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Ask Mr. Crawlspace

What if I have cracks in my foundation walls?

Small cracks in foundation walls may be sealed with caulking, cement or expandable foam. If you can, monitor cracks to see if there's any movement or change in size, and consult a structural engineer if you see any evidence of such. In most [...]

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What about any around holes in my foundation walls?

Holes in foundation walls need to be sealed to prevent outside air from moving into the crawl space.  Use materials such as caulking, cement and expandable foam to seal the holes.  If any holes are larger than a quarter of an inch, you [...]

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I live on the coast. Are foundation vents required for a closed crawl space here?

In your area, installing a vent designed to relieve water pressure in the event of a flood is important. There are vents available that meet flood vent requirements for closed crawl spaces.  Check with your state and local building codes for the placement [...]

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What do I do with my foundation vents when I close my crawl space?

It is best to leave existing foundation vents in place and seal them with a foam insulation board. The insulation board should be cut to the size of the vent and installed from the interior of your crawl space. Once the insulation board is fitted, the edges should be sealed with a caulking and/or foam adhesive.

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I am building a new house. Should I arrange to have vent holes put in my foundation?

No, unless they are required by code in your area.  For a closed crawl space in areas that are not required to have vent holes, just have your mason install the foundation without openings. [...]

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What about the gaps around electrical and plumbing penetrations between my crawl space and living space?

Sealing around electrical and plumbing penetrations prevents air from moving into the wall or living space from the crawl space.Use a caulking or expanding foam that is fire rated for sealing these voids to make sure you meet state and local building code requirements.

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Should I plug up any holes between the crawl space and the house?

Yes, closing penetrations between the crawl space and living space prevents air contaminants in the crawl space from entering the living space. Use a caulking or expanding foam that is fire rated for sealing these voids to make sure you meet state and local building code requirements.

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What’s the best way to insulate my crawl space?

Most building codes allow for several options such as insulating the floor joist system or insulating the foundation walls. In my opinion, insulating the walls is more efficient and, in most cases, is less expensive. [...]

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Do I need to have insulation between the floor joists in my crawl space?

No, not unless it’s required by code. The best method of insulating the crawl space is to use a closed crawl space system with insulation on the inside of the foundation walls. Studies by Advanced Energy have shown savings of up to 18% on new structures using closed crawl spaces and wall insulation. (Be sure to check [...]

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What if my insulation is stringing down and has mold and mildew on it?

Stringing and falling insulation means the insulation has been wet at one time. Wet insulation offers no insulating values, so remove it and remediate the mold and mildew. Be sure to use insulation on the interior of the exterior foundation walls [...]

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