Replicating Historic Wood Window Sash

Reproducing true double hung windows from an old house is tricky, but it's a worthwhile challenge for a devoted woodworker. Here are tips on the methods and the pitfalls. August 15, 2012

I have an opportunity to replicate window sash from an 1810 house that we are restoring. I am great with making moulding, but have not tried my hand at sash making and could use some advice. Each sash has 6 true divided lights, and are 6 over 6 double hung units. I know that I am going to use brass weatherstrip and making the jams and sill is not an issue, but running the muttin stock on the shaper is my concern.

Forum Responses
(Architectural Woodworking Forum)
From contributor D:
Depending on how many you have to make, you can save yourself a lot of trouble and outsource them. A lot of learning curve is involved in double hungs. Several cutters are needed (check rail face, cope and tenon, profile, etc.), and if you don't have several shapers to dedicate to them, I can guarantee frustration when having to change your setups.

Still, just copying a few old sashes you have on the bench to refer to isn't that bad for a starter. Replicating a very large order with lots of different sizes is a different story. You'll want to run all your lineal stock at once, so all your bars are exactly the same. Otherwise when cutting to length and coping, things won't line up. A few bars run 1/32 small stack up when doing TDL work. Four parts 1/32 small potentially cause you to fit a sash together which is a whole 1/8" too small. Bars can be run which are trying to lay over, and look just fine, until you've run 500 feet of it and begin coping to find out the bar is a hair thicker on the top than the bottom. No go. Coping you will find to be off one side to the other in height when fitting your bars into your female chip backer, and whole assemblies will have joints all tight on one side and all gaps on the other. So throw all that out and start over - you see where this is going?

I'm not going to brag and say this is too difficult, because it's not. You just have to be meticulous and sometimes those deadlines can get pretty heavy if you've not done this day in and day out. Things like using a real tenoner instead of a mitersled in a shaper to do your copes will increase quality. Putty glazing done in this era is also an issue and a dying skill - there's no magic tool here except hand skill. You might get good at it after the first fifty if you are a fast learner. I've seen many millwork guys come and go over the years, but the proficient putty glazers who can do beautiful work number less than ten. If after an hour you still have one buggered up looking putty glaze you've scraped out three times, you know it's going to be a long day...

From contributor H:
Contributor D sounds a reasonable note of caution, but if you outsource every new type of work, you will never progress. We build quite a lot of sash windows and I haven't encountered the problems that contributor D recites.

We are building 14 TDL windows 4 1/2 feet by 20 feet for a church. I would describe window work as exacting. If you have equipment that can reliably produce parts to specification, then you should have no problem. It helps to have a precise mind.

Create a good drawing (I use Google Sketchup). Think about a prototype in poplar. Better to make your mistakes in cheap wood. And finally, write down your construction process. I would encourage you to charge ahead.

From contributor E:
As a woodworker I prefer to invest in the machinery, tooling and educational resources (asking questions) rather than outsourcing. I have only 2 double hung windows to replicate. The owner would be happy outsourcing but I would rather attempt. Fortunately for me he is leaving for Europe and that gives me 10 days to recreate them. I ordered the cutters today from my supplier, so soon we will see.

From contributor B:
This can be a fairly simple project if you take the shortcut of not mortising each muntin end into the frame. It makes for a weaker sash but is a lot easier to construct. If on the other hand you plan to do a thorough reproduction, you will want to mortise those muntin ends to the frame. This will require a coping set that leaves the extra stock length required to create the tenon.

I agree that on a small order this is a great opportunity to hone existing skills and take them to the next level.