Lisburn · County Antrim
Bay window subsidence repairs in Lisburn
If your Lisburn bay window has started sticking and a gap has opened at the junction, it is worth finding out whether the bay is still moving. A stable crack needs a straightforward tie-in, whereas an active one may need a new foundation.
Guide price from£530per bay inc VAT
- Postcodes
- BT17, BT27, BT28
- Population
- about 78,000
- Area
- County Antrim
- Pricing region
- Northern Ireland
Why does the ground in County Antrim matter for bay window subsidence repairs?
Lisburn (BT17, BT27, BT28) has around 78,000 residents and sits in County Antrim. If you are just outside Lisburn, we also cover Belfast (7 miles), Newtownabbey (11 miles) and Craigavon (15 miles).
Clay shrinkage is less of a concern in County Antrim, so other causes such as drains, poor footings or older walls are checked first. Historic brine and salt working has caused ground movement in parts of County Antrim in the past. What you mostly find across County Antrim: red-brick terraces in Belfast, Victorian villas, and post-war and newer estates.
Bay window subsidence repairs prices in Lisburn
The ranges below reflect typical Northern Ireland costs for bay window subsidence repairs, including VAT. Scaffold, access and making good can push a job to the top of the range.
| Item | Guide price | Per |
|---|---|---|
| Bay junction crack repair and tie-inest. | £530 – £1,600 | per bay |
| Traditional underpinning of a bay | £2,650 – £6,150 | per bay |
| Mini-piled bay underpinning | £4,400 – £10,600 | per bay |
How we usually approach bay window subsidence repairs
Mini-piled bay underpinning
Small piles are installed to depth around or beneath the bay and linked by a reinforced beam or needles that pick up its weight. It suits deeper soft ground and heavy root activity, and the compact rigs fit into a front garden.
Best for: Deep clay, nearby trees, or poor ground below the bay
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
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.
Agree the repair
The engineer decides between tie-in repairs and underpinning. We confirm a fixed price in writing once the repair is specified, including scaffolding if needed, the bay window, roof flashing and internal making good.
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.
What to look for before calling about bay window subsidence repairs
- Bay roof or lead flashing pulling away from the main wall
- A step or slope in the bay floor towards the window
- Cracks above the bay window head or below the sill
Rules for bay window subsidence repairs in Northern Ireland
In Northern Ireland, the Building Regulations (Northern Ireland) 2012 apply and the council’s building control service approves structural work such as underpinning; minor like-for-like repairs usually need no approval. The Party Wall Act does not apply in Northern Ireland, so work to shared walls depends on deeds and agreement with neighbours.
Questions about bay window subsidence repairs in Lisburn
How much will bay window subsidence repairs cost in Lisburn?
Guide prices for bay window subsidence repairs in Lisburn start from about £530 per bay, including VAT, on Northern Ireland rates. Your fixed written price follows photos or a survey and depends on the extent of the work and access.
Do you cover Lisburn?
Yes, Lisburn is covered, along with postcode districts BT17, BT27, BT28. We also cover nearby Belfast and Newtownabbey.
Is the ground in County Antrim prone to subsidence?
County Antrim is largely basalt over chalk, with soft estuarine 'sleech' along Belfast Lough that is notorious for settlement. Historic salt mining is recorded near Carrickfergus. Only an investigation can say why a particular building has moved.
How long does bay underpinning take?
Traditional underpinning of a bay usually takes about a week on site, and mini-piling a little longer depending on depth. A junction tie-in without underpinning normally takes one to two days. Approvals and any monitoring beforehand add to the overall timeline.
Why do bay windows crack away from the house?
Bays often stand on shallower footings than the main walls, so they react to drying clay, roots and drain leaks that the deeper house foundations escape. Many bays were also never properly tied in, so any movement opens a clean vertical crack at the junction.
Other structural repairs in Lisburn
- Structural crack repairs
- Subsidence insurance claim repairs
- Bowing wall repairs
- Lintel replacement
- Brick arch repairs
Bay window subsidence repairs near Lisburn
Photos of the bay floor, window and junction crack are enough to start; send them about your Lisburn home and we will reply with a view.