Tips on Drying Out a Damp Crawlspace

In some older houses, basements are smaller and not high enough for people to stand up.  These are known as crawlspaces and were primarily designed to keep air circulating through the home.  While they are not suitable for living spaces, they can be used for storage. And they do need to be kept free of damp or they can become a prime spot for the growth of mold or mildew as well as other pests that like warm, damp spots.

damp spaces in home

That’s why if your home has a crawlspace, it is important that you keep it dry and stop the potential for damp problems.  It will also reduce the risk of infestations of things like spiders, rats or even woodworm.

Dealing with the Damp

Before you add any measures to stop future damp problems, you need to handle the issues you already have.  To start with, you will want to get the space dried out. A dehumidifier is one way to do this, a commercial grade product that can remove large amounts of moisture from the air and make the crawlspace drier.  You can also get smaller, domestic variations that are ideal if there is a little moisture in the room, but it isn’t actively wet.

improve drainage

Improve the Drainage

The first thing to look at is the drainage in the crawlspace.  Depending on the age of the building, this might be virtually non-existent as an understanding of damp and how to handle it is a more recent development.  Having the right drainage under and around the house will ensure that water is directed to the drains, not pooling around the house where it can easily be absorbed into the crawlspace.  

You may need to look at the lay of the ground around the house and have this checked by an expert.  If this works against you, it could be sending water towards the house rather than away. Also, ensure guttering is in good condition and works smoothly.

insulate the foundation

Insulate the Foundation

Having insulated and waterproof foundations to the crawlspace are the next important step.  Something like 1.5-inch rigid insulation can work well and it can have tape on the seams to prevent air and moisture passing through.  Ensure the rim joints of the foundations are also insulated and use caulk on any seams to stop that moisture escaping.

Add a Moisture Barrier

Another way to ensure water doesn’t get through the floor is to add a moisture barrier on top of the insulation.  A heavy duty plastic, moisture barriers come in different thicknesses and the thicker the better for a crawlspace.  Aim to add it to the floor in a continuous run and make sure there are no accidental holes or punctures as this will impair the barrier’s effectiveness.

Add Plastic Sheeting to Walls

As well as covering the floor, you should also do something about the walls of the crawlspace.  Plastic sheeting can work well for this job and can be added to the walls then galvanized flashing used to keep it in place.  This will form a strong moisture barrier that sends moisture back out of the crawlspace and prevents damp. See here on how to treat damp walls.

Keeping The Damp Away

You may also want to improve the ventilation in the crawlspace as this will play a big part in ensuring the damp doesn’t come back.  Something like an electric fan can help with this if there is already some ventilation in the room. If there isn’t, you might want to talk to an expert in damp proofing about improving the ventilation so you don’t end up with condensation problems that your damp proofing measures can’t stop.

tips on drying out a damp crawlspace

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