If your porch roof is beginning to sag, you will need to replace the porch posts before the overhead structure collapses. Most porch posts are load bearing. This means each post supports the weight of the overhang, which protects the surface area beneath. You will have a minimum of two support posts for this project, with the possibility of more depending on the length of the load bearing structure. Porch posts are commonly made of wood and are susceptible to the weather. Even wrought-iron posts material may need replacing if old and weathered. Some replacement projects are more complicated if, for example, your posts are embedded in concrete or need to be attached to concrete floor or steps.
Step 1: Install Temporary Support Beams
The first thing you need to do when replacing worn out porch posts is to install temporary support beams. Cut 2x4s to the necessary length and wedge these under the overhang beams that need support. Make sure you use enough temporary support beams so the overhang does not come crashing down.
Step 2: Foot Replacement
Determine whether you need to replace the entire post or possibly replace a foot section with a small section of wood. Bottom parts of porch posts receive the most abuse over time, especially in a traffic path. Water can also pool at the bottom of porch posts allowing for wood to rot.
Insects may also get into wood, even treated wood, causing damage to the bottom of a post, requiring repair. If so, make sure the overhang is fully supported at this location and cut away the rotten piece using a reciprocating saw. Measure the open space and cut what will be a spacer piece of wood to insert. Fasten the spacer to the rest of the post using a drill and wood screws at a 45-degree angle. Make sure to recess the screw heads to allow for finishing later.
Step 3: Replace Entire Post
Replacing an entire post is a bit more of a project. First cut the post away from the overhang beam it supports and then remove it from its base attachment. Measure the space between the overhang beam and the bottom base surface.
Do NOT measure the cut-away post since it may now be a different length than needed. Secure the new post to the overhang beam by using either a drill with wood screws or a hammer with nails. Secure the bottom to the base in a similar manner. If the base is concrete, you will need to use either a bracket imbedded in the concrete to secure the post or you can bore holes for bolts through the base and into the concrete using a drill with masonry bit. Bolt the post in place with appropriate hardware for concrete and for the load bearing capacity of the support beams.