Window Sill Replacement Cost

Looking into getting a window sill replaced in your home?

This guide covers everything you need to know about replacing window sills. It includes a breakdown of how much different materials cost (PVC, stone, wood, concrete, and MDF window sill prices), typical labour fees, and much more!

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How Much Does a Window Sill Replacement Cost?

The cost of replacing a window sill will vary primarily based on the type of window sill replacement and the size of the installation area.

The cost of having a PVC window sill replaced is generally between £45 and £115, with the cost rising to £120 to £195 for a stone window sill.

Replacing a wood window sill usually costs around £50 to £135, whereas a concrete window sill replacement costs £150 to £255. You'd be looking at paying £40 to £95 to replace a MDF window sill.

Beyond this, the two main factors that impact quotes are ease of access to the window sill and where you're located in the UK.

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Labour Costs and Timescales

The labour cost of a window sill replacement (for any material) is between £30 and £75 for between 1.5 and 3 hours of time. This is based on average labour charges of about £15 to £25 per hour across the UK for this type of job.

(The reason for the £30 figure is that even with 90 minutes of work, you’re likely to be charged for two hours of labour, hence £15 x 2.)

This means that, roughly, around 60% of the cost for a window sill replacement goes towards labour.

Keep in mind: replacing a particularly large window sill or one that is complex to deal with for other reasons (e.g., difficult to reach) may take longer than this.

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What Impacts Window Sill Replacement Costs?

As we’ve discussed, when it comes to replacing a window sill, there are a whole host of factors to take on board. Let’s look at these cost-affecting factors in more detail.

Type of Window Sill Replacement

First and foremost, the cost of replacing a window sill primarily depends on the type you opt for. This would mostly be down to the material used.

The table below shows just the cost of supplies (excluding any labour) and would be what you'd pay if purchasing the replacement window directly from a retailer.

However, in addition to the materials used, the design of the window sill, as well as the quality of the brand/product, could also impact the replacement window sill cost.

Size of Installation Area

Of course, the size of the window sill replacement will also matter. The larger the window sill, the higher the supply price will likely be. In addition, a larger window sill may take a bit longer to install. This could bring up the cost of labour, but in most cases, it won't.

Location in the UK

If you live in the southeast of England, you are probably looking at contractor prices (in general) that are above the national average. On the contrary, those living in the north of England, Scotland and Northern Ireland would probably pay less than in most parts of the UK. All in all, location matters when it comes to what labour prices you can expect.

With all that said, the difference is not likely to be huge, considering that the average labour cost of a window sill replacement is about £50 (assuming a two-hour job). That said, it’s still a cost factor that shouldn’t go overlooked.

Ease of Access

How accessible the window area is could also shape your total bill. The easier a professional can access the work area, the quicker the task will be. Ultimately, a faster job (typically!) translates into lower labour price.

Hidden Problems

Now and then, pulling out an old sill reveals more than you bargained for, like rotten wood, damp patches or blown plaster. If that happens? The fitter may need to repair or replace sections of the frame, treat the rot, or re-plaster the area.

With stone or concrete sills, cracks often need an epoxy repair or full replacement. If the substrate is rotten or blown, allow for extra time and materials (hardener, splices, re-plastering) — this is why a rotten sill can cost more than a straightforward swap.

Custom Sizes & Profiling

Non-standard depths/lengths, bullnose edges, returns into reveals, templating curved bays, or scribing to out-of-true walls add time. Pre-finished or made-to-measure pieces can reduce on-site shaping but may raise supply cost.

What's Involved in a Window Sill Replacement?

Changing a window sill isn’t quite as undemanding as you might think. The old one has to come out very carefully, then the surface underneath needs putting right. Plus, the new sill has to be fitted and sealed in the right way so water can’t get in.

Not sure you have the skills (or the patience)? It’s well worth getting a professional in instead. And it’s a good idea to compare a few quotes before you book someone in.

Before the Job Starts

• Survey and measurements — Check the overall width/depth, check the reveal is square, and jot down any trims, end caps or horns that need matching (internal vs external).
• Condition check — Look for damp, blown plaster, soft timber or loose masonry. Agree any small repairs to the substrate (packing, filler, hardener) before fitting.
• Spec and finish — Choose material (PVC, MDF, wood, stone, concrete), edge profile and overhang. For externals, ensure a fall away from the window and a drip groove.
• Protection and access — Sheet up floors, clear the sill area, and take down blinds or curtains. If paint might contain lead in older homes, plan safe dust control.

During the Job

• Careful strip-out — Score caulk and paint lines, ease off trims, and pry up the old sill without damaging the frame. Remove old fixings and debris.
• Make good — Repair/pack the bearing surface so it’s level and solid. Treat any minor rot; rake out loose mortar on externals.
• Dry-fit and level — Test the new sill for fit, set a slight fall on externals, and check reveals/overhangs are even.
• Fix in place — Bed on suitable adhesive or mortar (material-appropriate), add mechanical fixings where required, and refit or replace end caps/horns.
• Seal and finish — Neatly caulk to frame and walls; for timber, prime cut edges before final paint. For stone/concrete, keep the drip groove clear.
• Extra steps for external sills — Set a slight fall away from the frame, keep the drip groove clear, and weather-proof the finish. Timber/MDF should be primed, undercoated and painted; stone/concrete may need sealing as specified.

