Most exterior leaks don’t start in the middle of a wall. They start at the edges, where two parts of the house meet: the roof edge and the fascia, a window and the siding around it, or the bottom of a wall and a deck.
Those edges are where one trade’s work ends and another’s begins. If three companies work on your house, you’ve got a lot of edges. And often, nobody is in charge of them.
Why the seams are the weak spot
Each trade usually does its own part well enough. The roofer finishes the roof, the window installer seals the window, and the siding crew hangs boards right up to the trim. But water doesn’t care whose part it is. It runs down the wall and finds the first place where two jobs don’t overlap the right way.
Here’s a common one. The wrap at the top of a window ends up behind the window’s flange instead of lapped over it. Water running down the wrap slips behind the flange and into the wall. Each trade can say its own work was fine, and the wall still rots.
The order that keeps water moving out
When the roof, siding and windows are all due, the order matters. On most projects it goes like this:
- Fascia first, if the boards at the roof edge are soft, so the roofer has solid wood to work to.
- The new roof next.
- Windows once the old siding is off, and before the new siding goes up.
- Siding and trim after that.
- Gutters back on last.
Get the order wrong and someone ends up cutting into finished work, or sealing over a joint they can’t see behind.
One crew for the parts that touch the wall
That’s why some homeowners hand all the wall work to one company. Mi Casa Exteriors handles its exterior renovation work around Surrey this way. Its own crews do the siding, trim, fascia, soffit and the rot repair behind them, with no subcontractors. Windows are only replaced when the siding is already off. Roofing, gutters and insulation go to other trades, and the schedule is planned around them.
Fewer handoffs means fewer unprotected edges and less confusion about responsibility. If a joint the crew built leaks, there’s no question about who comes back.
What to ask before anyone starts
- Who’s responsible for each joint where your work meets someone else’s?
- What order will the trades come in, and who checks each handoff?
- If a joint leaks next winter, who comes back to fix it?
Get those answers in writing, because vague answers at the beginning usually become finger-pointing after the first heavy rain.
The idea behind it
Building scientists explain it simply. The water-resistant layer behind your siding only works if it’s continuous. It has to tie into the roof, the windows and the foundation, with each piece lapped like shingles so water always runs out. This drainage plane guide from Building Science Corporation shows how those pieces fit together.
You don’t need to learn flashing details yourself. You just need a clear answer to one question: who owns each joint? Settle that before the first trade shows up, and the rest gets a lot easier.
