How to Replace Foundation Vents

Updated on April 3, 2019
Working foundation vents help prevent damage to your house sill plate due to rot or termites.
Working foundation vents help prevent damage to your house sill plate due to rot or termites.

The foundation vents on your home help to prevent moisture from getting under the house by providing air flow. Excessive moisture leads to rotting wood and termites. Keeping the vents open during the summer allows air to flow under the home, keeping it cooler and drawing out moisture. They also help to ventilate when propane or gas lines are running under the home.

Closing them during the winter, or even during strong summer storms, helps prevent snow and rain from going directly under the home. Closed foundation vents during the winter also help to keep the pipes under the house from freezing due to cold winds.

Loose, missing, or damaged foundation vents require replacement. They are usually made of steel, have a screen, and are installed with mortar. There is a handle that allows you to quickly open or close them depending upon the weather and the season. Replacing them requires making sure the hole is free from any loose mortar from the previous vent.

What You'll Need

  • Cold chisel
  • Hammer
  • Stiff wire brush
  • Quick-drying mortar
  • Bucket
  • Trowel

Step 1: Remove the Existing Foundation Vents

  1. Pull loose foundation vents out of the hole if the vents are so loose that they have no mortar holding them in place.
  2. If they're mortared in, chip the mortar away from the perimeter of the hole with a cold chisel and hammer. Avoid digging into the foundation; the mortar is relatively thin and should chip away with little difficulty.
  3. Pull the center of the vent. If it doesn't budge, go into the crawl space and look for mortar adhering from behind. Chip away the mortar and remove the foundation vent from the hole.
  4. Remove the old mortar from the hole with the chisel and hammer. Brush the inside perimeter of the hole with a stiff wire brush to remove all traces of the old mortar. Pay special attention to the corners of the hole.

Install New Foundation Vents

  1. Mix quick-drying mortar and water in a bucket, according to the directions on the mortar bag. The mortar consistency should be like thin oatmeal.
  2. Apply a thin layer of mortar along the inside perimeter of the foundation vent hole with a trowel. The layer should be less than 1/4-inch thick.
  3. Position the new metal vent into the hole. Apply another layer of mortar along the outside perimeter with the trowel. The mortar should overlap the edges of the vent and the inside of the foundation vent hole an inch on each side. The mortar should also be less than a 1/2-inch thick.

Foundation Vent Options

Metal is the most common material, but there are also plastic replacement vents available that require no mortar. These secure with a series of screws. The vent hole still requires cleaning just as you would when installing a metal vent. Follow the directions that come with the replacement vent you purchase.

Another option is to install automatic foundation vents. These remove the guesswork of when to open and close the vents. They open and close automatically depending upon the weather and temperature. Again, refer to the manufacturer's instructions for installation and to determine if an electrician is needed for wiring.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.


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    • kenwrites profile imageAUTHOR

      Ken Crawford 

      5 years ago from Yreka, California

      Lowes or Home depot

    • profile image


      5 years ago

      Where can I find the foundation vents that don't need motar? I do not want the automatic ones. All that I can find are the mortar types.


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