New window in old house. Old House Remodeling:

Replacing A Window - Part 2
Installing An Andersen 400 Series

In This Article:

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 and painted.

Related Articles:
Skill Level: 3-4 (Intermediate - Advanced) Time Taken: 12 Hours

By , Editor


View Part 1 - Preparing The Rough Opening.

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 64" tall.

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 necessary.

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 time.


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:

This window, from 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.

New window with self-stick flashing.


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 including:

  • 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 any photos.

The next day we painted the trim and the siding next to the window.


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.



Tools Used:

  • Basic Carpentry Tools
  • Reciprocating Saw
  • Table Saw
  • Belt Sander
  • Extension Ladders (2)
  • Ladder Jacks (2)
  • Extension Plank

Materials Used:

  • Andersen 400 Series Tilt-Wash Double-Hung Window
  • 2" Roofing Nails
  • Flashing Material


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Copyright © 1999-2009

Written October 10, 1999
Revised January 27, 2009