Replacing Windows and James Hardie Siding Together
If both are on your list, the order matters. Getting it wrong costs money and leaves weak points in the wall.
The right order
Windows first, then siding. Or both in one coordinated project. A window is sealed to the wall at its edges, and that seal is tied into the weather barrier and flashing that sit behind the siding. With the siding off, all of that is exposed and can be done properly. With the siding on, it’s buried.
What goes wrong if siding comes first
Replacing windows after new siding means working around finished trim and cladding. The installer either squeezes a new window into the old frame from inside, which limits the improvement, or cuts back the new siding and trim to reach the opening and then patches it. You pay for trim twice, and the patched area never looks quite as good as the original work.
What doing them together allows
- Full-frame replacement. The whole old window comes out, so any rot in the opening is found and repaired.
- Proper flashing. Sill, sides and head are flashed in the right order and lapped into the weather barrier, so water that reaches the opening is directed out.
- Trim designed once. Window trim is sized to the new windows.
- Changes to openings. Making a window larger, smaller or moving it is far simpler when the wall is open.
- One round of disruption. One bin, one set of scaffolding, one clean-up.
Where water gets in
Most water damage in walls starts at windows. The corners of the sill and the top of the frame are the usual culprits. Over the head of each window there should be a metal flashing that sheds water outward, with a small gap between it and the siding above. That gap is left open on purpose. Filling it with caulking traps water instead of letting it drain.
If the windows are staying
Perfectly fine. Sound windows don’t need replacing just because the siding is. What should still happen is that the existing windows are properly integrated: the opening flashed as well as the existing window allows, new trim fitted, and fresh sealant applied. Ask how this will be done on your house.
If you can only afford one now
Generally do the windows first and the siding when you can. If the siding can’t wait, because of hail damage for example, tell your siding installer that windows will follow. They may be able to detail the trim so it can be removed and refitted with less damage later. It won’t be as tidy as doing both together, but it helps.
Doors, too
The same logic applies to exterior doors and patio doors. They’re flashed and trimmed the same way. If one is due for replacement, do it before or with the siding.
Colour coordination
New windows usually mean choosing a frame colour. Decide it alongside the siding and trim. Black or dark frames with light siding, white frames with any colour, and frames matched to the trim are all common. See colour combinations.
One contractor or two?
Either can work. What matters is that someone is responsible for the joint between window and wall. When two companies each assume the other handled the flashing, nobody did. Raico Roofing and Exteriors can coordinate the exterior work so that responsibility is clear. Request an estimate.