There are a lot of different techniques to weatherstrip wood windows. Like anything, some are more effective than others. In this post I’ll show you how to install spring bronze weatherstripping on your old windows.
Spring bronze is without a doubt my favorite type of weatherstripping for a few reasons:
- Very attractive and gains a nice patina as it ages
- Lasts well over 100 years when installed properly
- Very effective at air sealing
- Extremely adaptable to seal gaps of various sizes
Anything that lasts as long and works as well as spring bronze weatherstripping usually requires a bit more work to install than the peel and stick weatherstripping you find at the hardware store. Once it’s installed and tuned properly you can forget about it, and in our “no maintenance” culture today that is awesome!
- Tin Snips
- 1 3/8″ Spring Bronze
- Coppered Nails (if you live in coastal areas use solid bronze nails)
- Drill (with 5/64″ bit)
- Tape Measure
You can read my previous post about weatherstripping doors here: How To: Install Spring Bronze Weatherstripping
How To: Weatherstrip Wood Windows
You’ll need to have the sashes removed from the window jamb in order to install the spring bronze. We tend to install the weatherstripping as a part of a full restoration of the jambs and sashes.
If your windows are painted shut or can barely move due to paint build up, installing spring bronze won’t do much good other than to make them even more difficult to operate.
If this is the case, prior to installation scrape the jambs clean of the decades of paint build up so you have a smooth surface to work with. If you want your jambs primed (which I recommend) or painted you’ll need to do this prior to installation as well. Trying to paint around spring bronze is a pain in the @$#.
If you have restored, easily operable or even windows that are just loose in their jambs you are a good candidate for spring bronze weatherstripping.
Step #1 Cut to Length
Measure the height of the bottom sash. Using your tin snips cut two lengths (one for each side of the jamb). Cut them 1 1/2″ longer than the height of the bottom sash with a bevel at the bottom to match the sill angle.
For the top sash your measurements have to be a little different. Measure the height of the top sash, add 1 1/2″ then measure the distance from the top for he jamb to the bottom of the pulley (in the case of this picture 9″). Subtract the 9″ (or whatever your measurement is from the previous number and you’ll have the length of your bronze for the top sash.
ie. Top sash height = 32″ + 1 1/2″ – 9″ = 24 1/2″
I promise the math lesson is now over. Phew!
Step #2 Pre-drill & Nail
Caution!: Spring bronze is nailed over top of the weight pocket access doors. Once it is installed it will have to be removed is you ever need to access the weight pockets to re-rope your old windows.
If your jambs are very sturdy and the wood isn’t hard as a rock then you can just nail right through the bronze and into the wood. If this is the case you are a very lucky person.
I have only found one house that this worked on. The rest have had jambs that are made from petrified wood that is so poorly attached it bounces like a trampoline with every blow of my hammer. If this is the case you’ll need to pre-drill. Here’s how:
- Set your bronze in place on the jamb with the nail side (the flat side) facing inside the house. Make sure it is right in the middle of the jamb. There should be at least 1/16″ space between the bronze and the blind stop and parting bead to allow it to flex properly.
- Drill the first hole at the top thru the bronze and into the wood about a 1/2″. Tap in a coppered nail so it dimples the surface just a bit.
- Pull the bronze nice and tight and repeat the process about halfway down the length and again at the bottom. The second hole you pre-drill will set the angle of the bronze, so make sure it is lined up straight and doesn’t wander into the parting bead or blind stop at one end.
- Go back and repeat the process so that there is a nail every 1 1/2″ to 2″ along the length of the spring bronze.
Step #3 Spring the Bronze
Once it’s all nailed in place go back and spring the bronze if necessary to increase the amount of gap it will fill. Test fit your window first to see if you have a snug fit or if there are gaps where the bronze isn’t running against the side of the sash.
If there are gaps you need to bend the spring bronze out in those sections so that it puts light consistent pressure on the sides of the sash. To bend the bronze you can gently use a putty knife to bend it back.
Sometimes I have come across windows where the jambs are just too loose to nail anything. In these cases I have resorted to a pneumatic narrow crown stapler to install the bronze. I’m not going to lie, it goes MUCH faster! But there are a few things to be careful of if you decide to go this route.
- Use only 3/4″ stainless steel staples – Anything longer can get in the way of the moving weights behind the jamb. These nails will be exposed to the weather so if they aren’t stainless they will rust and loose their hold in a short time. Also, anytime you put two different types of metal together you run the risk of galvanic corrosion which causes the metals to rust and corrode prematurely. This shouldn’t be a problem with stainless steel because the coppered nails are steel in their core as well. But if you use something like aluminum nails you may have a problem.
- Turn the pressure down on your nailer. It is very easy to blow right through the thin bronze with an air nailer/stapler. Test a few strips to find the right air pressure and depth.
- Still put a nail at the top and bottom of the bronze. The coppered nails hold better than pneumatic staples will. The two spots that are most likely to pull away are the end of the bronze so put a nail in those spots to make sure it doesn’t pull away in the future.
There is also a strip of bronze that can be installed at the meeting rails between the two sashes, but I rarely use it since I have found that by simply adjusting the sash lock I can achieve a good enough seal to avoid this added expense.
Once your spring bronze is installed you won’t have the stereotypical drafty old house anymore. Enjoy the lower energy bills and warmer winters indoors!
You can find some more energy saving ideas for an old house here: 4 Cures For a Drafty Old House