Restoring a Double Hung Window

After doing a complete rebuild of the “worst” window in my house, I moved on to one of the “better” windows.  This smaller 6 over 6 had some rot in the corner of the bottom rail, many coats of old peeling paint, and a worn out frame complete with rusting lintel.  I decided to refurbish it instead of rebuilding it.  Step one was to remove all the interior molding, take the sashes out, remove the frame, and pop out the window sill.  This left me with my favorite plywood window and a 2×6 temporary sill:)

The next step is to remove all of the old paint.  My father-in-law experimented with numerous methods and settled on using a heat gun and paint scraper.  We are considering building / buying one of those heated paint removers for the next window.  The jawhorse is also indispensable for holding the moldings as you scrape.

Once everything was down to the bare wood, the damage could be assessed.  We ended up just cutting our the damaged part of the window sash and splicing in a piece of the bottom rail from the old window I removed in the dining room.  This way the molding profiles match nicely.  Everything was joined together with lap joints and dowels for strength.  All other repairs in the sash and frame were don’t with epoxy and wood patches.  After a good sanding and priming, it all looked good as new!

One interesting point in these windows is the outer sill.  The original design has a relatively flat sill profile which I attribute the rotting problem to.  We wanted to increase that angle, so we simply jigged the sill to my table saw fence “on end” and then cut a new angle into the first 6 inches of the sill.  This leaves you with a small ridge halfway into the sill, but I think it actually looks good, and the water runoff is certainly improved.

Lastly, there is no reason to restore brick mold.  This stuff had so much caulk, paint, and who knows what else attached to it that I just directed it straight to the garbage.  New brick mold is quite easy to make and I do it in bulk.  Just rip a long board down to strips wide enough for the mold profile you want.  Route a bead or whatever profile you desire, and then back bevel the brick side to account for unevenness in the brick surface.  

Here is the sill and mold primed.

The final step is to glaze the windows.  A few comments: (1) USE OLD GLASS.  New glass is painfully obvious from the street, and old glass is really easy to come by.  We get ours out of old sashes at the local Habitat for Humanity.  (2) Get a good putty knife.  Glazing putty is difficult enough to work with and having a nice knife helps.  (3) Don’t be discouraged.  The first panes of glass took me forever, but by the end, I could fly through in entire sash in maybe 40 minutes.  The basic process goes like this:

Cut your glass to fit using a glass cutter.  Loose is better – don’t try to force the glass or it WILL crack.  Put a bead of silicone on the muntin profile for the glass to sit in and bed it down snugly.  More silicone is better as you can trim it with a razor once it dries.  Press glazing points into the muntins to secure the glass.  Eventually I’d like to get a point gun for this, but now, I’m just using an old chisel.

Get glazing putty (DAP 33 linseed based) onto all of your joints.  Don’t bother with rolling it into “snakes”, just grab a ball of it and press it in using rubber gloves.  I work with the window on a flat surface, some people prefer vertical.  Now take your knife and cut into a corner at 45 degrees.  Draw the knife back so that the tip is INSIDE of the inner muntin profile.  You don’t want to see the glazing putty from inside the house.  The counter intuitive thing here is to keep a steep knife angle.  If you go shallow, the putty will jamb up behind the knife and pull it out of the joint.  With a steep angle, the knife cuts through the putty.  I’ll have to post a video of this step.

Any little imperfections you can also go back and smooth with your finger.  Set the glazed sashes aside and let dry AT LEAST TWO WEEKS.  People claim that they dry faster outside.  In any case, it takes a long time to firm up.  Once it has skinned over, you can prime and paint.  On this window, I tried masking the glass using the green painters tape.  You want to make sure that some of the paint gets on the glass since this forms the weather seal.  Use an oil based primer and a nice exterior paint.  Here are some shots of the finished sash.

Last step – reinstall the window.  This is largely the same as the first window I did.  Strip the lintel with angel grinder, rust convert with naval jelly, prime, paint.  Shim and sill into place with caulk for sealing.  Secure to the house framing.  Install the window frame to the rabbets in the sill.  Add mortar anyplace where there is damage to the brick.  Install the brick mold.  Prime and paint everything with exterior paint.  Install the sash pulleys, sash weights, copper chain, bronze weather stripping, and then the sashes.  Parting strips, interior molding, interior sill, and stool are last.  Here is the finished product.  Notice the window to the left which is a good comparison point.