Buying a house with sash windows?

Double hung timber sash windows look great on older or period homes, but they can be draughty and offer poor thermal performance, assuming you want to keep them and not replace them with modern double glazed units (we wouldn’t unless they look the part!). Then there are a number of things to keep your eyes open for when you are viewing. There are many defects that will reduce the life and performance of the window and require expenditure to correct.

Image of sash window in need of repair

Here we show you how to recognise them.

Are there sash cords?

You need to check the sash cords are present. If they are, pull them without opening the window – you should feel the weight on the end. If you don’t, or the cord comes loose, then the sash cord needs replacing. It’s not a difficult job, but is fiddly and does need the access slip to be opened and possibly the sash to be removed, which may need the closing beads to be taken off and then re-fixed. Windows usually need redecorating at least in part after this work.

Open the window

Open the sash window and check it stays up. If it slips down it has probably been re-glazed with a thicker glass which is heavier than the original. If the original sash weight has been used, it may not be heavy enough to counter balance the window.

Signs of condensation

Have a look for the tell-tale signs of condensation. Because these windows are single glazed, they very often suffer more than double glazed and modern units.

The ironmongery

Check that all the ironmongery is present and that the sash hasn’t been painted shut and is free running. Quite often everything goes out of square when windows are badly maintained and this can affect catches. We’ve seen them adjusted with lolly sticks, cardboard and all manner of Heath Robinson solutions.

Remember that ground floor windows and other accessible windows almost certainly need key operated locks to comply with most insurers’ minimum requirements. Not a difficult or expensive job in itself, say £60 a window, but if you have 10 windows, then that cost mounts up.

Exterior frame and sill

Outside, have a look at the frame and the sill. If it’s badly maintained you may well see some decay. A key or screwdriver can be useful to jab into soft timber. This will probably be wet rot and will need cutting out and replacing. Look also for pieces of timber scarfed in and for metal ‘L’ brackets on the corners of sashes. These are all indicators that the units may be past their best and may need expensive attention.

Check the glazing

Look for any glazing below 600mm. These days, there should be safety or toughened glass, but this wasn’t the case 100 years ago. We strongly recommend adding fall protection or changing the glass. (see above as the sash weights may need to be hanged).

Check that the glass isn’t cracked. If it is, it may need replacing. Check that all the putty is OK, repairs here may mean external decoration.

Double or single glazed requirements

And finally, If the windows need replacing then current building regulations require them to be double glazed. This can be done to new sash units, but they will be thicker than the originals and probably stick out into the room by about 30mm. There’s not a lot than can be done to overcome this. The modern units though will look appropriate, be thermally efficient and have proper draught exclusion. Budget around £800 per window, on average, for a double glazed double inbox sash with hardwood sill. It’ll go up and up depending on size and location.

Conservation area?

Remember if your home is in a conservation area, or listed you should consult the conservation officer and planning department at the local authority as planning consent may be required. (You can read more about conservation areas in a previous blog we published – An introduction to conservation areas.)

More advice

Need more advice, a building or property survey or windows reported on? Collier Stevens can help across London and the South East.

(Originally published by Steve Way, 22 January 2012)