How to Repair a Wooden Window Sash

Wood win­dows add a clas­sic aes­thet­ic to your home. Prop­er­ly main­tained, they can look great for years. You can paint them one col­or, and years down the line, repaint to match any changes to your home’s exte­ri­or and inte­ri­or, giv­ing you more flex­i­bil­i­ty than you would have with oth­er mate­ri­als, like vinyl.

But even­tu­al­ly, wood win­dow sash­es may become dam­aged or degrade, espe­cial­ly in old­er, his­toric homes. As a nat­ur­al mate­r­i­al exposed to the ele­ments, over time your win­dow sash­es can chip and even­tu­al­ly rot, even with reg­u­lar main­te­nance. Sash win­dow repair involves atten­tion to detail, but it is some­thing you can man­age on your own with patience and knowledge.

If you’re active in inspect­ing and keep­ing your win­dow sash­es look­ing good, it’s pos­si­ble that all you’ll need is a few spot repairs to fix chips and splits in the wood. You can repair these sur­face issues with a sash repair kit. These sash win­dow repairs will also keep out water and pests that can lead to more rot. 

If, how­ev­er, you don’t check your wood win­dow sash­es for dam­age reg­u­lar­ly, rot can set in, which will then require a full or par­tial wood win­dow sash replacement.

Depend­ing on the extent of your sash win­dow repair, you may be able to get it done with­out remov­ing the panes from the sash. If you’re only patch­ing a small crack in the sash, you may be able to sand it, fill it in with epoxy, sand some more and paint.

If, how­ev­er, the dam­age is more exten­sive, you may need to take the whole assem­bly apart to repair or replace win­dow parts.

Below are the steps to replac­ing an old-style wood win­dow sash, the kind that is typ­i­cal­ly seen in homes pre-1970s. While we under­stand you may want to stay true to your old­er home’s win­dows, it’s impor­tant to real­ize that they could be cost­ing you mon­ey on your ener­gy bills. Old win­dows, even ones well main­tained or recent­ly repaired, don’t fea­ture the same ener­gy effi­cien­cy and func­tion as new­er windows. 

If you want to save mon­ey on your ener­gy bill and avoid the has­sle of con­tin­u­ous­ly repair­ing your win­dow sash­es, you should con­sid­er replac­ing the entire win­dow. Com­pa­nies like Fen­ster USA offer a wide vari­ety of wood­en win­dows, so you are sure to be able to find a new win­dow in the same style as your old win­dow. You’ll get all the beau­ty of your old style with all the ben­e­fits of mod­ern win­dow technology.

If you’re remov­ing parts of the wood­en win­dow sash, you’ll need to take the sash out from the frame. To do so, unscrew the stops, which are the two blocks that keep the low­er sash from slid­ing up too high, or part­ing beads, which hold the upper sash in place. Remove any cords or chains and tie them off to keep them from retract­ing if they’re weighted.

Glass panes in a wood win­dow sash are held in place with glaz­ing com­pound or put­ty. While durable, glaz­ing com­pound will crack and split over time. To release the glass from the sash, you’ll need a heat gun and chis­el. Gen­tly heat the glaz­ing com­pound with the heat gun and then scrape it off with the chis­el, tak­ing care not to scratch the glass.

Once the glaz­ing com­pound has been removed, you can gen­tly pry off the glass. If you’re work­ing with more than one pane, make sure you label them so you know where they fit when you’re done with your repair.

If you’ve gone to the trou­ble of tak­ing the glass out of your sash, it’s a good idea to go ahead and do anoth­er thor­ough inspec­tion of the whole sash. You’ll be able to iden­ti­fy any pre­vi­ous­ly-hid­den places where the wood may have start­ed to rot or where old glue, weath­er strip­ping or hard­ware has also degrad­ed. While this may be an extra step, it will save you from hav­ing to do even more repairs in the future.

Clean out the joints to remove any crum­bling epoxy or rot­ting wood. Sand down any chipped areas. Pre­pare your fresh epoxy or wood filler accord­ing to the manufacturer’s spec­i­fi­ca­tions, and apply using a knife. Let it cure and sand down. 

OR

If you need to replace some or all of the sash, care­ful­ly take apart the old sash. Keep the exist­ing parts, as you’ll need them to mark where any hard­ware goes as you assem­ble the new wood win­dow parts.

Win­dow sash replace­ment kits can be pur­chased to make your win­dow repair project sim­pler. They are pre-cut to the dimen­sions of your exist­ing sash and can be built to match a num­ber of mod­els from old­er win­dow man­u­fac­tur­ers, so the joints and grooves will fit with your exist­ing parts if you aren’t replac­ing the entire sash.

Assem­ble your wood win­dow sash replace­ment. Make sure all your joints are flush and smooth so the panes will fit prop­er­ly and the com­plet­ed sash won’t catch on the tracks. Use the old­er sash parts you kept so you can mea­sure and mark the loca­tion of any hard­ware like hinges and screw them in place.

Prim­ing is an impor­tant step. Seal­ing the wood will pro­tect it for years and save you the work of hav­ing to do addi­tion­al repairs before you real­ly need to. Prim­ing also means the wood won’t suck nec­es­sary oils out of the glaz­ing com­pound, which could cause it to crack and fail prematurely.

Use glaz­ing com­pound to secure the glass back into place in the repaired sash. Don’t be afraid to be lib­er­al with the com­pound; you’ll wind up cut­ting most it off, but you want to make sure it’s been ful­ly and even­ly applied to the sash rab­bet. Gen­tly press the glass in place to make sure the sash is filled, and then cut away the excess compound.

Points are set into the reassem­bled sash to ful­ly hold the panes in place. They can be applied with a gun or by hand. Depend­ing on the size of your panes, you may need more than one on each side. Points should not be more than 10 – 12 inch­es apart.

Apply anoth­er lay­er of put­ty on the sash and out­side of the glass. Don’t wor­ry too much about mak­ing it look clean at first; the goal is sim­ply to apply an even lay­er all the way around the pane. Pack the put­ty into place with the edge of the knife. Apply a sec­ond lay­er, and use the knife blade to cre­ate a smooth and thin bev­el all the way around. Let it cure ful­ly before painting.

Once your win­dow repairs and replace­ment parts are ful­ly cured, you can paint and stain as desired to match your home’s inte­ri­or and exterior.

Before you rehang your repaired wood win­dow, add weath­er­strip­ping or replace old weath­er­strip­ping. This pro­tects your home and your win­dow. Lubri­cate the tracks. Reat­tach cords or chains and slide the sash back into place. Replace stops and part­ing beads.

Repair­ing a wood win­dow sash sounds com­pli­cat­ed, but the actu­al step-by-step process is not over­ly com­plex. With the right wood win­dow replace­ment parts and a lit­tle patience, you can repair your own win­dows and have them back in place in no time. 

Or, if you want to save your­self the has­sle and get more ener­gy effi­cient win­dows in the style you want, vis­it the ReWin­dow web­site to explore our line of wood windows.