There are two honest ways to put a new window in an old opening. The right one depends on the frame that is already there, not on a sales package.
Insert, or pocket, replacement
The old sash comes out. The existing frame stays. A new window is built to sit inside that frame.
Choose this when:
- The frame is solid, square, and dry
- Exterior trim and siding are worth keeping
- You want less disruption inside the rooms
Watch-outs: you give up a little glass area, and any rot hiding in that old frame stays hidden. If we see soft wood or a racked opening, we will not force an insert.
Full-frame replacement
The entire old window comes out to the rough opening. We flash the opening, set a new unit, and close the interior and exterior finishes back up.
Choose this when:
- The frame is rotten, out of square, or aluminum that has had it
- You want to change the look of the exterior casing
- Water has already been in the wall
It is more work. It is also the only way to start over at the opening — which is what a wet Washington wall often needs.
Signs a frame won’t take an insert
An insert only works if the existing frame is doing its job structurally. Walk the opening and check for:
- Soft wood at the sill or jamb — press with a screwdriver handle, not just a look. If it gives, water has been inside the wall.
- A sash that racks instead of sliding square — the opening itself has shifted, not just the hardware.
- Visible gap or daylight at a corner — the frame is no longer square enough to seal a new insert against.
- Aluminum frames with heavy pitting or corrosion — common on 1970s-80s Vancouver-area homes, and rarely worth insetting into.
Any one of these usually means full-frame, whatever the rest of the house gets.
How we decide on site
We do not pick a method from a photo of the glass. We look at:
- The sill and stool with a probe, not just an eye
- Whether the sash still closes square
- How the exterior cladding meets the old casing
- Whether you want the same sightlines or a different window style
Then the estimate lists the method per opening, not one price that hides a worse job.
What this means for cost and time
Inserts are usually faster and cost less per opening. Full-frame takes more crew time and more finish work. A mixed house is normal. Read what a Washington project costs for ranges, then get a measure so the number is about your openings.
- Sill pan firstA pan or pan flashing goes in before the window, sloped out, with the back dam turned up.
- Window set into the panShimmed plumb and square, fins landing flat on the sheathing. Never caulk the sill fin closed.
- Jamb flashing over the finsSides go on next, lapping over the sill flashing so any water is handed downward.
- Head flashing lastThe head laps over the jambs, and the housewrap laps over the head. Shingle order, top over bottom.
Common questions
Is insert replacement cheaper?
Often, yes. You keep the existing frame, so there is less siding and interior finish work. It is only cheaper if that frame is still sound and square.
Will an insert make the glass smaller?
A little. The new frame sits inside the old one, so you lose a strip of glass around the edge. On most houses it is hard to notice. On a small bathroom window it can matter.
Can you mix methods on one house?
Yes. A rotten kitchen sink window may need full-frame while the bedrooms take inserts. The elevations should still read as one house.