Porch Post Rot Repair: Fix the Bottom or Replace the Whole Post?

Why porch posts rot from the bottom up

A wood post is a bundle of straws. The end grain at the bottom is thousands of open straw ends standing on concrete, and concrete holds moisture for days after every rain. The post does what straws do. It drinks.

The top of the post is protected by the roof and sealed by paint on face grain, which absorbs water slowly. The bottom sits in splash from the steps, snow piled against it in January, and that damp concrete. Paint on end grain fails fast, and once water is inside, the paint film actually makes things worse by trapping it. Rot fungi need wood above roughly 28 percent moisture content to get going, and the bottom two inches of a porch post spend half the year there.

That is why you see posts that look perfect from four feet away and crumble at the base. The rot works from the inside of the bottom, hidden behind an intact paint shell.

The screwdriver test: find out how deep it goes

Before anyone talks money, probe the post. Take a flathead screwdriver and push it into the wood at the base, on all four sides, with firm hand pressure. Sound wood stops the tip within a sixteenth of an inch or so and feels solid. Punky wood lets the tip sink a quarter inch or more with a soft, dead feel.

Work your way up the post in two inch steps until the wood firms up, and note the height where it does. Check the back side facing the wall, because that face dries slowest and often hides the worst of it. Tap the post with the screwdriver handle too. Solid wood rings, rotted wood thuds.

What you learn decides the route. Rot confined to the bottom 1 to 3 inches is a trim and lift job. Rot running 6 inches or more up the post, or soft spots appearing higher up around joinery, usually means splice or full replacement.

Route 1: cut off the rot and add a standoff base

When the damage is shallow, the cleanest fix is to support the load, cut the bottom inch or two of the post off square, and set it back down on a galvanized standoff base. A standoff base is a steel bracket that holds the post about an inch off the concrete, so the end grain never touches a wet surface again. The American Wood Council DCA6 guide shows this same hardware logic for deck posts, and the physics on a porch are identical: wood on concrete rots, wood above concrete lasts.

We seal the fresh cut end with two coats of oil primer before it goes on the bracket, then wrap the base with a trim ring or PVC block so you see clean molding instead of steel. Done right, the repair is invisible from the sidewalk and the post is drier than the day it was installed.

Route 2: a partial splice for turned or custom posts

Some posts are worth saving above the rot. Turned Victorian posts, chamfered posts with beaded corners, profiles that have not been milled since the Eisenhower administration. For those we cut out the rotted section and splice in new wood with a half lap joint, structural screws, and exterior epoxy, then shape the new section to match the old profile.

For shallow surface rot on a decorative post that still has solid structure behind it, a two part epoxy consolidant and filler system is legitimate. It penetrates the softened fibers, hardens them, and takes paint well. The honest limit: epoxy is for cosmetic and shallow structural loss, not for a post bottom that has lost half its cross section. Filling a structurally gone post with putty is sculpture, not repair.

Route 3: full replacement, with the roof held up first

When rot runs deep, the post comes out. The sequence matters. First a temporary support goes in next to the old post, either a screw jack post or a doubled 2x4 tee, snugged up until it just takes the load. Then the old post comes out, the bearing surfaces get inspected and repaired, and the new post goes in tight with a standoff base underneath.

For the new post we use solid treated lumber wrapped in cellular PVC, a fiberglass column, or clear cedar, depending on the porch and the budget. Treated wood wrapped in PVC gives you structure that resists rot and a skin that never needs more than paint on your schedule.

• Never pull a roof bearing post without temporary support in place, even for ten minutes
• Check the beam above the post for crush or rot before the new post goes in
• Size the new post to match or exceed the old one, not to match what the box store had
• Prime all six sides, especially both end grains, before installation

The structural caution nobody should skip

Most porch posts are not decoration. They carry the porch roof, and in this county a porch roof carries real snow load on top of its own weight. A post that has quietly gone soft is often already letting the beam sag an eighth of an inch, and the roof has settled into that shape. Yank the post out without shoring and you can crack the beam, tear the roof connection, or worse.

If your post has visible crush at the top, if the beam above it dips, or if the porch roof has a wave in it, that is past the DIY line. The repair is still routine for us, but the sequence and the shoring are the whole job. This is also where we tell you the thing some contractors will not: if one post is rotted and the other three probe soft, replace all four in one visit. Mobilizing a crew four separate times over six years costs you far more than doing it once.

What porch post repair costs in Lancaster County

Around here, the going rate for a simple cut and standoff base repair is about $250 to $500 per post. A full swap of a non bearing post runs $450 to $900, and a roof bearing post with temporary shoring typically runs $850 to $1,700. Our jobs usually land closer to $230 to $450, $400 to $825, and $800 to $1,550, because one in-house crew handles shoring, carpentry, and paint in the same visit instead of scheduling three trades.

If the posts have gone, the steps and railings are usually not far behind. A steps rebuild runs $800 to $2,500 and a railing run is $500 to $1,500, and bundling that work into one mobilization is meaningfully cheaper than three separate service calls. You can see a complete revival of a tired porch in our Lancaster porch refinishing project, and the full menu on our porch and deck refinishing page.

And the flip side, honestly: if you have one post with an inch of soft bottom, you are handy, and you own a saw, route 1 is a Saturday morning and a $25 bracket. We would rather you do that than pay anyone a service minimum for it.

Prevention: keep the new post off the concrete

Every porch post we install or repair gets the same details, because they are the difference between 8 years and 40. The post stands on a standoff base, never on concrete. Both end grains get primed before assembly. Trim rings get caulked at the top edge only, so any water that gets behind them can drain out the bottom instead of ponding inside.

Beyond the post itself, look up. Most chronic post rot has a water source: a gutter that overshoots, a downspout dumping beside the steps, a porch floor pitched toward the post instead of away. Fix the water and the wood stops fighting a losing battle. It is the cheapest structural repair there is.