Your questions, answered

Subsidence occurs when the soil supporting a building's foundations shifts or sinks downward. Bay windows are particularly at risk because they often sit on shallower footings than the main structure and project beyond the front wall. When the soil beneath shifts or shrinks, the bay can pull away from the main wall, frames go out of square, and diagonal cracks appear at window corners. Left unchecked, the gap between the bay and the main wall widens and structural distortion tends to worsen.

Diagonal cracks running from the corners of the window frame, gaps opening where the bay meets the main wall, and a window that sticks or no longer closes squarely are worth taking seriously. Cracks that are noticeably wider at one end, or that have appeared quickly and grown over a few weeks, suggest active movement rather than minor settlement. Cracking in the mortar beds of the brickwork stepping in a staircase pattern is also a recognised indicator.

A specialist will attend the property, examine the bay window structure and its junction with the main building, assess crack patterns and widths, check the surrounding ground and drainage, and identify what is likely causing the movement. Based on those findings, the specialist advises whether immediate repair is needed, or whether crack monitoring over a period of time is the more appropriate first step. The specialist sets out the available options in writing after the assessment.

A structural subsidence specialist attends the property in person. They record crack patterns, measure widths, examine the bay window structure and the ground conditions around it, and check drainage. The report sets out the cause of the movement, the condition of the foundations, and the repair options. All assessment, ground investigation and repair work is carried out by that specialist firm. You can get a free quote for the repair work once the visit has taken place.

Cost depends on the cause of the movement, the repair method selected, how far the bay has shifted from the main wall, the depth required to reach stable ground, and site access. Resin injection to stabilise soil beneath a shallow footing costs less than underpinning a longer run of foundation. No single figure applies across all properties. A specialist visits the property and provides a written quote based on what they find. That quote is free.

Yes. If a survey report or homebuyer's report has flagged cracking, previous movement or shallow foundations on a bay window, a specialist can attend the property ahead of exchange. When describing your situation, include the property address, your expected exchange date, and any findings already noted in the survey. The specialist can then set out what investigation is needed and provide a written quote for any work.

A general builder can fill visible cracks, but if the ground beneath the bay continues to move, those cracks reopen and the gap at the wall junction widens again. A subsidence specialist identifies the cause of the ground movement first, then selects a repair method suited to the soil type and foundation depth. They can also produce documentation that satisfies a home insurer or mortgage lender, which a cosmetic repair will not achieve.

How quickly a specialist can visit depends on the firm's current workload and the property's location. Repair timescales vary with the method chosen: fitting a root barrier or injecting resin beneath a shallow footing takes less time than underpinning a longer section of wall. The specialist firm will set out a realistic programme for the work once the cause has been confirmed and a method agreed.