This article explains how to repair a wood porch post that has rotted at the base.
The author, a Licensed Professional Structural Engineer designed the repair method and used it to repair six porch columns.
It is common for untreated wood porch posts of older homes to have varying degrees of rot, also known as dry rot, in the lower twelve inches or less of the porch post.
The bottom of the porch posts often bear directly on top of the porch decking and begin to rot when the base is exposed to excessive moisture, frequent wetting and drying.
Common causes for excessive moisture accumulating at the base of the porch posts and rotting them are:
- Blocked gutter downspouts which cause rainwater to overflow the gutter and drip directly onto the porch below
- Excessive moisture from mature landscape shrubbery that has grown over the edge of the porch and drips rainwater onto the porch around the porch posts.
- Inadequate deck slope and drainage away from the porch posts.
A summary of the repair procedure is as follows:
Fix the water problem that caused the post to rot
Eliminate the cause of excessive moisture wetting and rotting the base of the porch posts to avoid the base of the porch post to rot again after you have repaired it.
The source of the excessive water that rotted the porch posts was from a blocked downspout drain pipe that caused the roof gutter to over flow onto the porch decking.
Determine the extent of the dry rot
Using a sharp, pointed tool, such as an awl, gently prod the surfaces of the porch posts to locate the rotted areas.
The rotted areas are located by observing where the awl penetrates the wood with very little effort.
Mark the post a couple of inches above the highest location where the rotted wood was observed.
If a small area of rotted wood is observed, the post may be repaired using a less comprehensive repair than is described in this article.
If the rotting is minor, the rotted wood can be removed and the post can be patched with Bondo wood patch filler or its material equivalent.
Contact a Structural Engineer to make the determination of which type of repair is appropriate if you are unable to.
Install temporary shoring
Install temporary shoring to support any loads on the porch posts, such as the porch roof.
Watch the slide show for photos and more information about the shoring process.