A pergola tied into the side of a Ladue house looks like a patio project, but once its beams are fixed to the wall it becomes part of the roof system. The beams carry snow and wind into the house, they put fasteners through the fascia or the rafter tails, and they often shed rain onto the same gutter line the roofer is about to replace. A homeowner who orders a new roof and a new pergola in the same season should expect one contractor to see both, because the attachment point is where the two jobs meet.
Why the attachment is a roof detail
Most attached pergolas in this area are fixed to a ledger board, a row of brackets, or the fascia itself. Each choice puts a different load on the structure behind it. A ledger bolted into brick veneer depends on the wall ties and the rim joist. A bracket screwed through fascia depends on whether that fascia is sound wood or a board that has been softened by years of water running off a gutter that was never quite level. The roof edge is what you are replacing, so the wrong attachment can undo the new drip edge and underlayment within a season of the crew leaving.
The freeze and thaw cycle in St. Louis makes this worse than it looks on a drawing. Water gets into a fastener hole, freezes in January, and widens the hole by spring. A pergola beam that sits in a shallow pocket of standing water will push that water into the joint every time it rains. None of this is dramatic on the day the pergola goes up. It shows up two or three winters later as a stain on the soffit or a soft spot at the bracket.
Where the posts land
Freestanding posts are the cleaner choice when the lot allows them, because they do not load the house at all. Ladue lots often have the room for that, especially on the rear and side yards of larger houses set back from the road. When the posts stand on their own footings and the beams only rest on them, the roofer has nothing to flash and the existing roof edge stays a roof edge.
When the pergola has to be attached, ask the roofer and the pergola builder to agree on where the attachment sits before any work starts. Attaching at the top of a wall that has a window, a hose bib or an exterior light fixture means that someone will be cutting through a detail that the other trade expected to find intact. Houses with heavy stone or brick often have a band course or a water table where a pergola would naturally meet the wall, and that is a place where water tends to stand.
Flashing at the ledger and the bracket
Any fastener that goes through a wall, fascia or roof edge needs flashing above it, or it needs a sealant product rated for that surface. Caulk alone is not a flashing. The usual sequence is that the roofer runs the drip edge and the underlayment first, then the pergola builder fixes the ledger or the brackets, then the flashing goes over the top of the ledger or behind the bracket so water sheds outward. If the order is reversed, the flashing ends up trapped beneath the new drip edge, and the water it was meant to shed runs behind the shingles.
Ask who installs the flashing and who is responsible for it if a leak appears. A written scope from the roofer should say whether the roof edge at the pergola attachment is included, and whether the pergola builder's work is included in the same price or sits under a separate contract. Two contracts can leave a gap at exactly the spot where the water comes in.
Rafter tails, fascia and the load you are adding
The rafter tails under a fascia board carry the roof edge. If a pergola beam is fastened into the fascia and the fascia is only nailed to rotten tails, the beam can pull the whole edge down over several seasons. Before the new roof goes on, the roofer should check the tails that will sit under the pergola attachment. If any are soft, the repair belongs in the roof quote, because it is a condition of the roof edge, not a feature of the pergola.
Snow is the load most people forget. A pergola with a solid top or a dense vine can hold a foot of wet snow on a winter afternoon, and that weight travels into the fascia and the wall. Ask the pergola builder what the design load is, and ask the roofer whether the rafter size and the fascia size can carry it. Neither one can answer the other's question, which is why the two should be asked in the same meeting.
Gutters and the drip line
A pergola roof sheds rain, and it sheds it somewhere. If that water falls onto the gutter, the gutter has to take it, and the downspout has to carry it away from the foundation. If it falls beside the gutter, it can splash back onto the fascia and wear the paint. Either way the gutter line is affected, so the gutter detail should appear in the same quote as the roof edge. A pergola that drains into a short run of gutter on a long roof can overwhelm one section during a heavy storm, and that section will be the first to overflow.
Where the pergola sits above a patio, the drip line from its top matters too. Water falling from the edge of a pergola onto a paver walk can freeze in winter and turn the walk into a hazard. A short run of gutter or a downspout routed away from the walk is cheaper to plan now than to add after the first icy week.
What to ask for in the quote
A roof quote that touches the pergola attachment should name the attachment points, the flashing method, the fascia or rafter tail repairs, and the gutter changes in writing. It should say whether the pergola builder's work is included, excluded, or left for a separate contract. If any of those lines are missing, ask the roofer to add them before you sign, because the crew that opens the roof is usually not the crew that comes back for the flashing.
Ask for photographs of the attachment area before the tear-off starts. The photographs should show the wall, the fascia, the existing gutter hangers and the pergola posts or brackets as they stand. If something is loose or soft in those photographs, you have a record of its condition before any work begins. Keys Roofing puts a written scope with photos and measurements in the homeowner's hands at the start of the job, and that is the place to ask for the attachment detail to be recorded as its own item. The office line is (314) 220-2333.
Permits and the Ladue building department
A pergola attached to the house usually needs a building permit, and the roof work usually needs one too. Ladue handles these through its building department, and the pergola and the roof may be reviewed separately even when they share a wall. Ask the building department which permits apply to each job before anyone pulls the first nail. Do not assume the roofer's permit covers the pergola, and do not assume the pergola builder's permit covers the roof edge.
Missouri does not license roofers at the state level, so the permit file and the written scope are the records that show what was done. Keep copies of both. If an inspector asks about the attachment, the scope and the photographs answer the question faster than memory does.
The order of work that keeps the edge dry
Settle the attachment before the tear-off, not after. Walk the wall with the roofer and the pergola builder together. Mark the fascia and the wall where the ledger or brackets will go, and confirm that the flashing will be installed in the sequence the roofer uses. Then let the roof go on, let the flashing go over the top of the attachment, and let the pergola go up last, with the gutter detail confirmed as installed. The order matters because each step changes the surface the next step has to seal.