How to Build a Foundation Vent

Foundation vents provide ventilation in crawlspaces during hot and wet periods of the year. Without proper ventilation, the hot and humid air in the crawlspace promotes wood rot on the floor joists. The trapped humidity in the crawlspace may also lead to mold growth, which can then work its way into your house. Purchase a foundation vent with openings you can open and close with a lever, allowing you to close off the vent during the cold months.

Foundation vent
Black marker
Drill with mason bit
Safety goggles
Work gloves
Cold chisel
Hammer
Cement mix
Bucket
Trowel
Rag

Instructions

- 1
  Hold the backside of the foundation vent against the house’s foundation, where you plan to install it. Trace around where the vent contacts the foundation, using a black marker.
- 2
  Drill holes through the tracing you made, using a drill with a mason bit. Make holes in the exact corners of the tracing, and then space the rest of the holes you drill a quarter inch apart.
- 3
  Put on safety goggles and work gloves before continuing. Place the tip of a cold chisel at the inside edge of the holes you drilled. Strike the end of the chisel with a hammer, breaking away the foundation inside of the tracing.
- 4
  Place the vent in the opening you created, testing how it fits. Chisel away any pieces of the foundation that keep the vent from fitting in the opening.
- 5
  Mix cement and water in a bucket, following the ratio on the mix’s bag. Remove the foundation vent from the hole you made, and then apply a quarter inch of wet cement to the edges of the opening, using a trowel.
- 6
  Insert the foundation vent back into the opening in the foundation. Use the trowel to pack in more cement to fill in gaps and to level the space between the vent and foundation. Clean off any cement that gets on the vent’s openings, using a rag.

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