After the Job

• Final checks — Confirm level/falls, tight joints and smooth beads; ensure trickle vents aren’t blocked.
• Curing and clean-down — Allow adhesives/caulk/paint to cure before loading the sill with plants or heavy items.
• Handover — You’ll get care notes (e.g., repaint intervals for timber, non-abrasive cleaners for PVC/stone) and confirmation of any small substrate repairs completed.
• Weathering check — Confirm there’s a clear drip groove and a visible fall so rain can’t sit against the frame.

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Building Regulations and Planning Permission for a Window Sill Replacements

For a straight like-for-like sill swap, you probably won’t need planning permission or Building Control. It only gets formal if you alter the window opening, structure, or the property has special status (listed, or in certain conservation areas).

Use this quick checklist to see what applies to your job:

• Swapping an internal sill for the same style: You won’t need planning permission and won’t typically have to inform Building Control either.
• Changing an external sill that matches the old one: Generally okay – you won’t need approvals, so long as the size, slope and drip groove stay the same and the look doesn’t change.
• When Building Control steps in: If you alter the window opening itself, change the height or width, affect escape routes, or carry out major masonry work, then checks may apply.
• When you need planning permission: If your building is listed, this warrants Listed Building Consent, plus, several conservation areas may also ask for approval if the sill’s design or material changes.
• A few practical tips: Never cover trickle vents. Instead, slope external sills so rain can run off, and if the sill is low near a drop, make sure guarding still meets safety rules.

Types of Window Sill Replacement

If you’re not entirely sure what type of window sill you’d like to have installed, this section is for you!

Here, we will look at window sill replacement options such as PVC, stone and wood, discuss their pros & cons and remind you of their average supply prices.

PVC Window Sill Cost

These window sills are a popular choice and come in a wide range of sizes, finishes and colours. This includes PVC window sills that are designed to replicate other more expensive materials like stone.

Among the core advantages of the window sills are their low cost (£15 to £40 on average), moisture- and sunlight resistance, durability and their ability to protect against heat and water.

One concern is that with cheap PVC materials, there is a risk of the presence of formaldehyde, which can be harmful to your health. For that reason and more, it's best not to simply go with the cheapest option you find.

That is unless it also happens to offer the qualities desired, but this is less likely to be the case unless, for instance, the product is on sale. They will also come with a lower load limit than many other stronger choices.

Stone Window Sill Cost

While costly with an estimated supply price of about £90 to £120, natural stone offers a beautiful aesthetic, the most longevity out of any of the choices discussed here, and a wide range of colours/styles to choose from, and they can add value to your property.

In fact, expanding on that last point, natural stone window sills could, for all you know, be the difference between selling a home and not. It might be that an extra benefit is needed to push prospective buyers over the line and to make the offer.

Some issue worth noting with stone window sills is that cracks and scratches can appear over the years. They are also unsuitable for prolonged water exposure. It's also important to ensure paint and acidic liquids do not spill onto a stone windowsill, particularly if it's made of marble.

Wood Window Sill Cost

Timber window sills are fairly commonplace and have been in use for generations. Solid wood window sills are long-lasting, easy to access, and have the potential to add a bit of insulation to your home. Some choose to simply fit wooden window sills as they are, whereas other homeowners prefer to have them painted.

The average cost of wood window sills is £20 to £60. This is the standalone cost as opposed to the total wooden window sill replacement cost.

As for the downsides, like any timber home fittings, wooden window sills are prone to wood rot. To ensure protection against rot and mould, a timber window sill requires maintenance on an ongoing basis.

For a similar option to an ordinary timber window sill replacement but with better protection against dampness and humidity, consider particleboard, which is a type of engineered wood.

MDF window sills are in the same category as particleboard window sills, with MDF standing for medium-density fibreboards. MDF window sills have a supply cost of about £10 to £20 and are, therefore, actually cheaper than regular timber products.

Checklist: Hiring Contractors for a Window Sill Replacement

When hiring a professional to install a window sill, there are some pointers worth considering first. These will help give you the best chances of securing good value for money and finding the best person for the job in your area.

Use this quick checklist before you book a window-sill fitter on MyJobQuote:

• Are they the right trade for your sill? Timber/MDF = carpenter or joiner. Stone/concrete = stonemason. External uPVC sills = window fitter. Check their MyJobQuote profile matches the material you need.
• Have they done near-identical jobs? Ask for recent photos of like-for-like work (internal vs external, bay returns, curved profiles). You’ll find examples and reviews on their MyJobQuote page.
• Is the quote itemised? It should show: labour time, sill type/size, small materials (adhesive, fixings, sealant), finishing (primer/paint/caulk), making-good (plaster patching), and any access kit (tower/scaffold).
• Is waste removal included? Confirm they’ll take away the old sill, packaging and rubble, not just “fit and leave”.
• How will they manage access? Upper floors and tricky externals often need a platform or tower. Get the access cost and set-up time in writing.
• What’s their plan for dust and old paint? In older homes, lead-safe working and tidy dust control matter. If anything looks like asbestos, work should pause and be assessed.
• Do they carry public liability insurance? It’s not a legal must, but it protects you if something goes wrong.
• Finishing and make-good — agree who’s doing priming/painting of timber/MDF, resealing, refitting trims, and any small plaster repairs so there are no surprises.
• Guarantees and aftercare — ask what’s covered if joints open up or the finish fails in the first few weeks.
• Any approvals needed? Like-for-like internal swaps normally need none. Listed buildings and some conservation areas can be stricter for external sills — ask the fitter if they’ll advise.
• Payment terms — avoid large upfront payments for small domestic jobs. Paying after a clean, snag-free handover is standard.
• Compare at least three quotes — posting once on MyJobQuote lets you line up local, reviewed trades and choose on value, not just price.