Double-hung, Double-Paned Windows From Scratch - Part 1

A few people have asked for more details on how I build my windows, so I've written up a step-by-step walkthrough of how I do it.  It seems daunting, but once you've built the first couple and get more comfortable, it really goes pretty smoothly.

First, think about the basic parts that make up a double-hung, double-paned window.  Structurally, it's very simple:

That's it - 14 pieces of wood (13 if you build the lower sash single-paned).  There's not a lot of complexity here.

I know that I'll be building a lot of these windows, so I keep a ready supply of these pieces pre-cut.  I recommend using a tool like The Chopper, it's really the only way to be sure you're cutting your pieces to exactly the same length each time.

I also recommend that you pre-paint your lumber before assembling the windows.  I've done it both ways, painting before assembly and after - it's much easier to paint them before.  The easiest way I've found to paint them is to stick all to the sticky side of a lint-roller sheet.  Paint one side, let it dry, then carefully remove the pieces from the sticky sheet (I use a razor blade to "scrape" them off), flip them over and paint the other side.

The hardest part about this whole process is keeping things square as you assemble the windows.  It could probably be made much simpler by building a jig, but to be honest, I don't know how to build a jig for this, so I've never tried.  I've had good luck with my method, so I've stuck with it.

You'll need a good pair of precision tweezers, a smooth, solid work surface (a glass tile, for example), and good glue.

Again, the hardest part about this is keeping the corners square.  You'll need a solid 90-degree corner for this - I use a couple of "1-2-3" machinist's blocks.  Start with the long side (piece A from the diagram above), place it on-edge against one side of your 90-degree corner.

Place a TINY bit of glue onto the end of a short side (piece B), barely enough to see.  Position the piece firmly against the longer piece, and square it up with the corner of a metal ruler or square.

Let this sit for a few minutes to allow the glue to take hold, then proceed with the other long side (piece A).  Place a tiny drop of glue to the inside piece, near the end, and position it against the end of the short piece that was just added.  Square it up with a ruler or square.  It's OK if the two side pieces angle slightly inward, in fact it can make it easier to put the fourth piece in place.

For the fourth piece, use another "B" piece.  Put a tiny bit of glue on each end and position the piece between the two sides of the sash frame.  Use your ruler or square to make sure it's positioned properly.

If you're building single-paned windows, you're done with this first sash.  If you're building double-paned windows, there's one more piece to install - the short center piece (piece C).  Put a TINY, and I emphasize TINY, bit of glue on each end of the center piece, and drop it into the sash frame, centered along the two short sides.  You could measure and mark the center, but I just eyeball it.

You've finished the first window sash.  For a double-hung window, you need two sashes, so just repeat these steps to build the second one.

In my next post, I'll show you how I add the glass window panes and how I build the frame around the window.  Stay tuned!