How to Replace a Rotten Wood Porch Floor

A wood porch floor can rot and deteriorate over time due to exposure to the elements. When replacing a porch floor, be sure to use pressure treated pine or other rot resistant wood for both the joists and flooring.

It’s a good idea to prime all four sides of tongue and groove flooring before installing it to reduce expansion and contraction due to changes in temperature and humidity.

Pressure treated flooring that has been kiln dried after treatment can be painted right away. Flooring that hasn’t been dried after treatment should be stacked with spacers between the boards, protected from getting wet, and allowed to dry for at least 30 days before painting.

After the old flooring has been removed using a crow bar, replace any rotten floor joists with treated lumber before installing the flooring.

Use a rubber mallet or a scrap of the flooring as a protective block when tapping the floor boards together. Blind-nail the flooring in the tongue using galvanized or stainless steel finishing nails.

After the flooring has been installed, apply two coats of porch and deck enamel paint to protect the top surface. Watch this video to find out more.

Further Information

• How to Repair Rotten Porch Flooring and Railings (video)
• How to Remove and Replace a Wood Porch Column (video)

VIDEO TRANSCRIPT
Danny Lipford: An aging wood porch may have decay in the porch boards themselves, in the framing that supports it, or both. Bouncy or springy floors are often the result of inadequate or damaged joists in the middle of a span.

If there are signs of damage in the porch boards, start by removing them. Now this is a simple process of prying them up with a crow bar, unless the rails and columns rest on top of the deck boards.

To lift a support column you’ll need to use a hydraulic jack and another post to temporarily lift the weight of the roof above. This will relieve the column and allow you to remove the boards that are beneath it.

Here the ledger board that supported one of the joists has rotted and detached from the band joist on the outer edge of the porch. We’re replacing the damaged section of ledger with a new pressure treated piece of lumber.

Because there is some rot in the loose joist, too, we’re adding another two-by-eight alongside it to help support it, which is called “sistering” the joist. The two boards are nailed together numerous times over their length, and the new one is attached securely to the band joist to replace all the lost strength.

Now it’s ready for new porch boards. This material is pressure treated, tongue and groove one-by-four that is kiln dried after treatment. That means we can prime it right away rather than having to wait 30 days or so. We’re priming all sides before we install it so it won’t absorb moisture and swell or cause the paint to blister.

The trick to installing a tongue and groove porch floor is getting the boards pressed very tightly together before nailing them down. A scrap of the tongue and groove material makes a handy tap block so you don’t damage the edges of the boards.

A pneumatic nailer makes driving galvanized finish nails through the groove side of each board a lot easier.

Once the porch boards are all down, it’s a good idea to add some trim around the edges before finish painting. For the longest wear, be sure to apply two good coats of porch and deck enamel to protect the surface from future damage.