Sash window double glazing costs vary widely because the price depends on the size of your windows, how much rot or damage is present, and whether you need a full replacement or a repair. A window the size of a standard bedroom sash costs less than a large bay window. The only way to know what you will pay is to measure your windows and describe their condition to a tradesperson.
What moves the price up or down
Three things decide what sash window double glazing will cost you. First is size: a small sash window costs less than a large one because there is less glass, frame and labour. Second is what needs doing: if your window is sound and just needs new glass units, that costs less than replacing the whole frame because rot has set in. Third is the material. A new sash frame made from green oak costs more than one made from softwood, and hardwood veneers cost more still.
If your windows stick, rattle or let draught through, the fix might not be full replacement. A good tradesperson will look at whether the sash cords are worn, the weights are stuck, or the frame itself has twisted. These repairs cost less and keep the character of an older house. Full replacement is the choice when the wood is soft to the touch, water runs down the inside of the glass, or the frame is so bent that repairs will not hold.
What a careful buyer checks before calling
Measure your windows before you contact anyone. Note the height and width of the glass opening in each sash, and count how many panes you have. A window with twelve panes costs more to glaze than one with two because the frames are finer and the work is more detailed. Look at the frame and sill: is the wood soft when you press it with a fingernail, or is it hard and sound. Can you see where water has sat and stained or swollen the wood. Does the sash move freely or does it stick.
Take a photograph of the problem area if there is rot or damage. Write down whether you think you need the whole window replaced or just the glass units changed. This information lets a tradesperson give you a real estimate before the visit, so the price you are quoted is close to what you will pay.
Why transparency matters
A good tradesperson will give you a written estimate before the work starts, based on what you have told them and what they see on the day. The estimate should list what is being done, whether that is new glass, new cords, or a full frame, and what it costs. If the condition of the window is worse than expected when the tradesperson arrives, they should tell you and give you a revised price. A price that changes without explanation is a sign to ask questions.
Before you agree, ask what happens if the work finds something unexpected, such as decay that was hidden by paint. A clear answer shows you are dealing with someone who knows the trade and is honest about risk.
Getting a real quote
When you are ready to call a tradesperson, have your measurements and photographs to hand. Tell them the size of each window, what you see wrong with it, and whether you think it needs repair or replacement. Ask them how they work out the cost and how long it will take. A tradesperson who can give you a ballpark figure straightaway, based on what you describe, is more useful than one who books a visit without listening to you first.
Some tradespeople offer an online tool where you enter your window size and condition and get an estimated price. This is a help because it gives you a figure to expect before you talk to anyone. Colchester is one place where sash window work happens regularly, so if you are in the south east, you have choice among firms. Ask more than one for a quote so you can compare.