Old House Remodeling:
Replacing A Window -
Installing An Andersen 400 Series
The window is placed in the
opening, adjusted until level, plumb and square, and nailed.
The trim is installed over the nailing flange, then caulked
3-4 (Intermediate - Advanced)
Bruce W. Maki,
Finally - Installing The Window !
The window we installed was an Andersen Tilt-Wash 400 Series
double-hung vinyl-clad wood window. It measured about 30" wide and
Before setting the window in the opening, we applied a bead of
siliconized acrylic latex caulk around the perimeter of the
rough opening. This was basically a futile procedure because the
sheathing on this old house was made from 1x10 boards and there were
substantial gaps everywhere.
With old houses like this it can be very difficult to keep water
out of window and door openings because the siding and sheathing
have so many gaps. Careful caulking of the final trim and siding are
The window was set in the opening and adjusted so that the
distance from window to the edge of the siding was the same
on both left and right sides. Then one nail was driven in at
a top corner (red arrow).
The sides were checked for plumb.
Please forgive us for cheating!!! We installed the window
completely and then went back to snap some pictures that roughly
depict the installation process. We did not have enough people on
this job to shoot photos and install the window at the same
The top and bottom were checked for level.
The diagonals were measured and compared.
Making sure the window is square is probably the single most
important step in window installation. An out-of-square window may
not open properly and may not seal properly.
Once the window was square, we drove in nails (1-3/4"
galvanized roofing nails) every 6" to 8".
The recommended nail spacing ends up using every other hole
in the nailing strip.
The actual window installation procedure took about 15 minutes.
The vast majority of the time on this, and most similar jobs, is
devoted to preparing the window opening and completing the trim.
We omitted the nailing flange at the bottom. Instead, the
window rested on the original sill. We placed a heavy bead
of caulk along this joint to ensure a good seal.
We slid a strip of blue foam sill-seal insulation under the
edge of the siding.
After the sides, we applied the same
material to the top.
Why the strips of foam? Because the nailing flanges of the
new construction window create an uneven surface for the
trim. The foam is compressible and will squish down when the
trim is nailed back in place, and the trim should sit flat.
Foam For Window Flashing? Are We Crazy?
Maybe not. When we replaced this window in 1999,
window flashing product such as Vycor were not widely
available. I have seen several houses where carpenters
used strips of tar paper for flashing around the nailing
flanges of windows. And I've seen many more houses where
no flashing was applied over the nailing flanges. The
caulking behind the nailing flanges is supposed to keep
water out, but that doesn't always work because caulk
gets smeared, or there are gaps in the wood sheathing.
The Preferred Flashing Method:
another article, shows a better method of flashing
around a new window. Grace Vycor rubberized asphalt membrane
is applied along the bottom flange (if applicable), then the
sides, and then the top flange. The membrane overlaps the
tar paper or housewrap, and if any water gets past the
siding, it should be directed downward and be kept away from
the wood structure.
The top section of trim was installed. The board had to be
notched to fit around the window frame.
Getting the board to slide under the awning brackets was
quite a feat.
Next, the side trim pieces were installed, after being ripped to
a slightly narrower width.
When the trim was installed, we caulked all gaps
- Between the window vinyl-clad frame and the window trim.
- Between the window trim and the clapboard siding.
- Between the window trim and the awning support brackets.
- Any place where rain could get behind the siding.
During these tasks the sun went down, so we were unable to take
The next day we painted the trim and the siding next to the
The ladders and extension plank, along with the awning
above the window, seemed to make a good support for a tarp.
The weather in October can get quite chilly here, too cold
for latex paint to dry properly.
So we hung a tarp over the work area and painted all around
the window with a good quality exterior paint.
By simply opening the window just installed, and firing up a
small kerosene heater in the room, the temperature under the tarp
quickly climbed to around 75 degrees, even though outside it was
struggling to make 50 !
After the paint had dried...
...everything looked so much better.
The completed window, with the screen installed.
Compare the new, second-story window with the century-old
unit directly below. The most noticeable difference is
caused by the screen on the new window.
The view out of the new window is much better, much
clearer, than the old window. And the new window does
not rattle in the breeze or let the cold wind pass through.
A serious and lasting improvement that maintains the
house's original design intention without sacrificing
comfort, convenience, or energy efficiency.
Back To Top
- Basic Carpentry Tools
- Reciprocating Saw
- Table Saw
- Belt Sander
- Extension Ladders (2)
- Ladder Jacks (2)
- Extension Plank
- Andersen 400 Series
Tilt-Wash Double-Hung Window
- 2" Roofing Nails
- Flashing Material