Window Sill Replacement Cost: A Pricing Guide

Quick Cost Overview

• The average window sill replacement cost in the UK is £150 to £350 per window, including materials and labour.
• Interior uPVC sills are the most affordable option, with materials typically costing £30 to £60.
• Exterior concrete sill replacement is one of the more labour-intensive jobs, usually costing more.

In this cost guide, we will cover:

1. Average Window Sill Replacement Costs
2. Interior Window Sill Replacement Costs
3. Exterior Window Sill Replacement Costs
4. What Affects the Cost of Window Sill Replacement?
5. Signs Your Window Sill Needs Replacing
6. Choosing the Right Window Fitter
7. Find Window Fitters Near You on MyBuilder
8. FAQ: Common Questions About Window Sill Replacement Costs

Average Window Sill Replacement Costs

Window sill replacement is a relatively straightforward job, most are completed in one to three hours per window. The material you choose, and access can push costs in either direction.

The table below gives a useful starting point for budgeting, covering both materials and labour for a standard replacement.

Window Sill Type	Average Cost (Supply and Fit)
Interior uPVC	£90-£160
Interior wood	£130-£220
Interior stone	£160-£300
Exterior uPVC	£100-£180
Exterior concrete	£150-£280
Exterior stone	£180-£350

Labour alone for a straightforward replacement typically runs £60 to £150 per sill, with tradespeople charging around £25 to £50 per hour.

If removal of the old sill reveals damage to the surrounding frame or masonry, additional repair costs of £20 to £80 may apply. For a broader window project, see our window fitting cost guide for context on how sill costs compare to full window replacement.

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Interior Window Sill Replacement Costs

Interior window sills are primarily an aesthetic feature. They frame the window from inside, provide a ledge for plants or ornaments, and contribute to the finished look of the room.

The most popular materials for interior sills are wood, uPVC, and stone, each with different cost and maintenance implications.

uPVC

The most affordable interior option. uPVC is lightweight, moisture-resistant, and easy to wipe clean, making it particularly practical for kitchens and bathrooms. It is available in white and a range of wood-effect finishes. Material costs typically run £30 to £60, with supply and fit sitting at £90 to £160.

Wood

A classic choice that suits period properties and traditional interiors. Wood can be painted or stained to match the room and has a warmth that uPVC cannot replicate. The downside is that it requires periodic repainting or sealing to prevent moisture damage and warping. Material costs run £50 to £80, with supply and fit at £130 to £220.

Stone

Stone sills - marble, granite, or engineered stone - are the premium interior option, offering a durable and high-end finish. They are resistant to scratches, stains, and moisture, and rarely need maintenance beyond wiping clean.

Material costs run £80 to £120, with supply and fit at £160 to £300 depending on the stone type and the complexity of the cut.

Exterior Window Sill Replacement Costs

Exterior window sills have a structural function as well as an aesthetic one. They help to channel rainwater away from the wall beneath the window and protect the surrounding masonry.

Deteriorating exterior sills can allow water ingress, so timely replacement is worth prioritising. The main materials used externally are uPVC, concrete, and stone.

uPVC

The lowest-cost exterior option and a practical choice for most residential properties. uPVC does not rot, chip, or fade, and requires virtually no maintenance. It is lightweight and straightforward to fit, which keeps labour costs lower. Material costs run £40 to £60, with supply and fit at £100 to £180.

Concrete

The traditional choice for exterior sills on post-war and modern brick properties. Pre-cast concrete sills are ordered to length and are durable under UK weather conditions, but they are heavy and require more careful handling and pointing work during installation. Material costs run £70 to £100, with supply and fit at £150 to £280.

On period properties where the original concrete sill has cracked, repair using epoxy mortar is sometimes possible at lower cost before committing to full replacement.

Stone

Stone exterior sills - typically limestone, sandstone, or reconstituted stone - are most commonly found on Victorian, Edwardian, and older period properties. They provide excellent weather resistance and are often required on listed buildings or in conservation areas to match the existing character of the building.

Material costs run £100 to £150, with supply and fit at £180 to £350. Specialist sourcing of matching stone for period properties can push costs higher.

What Affects the Cost of Window Sill Replacement?

Several variables influence the final price beyond the choice of material. Understanding these upfront helps you compare quotes accurately.

Window size

Larger windows need wider sills, which means more material and slightly more labour for cutting and fitting. Bay windows and wider casements cost more than standard windows.

Floor level and access

Ground-floor windows are straightforward to access. First-floor and above may require scaffolding, access towers, or ladders, adding £50 to £200 depending on the setup required.

