· by Michael Blair, Nashville's Deck
Search for screened porch repair and most of what comes back is about rolling new mesh into a frame. That is often all a porch needs. But on porches around Nashville that are ten or twenty years old, the torn screen is usually the thing you notice, not the thing that is wrong. The wood the screen fastens to, the floor it stands on and the posts that hold up the roof all sit where water collects, and that is where a porch actually fails. This is how we sort a screen job from a wood job, what changes once the framing is involved, and why the damage keeps showing up in the same few places. The services themselves are on our screened porch page.
A screen job or a wood job
A screen problem looks like this: mesh with a tear or a pet-sized bulge, a spline that has shrunk and let the screen pull loose from its groove, a panel that sags because the track or trim holding it has worked free. If the wood around the opening is hard and dry, the repair is mesh, spline or track, and it is the quick part of porch work.
The wood problem hides behind the screen line. Before quoting any screen repair we push a screwdriver tip into a handful of spots that tell the story: the bottom rail of each screen opening, the floor boards along the outside edge and at the door, the base of each post where it meets the floor, and the sill or rim board the whole wall sits on. Sound wood resists the tip. Rotten wood lets it sink in, often with the paint still looking fine on top, because paint holds its shape long after the wood behind it has gone soft.
A soft bottom rail matters more than it looks. It is what the screen tensions against, so new mesh on a rotten rail pulls loose again within a season. A soft post base matters most, because on most porches the posts carry the roof.
- Torn or bulging mesh, loose spline: a screen repair
- Soft bottom rail under the screen: rail replacement, then new screen
- Spongy boards at the edge or the door: floor repair
- Soft post base or sill: framing repair, with the roof supported while it is done
Why the damage is always low
The roof keeps rain off the top of a screened porch, so it is easy to think of the wood inside as protected. It is only partly protected. Screens stop insects, not wind-driven rain, and a summer storm here pushes water through the mesh and onto the floor along every wall. Leaves, pollen and the grit that comes with them blow in through the same mesh and settle against the bottom rail, where they hold that water for days.
The USDA Forest Products Laboratory’s Wood Handbook chapter on biodeterioration explains why that spot goes first. Decay, molds and stains in wood come from fungi, and fungi need a food source, which is the wood itself, along with suitable temperature, moisture and oxygen. Take one of those away and the wood lasts; where all of them are present, protecting the wood is what decides how long it holds up. Middle Tennessee supplies the warmth and humidity for most of the year. The bottom rail and the floor beneath it supply the moisture, and the oxygen is always there.
Shade adds to it. Many of the porches we see sit on wooded lots, facing a back yard full of trees, over clay soil that stays damp, and the floor along the screen line can stay wet long after the rest of the porch has dried. If the porch floor is open underneath, the space below it matters too; we wrote about that in our post on keeping the space under a deck dry.
When a repair turns into a permit
In Davidson County, the rules we look at first for a porch floor are on Metro Nashville Codes’ Add Deck page. That page is written for decks and does not mention screened porches, but a screened porch floor framed on joists is built like one, so we ask Metro rather than assume. Its lines on repair are specific. Replacing more than 100 square feet of deck boards needs a permit. Replacing any footing or framing needs a permit. Tearing a deck down without replacing it does not, and replacing a deck or building a new one does.
Put against a porch, that means a few rotten floor boards near the door are usually a straightforward repair, while a floor that has to come up across most of the porch can cross the 100-square-foot line. A rotten post, a soft sill or joists that have gone at the ends are framing, and framing replacement is on the permit list. Swapping a post is also a job where the roof has to be held up on temporary supports while the old post comes out, which is one more reason it is not handled like a screen repair.
For anything near the front of the house, Metro’s Front Porch Addition page sends questions to the Zoning Help Desk and the building division at 615-862-6550. Outside Davidson County, Williamson, Rutherford, Wilson and Sumner counties and their cities each run their own codes offices with their own rules, so the call is to that office, not Metro. We cover the permit process itself in our post on deck permits in Nashville, and the Nashville page lists the offices we work with.
Repairing it so it does not come back
Replacing a rotten rail with the same board in the same spot puts new wood back into the same wet corner. When we rebuild the bottom of a screen wall, the aim is to keep water and debris from sitting against the wood: a rail detail that lets the floor shed water past it rather than into it, a kick panel that can be wiped down, and treated lumber suited to where it sits. On the floor, the gaps between boards have to stay open so water drains through, and they have to be cleaned out once the leaves are down.
Paint and caulk are not a repair for soft wood. Filling a rotten rail and painting over it looks finished for a summer and hides the decay while it keeps going. If the screwdriver sinks in, the wood comes out. Floor boards, rails and stairs on a porch are the same work we do under deck repair, and on a porch they come with the added step of setting the screens back in tight once the wood is right.
The upkeep that keeps a porch out of this list is short: blow the leaves and pollen off the floor and away from the screen line through the fall and spring, keep furniture and rugs off the edges so the boards dry, clean the gutters so the roof does not dump water at the door, and push a screwdriver into the post bases once a year. If something there is already soft, ask us for a free written estimate and we will tell you whether it is a screen job or a wood job before anything is torn out.
Sources
- Metro Nashville Codes, Add Deck — Permit for board replacement over 100 sq ft, for any footing or framing replacement, and for replacing a deck; none for tearing down without replacing
- Metro Nashville Codes, Front Porch Addition — Questions to the Zoning Help Desk and the building division, 615-862-6550
- USDA Forest Service, Forest Products Laboratory, Wood Handbook, Chapter 14: Biodeterioration of Wood (FPL-GTR-282) — Decay, molds and stains come from fungi needing food, suitable temperature, moisture and oxygen; protection matters where conditions favor growth