How Much Does it Cost to Replace a Window Sill in 2023?

Wooden window sills give a timeless look to a property, especially period homes. But they don't last forever – and when they become rotten, they could let rain into your home and cause damp.

It's important to get damaged window sills repaired or replaced as soon as possible – but how much does it cost to replace a window sill?

Window sill replacement and repair cost

How much it costs to replace or repair your window sill will depend on the size and type of window, the wood you choose and where you live. But here are the average costs to expect:

Job	Average cost
Window sill replacement (including labour & materials)	£140-£220
Severely rotten window sill replacement and frame (including labour & materials)	£300-£350
Sash window sill replacement (including labour & materials)	£120-£340
Bay window sill replacement (including labour & materials)	£170-£200
Door threshold repair	£60-£110
Carpenter hourly rate	£16-£40

These window sill repair and replacement prices are taken from averages across the entire UK. If you live in a major city or the south east, expect to pay more. If you live in more remote areas of the country, you may pay less for a carpenter.

HaMuch has a huge database of hourly and daily rates for carpenters all over the UK, so take a look at the table further down the page to find out how much to expect to pay for a carpenter in your area.

How much does it cost to replace rotten wood around a window?

If your wooden window frame is rotten as well as your window sill, this will drive up the cost of window sill replacement. Expect it to cost up to £350 to replace the rotten wood around a window and the window sill.

How do I know if my window sill is rotten?

You'll know if your window sill is rotten by the way it looks and feels. The signs of a rotten window sill are the same whether they are internal or external wooden window sills:

Look for peeling or cracked paint. If the paintwork is damaged, that usually means that water has penetrated the surface and therefore damaged the sill itself.

Check to see whether your window sill is spongy. If you press your window sill and it feels soft and springy, that means it's rotten.

Spot crumbliness or brittleness. Touch your window sill – does it crumble away under your fingers? That means it's definitely time to replace it.

How long does it take to replace a window sill?

For an average-sized window, it should only take a carpenter between 1-2 hours to replace your window sill. That's assuming that they are replacing a wooden window sill with another one – if they are replacing a window sill made from stone or concrete with a wooden one, it may take longer as it will be harder to remove the old one.

If you want to replace all the window sills in your home, expect it to take around 1-3 days. It will of course depend on the number of windows you have in your home and how big it is.

What kind of wood should you use to replace a window sill?

You'll want to use a hard-wearing wood that's been treated to give it water-resistant properties. Chestnut, mahogany, maple and oak are often used for wooden window sills.

To maximise the life of your window sills, you should maintain them regularly. Make sure you paint them with a good-quality gloss, satin or eggshell paint that is designed for wood. Brands like Dulux, Armstead or Johnstone's are good options and cost between £11-£25 per litre. If you want a decorator to paint your window sills for you, expect this to cost around £200 for around 4 window sills and frames in your home.

You could also stain your window sills to give them more water resistance. Ronseal, Dulux, Sadolin and Osmo are all good brands of woodstain for internal and external wooden window sills. Expect to pay between £10-£15 for a 250ml tin of woodstain.

Can you put new wood over rotten wood?

We wouldn't recommend putting new wood over rotten wood. If you try to put a new wooden window sill over a rotten one, it's likely that your new window sill will just end up rotting more quickly.

If your wood window sill isn't rotten in all places, you may be able to remove the rotten parts and fill them with a soft wood polyester filler. It will help keep your window sill strong for a few more years, but you will ultimately need to replace your window sill.

Is it easy to install your own window sill?

It's not that easy to install your own window sill. That's why we'd always recommend getting a carpenter to replace your window sill for you.

Getting a good finish on a wooden window sill involves cutting it to perfect size and fixing nails and screws in a way that keeps them hidden. You also need to ensure that your window sill is fitted properly to ensure that rainwater doesn't get into your home.

To avoid causing damp problems in your property, we'd suggest getting a carpenter to fit new window sills for you. You can be sure that they're installed correctly this way, and it could even save you money if your DIY project goes wrong and you waste expensive materials.

If you're ready to get new wooden window sills, post your job on HaMuch. We'll put you in touch with local trusted carpenters that are ready to do the work.

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