil in the crawl space to reduce foundation movement due to expansive soil. Not a bad idea but increasing moisture in soil under the house resulted in extraordinary root growth.
Where are the roots coming from? How are they getting in there? Obviously, there's no sun for plants in there...
 

Ron Van

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The structural engineer and the foundation repair guy
have recommended a vapor barrier in my crawl space.

I have vents and the space is dry so is this necessary?


Crawlspace encapsulation is big business right now. Many older homes were built with vents to allow airflow in the crawlspace but now, I guess because of central heat and air causing what they call a "Stack Effect" by drawing hot humid or cool air into the crawlspace, they recommend sealing the crawlspace. Here's one of their statements:

"Properties that have exposed or open crawl space vents and external access doors in their crawl spaces are far more likely to experience issues with dampness, humidity, and all the issues that they can contribute to. This is partly because of how they allow water to get into your crawl space during storms, but mainly because of the stack effect and how it can cause condensation.

As such, covering crawl space vents and upgrading crawl space doors to be waterproof and weather resistant is an important part of waterproofing. This will ensure the encapsulation process gets the desired results in the long run."

I'd like to hear the other side of this discussion or theory.

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I'm having my main beam in the crawl space shimmed up.

Last year I wanted to install some new flooring in part of our home so I got my laser leveler out and measured the "levelness" of our floor. It varied by 1 7/8" across the East side of the house. I ended up going into the crawlspace and discovering that the house was built with 2x8" floor joist spanning 13' from the foundation wall to a center beam in the middle of the house. I decided to install an "Intermediate" beam to shorten the span from 13' to 6.5'. I built up an intermediate beam using 2 - 2x6s with a piece of 1/2" plywood sandwiched in-between. I used 2x6s rather than something bigger because space is a problem down there. I used 8 of these beams either 8' or 10' long.

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