Horsham · West Sussex
Bay window subsidence repairs in Horsham
Many bays in Horsham were butted against the house rather than bonded into it with ties or toothed brickwork. That makes the junction the first place any differential movement shows, even when the bay foundation is reasonably sound.
Guide price from£670per bay inc VAT

- Postcodes
- RH12
- Population
- about 51,000
- Area
- West Sussex
- Pricing region
- South East
Why does the ground in West Sussex matter for bay window subsidence repairs?
Postcode districts RH12 cover Horsham, a West Sussex town of about 51,000 people. Neighbouring towns we cover: Crawley (7 miles), Horley (11 miles) and Haywards Heath (11 miles).
Shrinkable clay is widespread in West Sussex. Ground movement here is more often linked to soils, drains and trees than to mining. Housing stock in West Sussex: Wealden cottages, 1930s semis and bungalows on the coast, and new-town estates in Crawley.
How we usually approach bay window subsidence repairs
Junction crack repair and tie-in
Where movement has stopped, the open joint between bay and house is raked out, stainless ties or helical bars are fixed across it, and the joint is repointed to match. Internal plaster along the crack is cut back and renewed before redecoration.
Best for: Old, stable cracks where the bay is no longer moving
Traditional underpinning of the bay
The bay footing is excavated in short sections and new mass concrete is placed down to firmer ground below the zone affected by roots and seasons. Because a bay is a short length of wall, the work is compact, but it needs building control approval.
Best for: Active bay movement on firm ground at moderate depth
What happens during bay window subsidence repairs, step by step?
Engineer and checks
Where the cause is unclear, an independent chartered structural engineer inspects, sometimes with a trial pit at the bay and a drain survey. We can arrange the engineer. Monitoring may be suggested if the movement could be seasonal.
Carry out the work
Ties are fitted across the junction, or the bay is underpinned in sequence with building control inspecting the dig. The bay window and flashings are checked and eased or resealed where the movement has disturbed them.
Make good inside
Plaster around the bay and along the junction is renewed, the window board is refixed and the room is ready for decoration. Building control paperwork, where it applies, is passed to you for your records.
What to look for before calling about bay window subsidence repairs
- A step or slope in the bay floor towards the window
- A vertical crack where the bay meets the front wall
- Bay window sash or casement sticking or binding
Bay window subsidence repairs prices in Horsham
These are guide prices for Horsham, using South East rates and including VAT. Your written quote follows photos or a survey, and is fixed once the repair is specified.
| Item | Guide price | Per |
|---|---|---|
| Bay junction crack repair and tie-inest. | £670 – £2,000 | per bay |
| Traditional underpinning of a bay | £3,350 – £7,850 | per bay |
| Mini-piled bay underpinning | £5,600 – £13,400 | per bay |
Rules for bay window subsidence repairs in England
In England, underpinning and other work that alters or strengthens a wall or foundation is building work under the Building Regulations (Part A, structure), so building control approves and inspects it. Like-for-like repairs often are not, and we tell you which applies before a price is agreed. Work to a party wall, or excavation close to a neighbour’s foundations, can also need a notice under the Party Wall etc. Act 1996.
Questions about bay window subsidence repairs in Horsham
How much should I budget for bay window subsidence repairs in Horsham?
Guide prices for bay window subsidence repairs in Horsham start from about £670 per bay, including VAT, on South East rates. Your fixed written price follows photos or a survey and depends on the extent of the work and access.
Can you survey a property in Horsham?
We do. Horsham and the surrounding area are covered, including nearby Crawley and Horley. A free initial assessment from your photos is the first step.
Why do houses in West Sussex crack?
North West Sussex around Crawley and Horsham sits on Weald Clay, the South Downs are chalk, and the coastal plain has brickearth and gravels. The Weald Clay is prone to shrink-swell movement near trees. Only an investigation can say why a particular building has moved.
Is a crack between my bay and the house serious?
It is often not serious, especially if it is old, fine and unchanged for years. A crack that is widening, tapering or matched by sticking windows and a sloping bay floor needs looking at. An engineer’s inspection, sometimes with monitoring, will confirm whether the bay is still moving.
Will the bay window need replacing?
Usually not. Most windows can be eased, packed or resealed once the bay is stable. If the frame has twisted badly or the glass has cracked, replacement may be worth considering. Under a claim, upgrades beyond like-for-like are normally priced separately.
Related work in Horsham
- Wall tie replacement
- Resin injection ground stabilisation
- Subsidence insurance claim repairs
- Brick arch repairs
- Boundary and garden wall repairs
Bay window subsidence repairs near Horsham
Send photos of the bay junction inside and out at your Horsham home for a free initial assessment and a guide price.