Screened porches and covered decks

Three things make a covered structure more compelling here than it is further north. The sun is direct and hot for most of the year, so an open west-facing deck is unpleasant through the middle of the afternoon. The wet season runs through summer with thunderstorms on a near-daily rhythm, which takes a large share of the evenings the deck was built for. And a county with this much wetland and hammock ground has real insect pressure at dusk. Roof plus screen turns furniture that gets rained on into furniture that gets sat on.

A roof is a second structure, not an accessory

This is the part that surprises people when the quote arrives. A roof adds dead load onto the deck framing, which means the beams, posts, and footings under it are sized for the roof as well as the floor. It adds uplift, which is a wind question. And it usually means tying into the existing house roof, which is a flashing question.

The uplift is the part worth understanding, because it is not intuitive. A flat open deck close to the ground gives wind almost nothing to work with. Put a roof on it and you have made a wing: air moving across and under it wants to lift the whole thing, and what resists that is not the weight of the roof but the connections holding it to everything below.

Continuous load path

The phrase describes an unbroken chain of connections carrying load from the top of a structure to the ground: rafter to beam, beam to post, post to footing. In an uplift event that chain works in reverse, holding the roof down, and it is only as good as its weakest link. A well-framed roof on posts that are simply toe-nailed to a beam is a roof with a gap in its load path.

This is the main technical reason a covered deck costs more than the sum of a deck and a roof. Every connection in that chain is specified, and the footings at the bottom of it are larger.

Tying into the house roof

Where the new roof meets the existing one, the joint has to be flashed and shingled the way any roof-to-wall or roof-to-roof junction is, not sealed with a bead of caulk at the seam. Getting this wrong creates a leak in a house that did not have one, which is a considerably more expensive problem than the porch it came with.

The pitch of the new roof also has to work with the existing one and with the head height under it. A shallow pitch keeps the roof under the existing eave line but sheds water more slowly; a steeper pitch sheds better but can run into windows on the wall above. Working that out is design rather than assembly, and it is worth doing on paper.

Can a roof go over the deck I already have?

Only if the existing structure can carry it, and that gets established before anything is designed. A deck built to support people and furniture was not necessarily built to support a roof, the uplift on that roof, and the additional post loads that come with it. The check covers footing size, post size and spacing, beam capacity, and the condition of everything at grade.

Sometimes the answer is yes with additional footings and posts. Sometimes the honest answer is that rebuilding the frame costs less than reinforcing it, particularly on an older deck where the base of the posts is already suspect. A contractor who opens it up before answering is giving you a real answer.

Screen rooms fail at the edges

A screen enclosure that lets mosquitoes in is almost never failing at the mesh. It is failing around the door, at the base where the screen frame meets the deck, where the frame meets the house wall, or up at the roof line. Those are the details to care about.

Kickplates at the base are worth having. That lower band takes feet, pets, and debris thrown by a mower, and an unprotected screen there is the first panel to go. Heavier pet-resistant mesh in the lower panels is a common and sensible compromise, rather than running it across the whole enclosure at higher cost.

Door hardware matters more than people expect. A screen door that only latches when it is pulled is a screen room that is open half the time, and on a summer evening near Paynes Prairie or the lakes out toward Melrose that is the difference between using the room and abandoning it.

Ceiling fans, lights, and planning ahead

A fan does two useful things in a screened porch here: it moves air, which makes a humid evening noticeably more comfortable, and moving air discourages mosquitoes. Fan and light positions are worth deciding at framing stage so the blocking and the wiring route go in while the structure is open, rather than being retrofitted through a finished ceiling.

Where the new roof puts the water

A roof over a deck collects a surprising volume of water in a climate that delivers a storm most summer afternoons, and all of it comes off one edge. Left to run free it lands in a line along the outside of the deck, which is exactly where the outer posts and their footings are. Over a few wet seasons that washes soil away from around them and keeps the base of the structure damp year round.

The fix is ordinary and cheap if it is designed in: a gutter along the low edge, a downspout at each end, and the discharge taken away from the structure rather than dropped beside it. Retrofitting it after the fact is also possible, but by then you have usually had the erosion.

The pattern that works on most lots

A covered or screened section adjoining the house for the table and the seating, and open deck beyond it for the times people want sun. That gives you somewhere usable in July and somewhere pleasant in February, and it costs a good deal less than roofing the whole thing.