Existing damage

Removing an old sill sometimes reveals rot in the window frame, damaged masonry, or failed sealant that needs addressing before the new sill can be fitted. Additional repair costs typically run £20 to £80 but can be higher for significant structural issues.

Material weight and complexity

Heavier materials like concrete and stone require more careful handling and may need additional support or pointing work, adding to labour time.

Location

Labour rates in London and the South East are typically 15 to 25% higher than the national average.

Signs Your Window Sill Needs Replacing

Not all window sill problems require full replacement! Some can be repaired at lower cost. Here is how to tell whether your window sill needs repairing or replacing.

• Signs that repair may be sufficient: Small cracks, minor flaking paint, or localised surface damage on exterior concrete or stone sills can often be addressed with epoxy filler or re-pointing, costing £50 to £150 rather than full replacement.

• Signs that replacement is needed: Soft or spongy wood indicating rot that has penetrated the sill and crumbling or deeply cracked concrete that has allowed water behind the wall.

• When to act quickly: Water ingress around a window sill can cause damage to the surrounding wall and frame that escalates costs considerably if left unaddressed. If you notice damp patches on the interior wall beneath a window, a failed sill seal or cracked exterior sill is a common cause worth investigating promptly. Our new window cost guide is useful if the assessment reveals wider window issues that need addressing at the same time.

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Choosing the Right Window Fitter

Window sill replacement is within the capability of a competent handyman for interior timber or uPVC work, but exterior concrete or stone sills - particularly on period properties - are better handled by an experienced window fitter or specialist stonemason. Here is what to check before hiring.

• Experience with your material. Not every window fitter regularly works with stone or concrete. Ask whether they have replaced the same type of sill before, particularly if you have a period property where matching is important.

• Insurance. Your fitter should carry public liability insurance. For any work at height, check this is in place before work begins.

• Written quote. A proper quote should specify the sill material, whether waste disposal is included, and what happens if additional repairs are found once the old sill is removed. Verbal agreements leave too much ambiguity.

• Check reviews. On MyBuilder, you can read reviews from previous customers and browse photos of past work before making contact. Our aluminium window cost guide also has useful notes on what to look for when assessing window fitter credentials more broadly.

Find Window Fitters Near You on MyBuilder

Window sill replacement is a job where getting the right person matters - a poorly fitted sill, particularly on the exterior, can allow water ingress that leads to much more expensive problems down the line.

On MyBuilder, you can post your job for free and receive interest from local window fitters who can assess the work, confirm the right material, and provide a clear written quote.

Browse their profiles, check customer reviews, and compare quotes before committing to anyone.

All tradespeople on MyBuilder undergo checks at registration - such as ID documents, company details, certifications for regulated jobs and skill assessments - allowing you to hire with confidence.

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FAQ: Common Questions About Window Sill Replacement Costs

What Is the Average Cost to Replace a Window Sill?

The average cost to replace a window sill in the UK is £150 to £350 per window, covering both materials and labour. Interior uPVC sills sit at the lower end of this range, while exterior stone sills on period properties can push toward or beyond the upper end. You can browse photos of completed window sill replacement jobs on MyBuilder to get a sense of what local fitters charge in your area.

How Much Does It Cost to Replace an Exterior Concrete Window Sill?

Replacing an exterior concrete window sill typically costs £150 to £280 supply and fit for a standard residential window. Concrete sills are heavy and require careful pointing work during installation, which is why labour costs are slightly higher than for uPVC. Pre-cast concrete sills are usually ordered to the specific length of the window.

How Much Does It Cost to Replace a Rotten Window Sill?

Replacing a rotten timber window sill typically costs £130 to £220 for a standard interior replacement, but if the rot has spread to the surrounding frame or wall, additional repair costs of £20 to £80 or more may apply.

It is worth having the frame assessed at the same time as the sill -- catching frame damage early prevents costs escalating further.

Can I Replace a Window Sill Myself?

For interior timber or uPVC sills on ground-floor windows, DIY replacement is possible if you are comfortable with basic carpentry and sealant work. Exterior replacements - particularly concrete or stone at height - are better left to a professional, as incorrect fitting or pointing can allow water ingress. Any work involving stone on a listed building or conservation area property should always be handled by an experienced specialist.

How Long Does Window Sill Replacement Take?

A standard window sill replacement takes one to three hours per window for a competent fitter. Exterior concrete or stone sills that require pointing and rendering take longer - typically two to four hours. If additional frame repairs are needed, allow extra time.