How To Partially Encapsulate a Crawlspace | Lowe’s Pro How-To

In this Lowe's Pro How-To, learn the step by step process for how to partially encapsulate a crawlspace.

Shop the tools and materials used in this video:
Moisture Meter -
Spray Foam Insulation -
Tyvek Protective Coveralls -
Project Respirator -
Fungicide -
Condensate Pump -

Step 1: Diagnosis

The first step in any crawlspace remediation project is to do a walkthrough of the property and diagnose the problem. If you’re able to, get a digital diagram of the floor plan from the homeowner or a footprint of the house and land information through GIS before arriving on the property. This’ll allow you to be sure that you are inspecting all potential problem areas when diagnosing the issues on-site.

Begin the inspection process by walking around the outside of the home and identifying any drainage issues. Like, downspouts emptying and draining into the foundation of the home or any grading issues that may cause excessive water to enter the foundation.

After identifying any issues around the outside of the house, go underneath the house and continue the evaluation. It’s best to start where the homeowner thinks the problem is and then work your way to the rest of the crawlspace from there. Take moisture readings in all corners, and the center of the crawlspace, to accurately gauge the overall moisture in the crawlspace. Take detailed notes of all problems.


Step 2: Create Remediation Plan

Now that you’ve diagnosed the problems, create a detailed remediation plan. This’ll be what you present to the homeowner and will also be your guide as to what materials will be necessary to complete the remediation. Spending the time to plan and create a proper remediation strategy in the beginning will save you time and money throughout the job.

Now is also the time to contact an electrician to install a grounded GFCI in the crawlspace to power a dehumidifier, if needed. Do this before the remediation to guarantee there is power for worklights and to power any tools needed to complete the remediation. It also lessens the number of people who will need to access the crawlspace after the moisture barrier has been installed, reducing the possibility of the poly being torn. If possible, have the GFCI installed directly to the main panel.


Step 3: Repair Structural Elements

If the project requires it, the next step is to remove and replace any rotten wood in the crawlspace. This includes girders, floor joists, band joists, and any rotten portions of the subfloor. Make sure to provide any necessary support when replacing portions of rotten wood until new lumber can be properly sistered into place.


Step 4: Remove Debris

Now that the structural elements of the house have been repaired, it’s time to clean out any debris that has been left in the crawlspace from the original construction, previous repairs, or by the homeowner.


Step 5: Fog Crawlspace

Moist environments generate fungal growth and over time that fungus can lead to mold growth. Destroying the fungus before that happens is crucial. To kill off the fungus, you’ll need to fog the crawlspace. This is best done with a cold fogger machine filled with fungicide. Be sure to follow specific manufacturers’ instructions.

If there is any remaining fungus, remove it using a nylon brush and soap and water or a chemical cleaner.


Step 6: Spray Fungicide

Apply a fungus and mold prevention solution to all exposed wood using a sprayer. Adding a dye to the solution will allow you to make sure that you have even coverage and haven’t missed any spots.


Step 7: Seal Vents

Using 1 inch, R5 XPS rigid foam board, measure and cut pieces to fill any vents to the exterior of the house. Once the XPS board has been fit into place covering the vents, use a spray foam to seal around all of the edges.


Step 8: Spray Foam Insulation

Use a spray foam insulation in each band joist bay between floor joists and all along the inside perimeter of the home. This creates a vapor barrier and increases the R value of the crawlspace insulation and helps keep the temperature outside from impacting the temperature inside of the crawlspace.

Be sure to read all manufacturers’ instructions before using. Use only as directed.

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