The property
A late twentieth-century two-storey semi-detached house in Uxbridge with a single-storey rear conservatory: brick dwarf walls, glazed upper walls and a glazed pitched roof, with its floor about a metre above the garden. Dense shrubs and trees grow right up to it. The area lies in the Colne valley, where published geological mapping shows river terrace gravels and, near watercourses, soft alluvium over clay.
The client's concern
The owner was worried that the conservatory was still moving away from the house. A history of movement, reportedly linked to inadequate foundations, had been disclosed when the house was bought, and a gap of about 60 to 70 mm had been repaired at that time.
What we saw
An open joint of about 8 to 20 mm where the conservatory meets the house, visible inside and out (BRE Digest 251 Category 3 to 4), and wider at the top than at the bottom. The mortar from the earlier repair was cracked and open, the roof glazing had moved by about 10 mm at the junction, and the garden door was sticking. A rainwater downpipe discharged onto the ground right beside the junction.
How we investigated
A Specific Structural Inspection, confined at the owner's request to the conservatory and its junction with the house. We inspected the junction inside and out, the roof and glazing from ground level, and the windows and door, and recorded the drainage and vegetation nearby. The foundations were not exposed and the drains were not tested.
What we found
The tapering gap showed that the conservatory had settled and rotated away from the house. Shallow or inadequate conservatory foundations, as reported, were the most likely underlying cause, possibly made worse by the vegetation alongside and the downpipe discharging at the junction. A single visit could not show whether movement was continuing or was left over from before the earlier repair; that would need monitoring.
What we recommended
Keeping the conservatory would have meant trial pits, drainage testing, an arboricultural assessment, at least 12 months of monitoring and possibly underpinning. The owner preferred to remove it, and we agreed this was a sensible choice.
We set out how to take it down safely from the top down without disturbing the house. Because the floor sits about a metre above the garden, the raised ground was to be kept as a patio with a retaining edge, rather than dug out beside the house foundations, with guarding at the new edge. We also recommended connecting the downpipe to a proper drain, checking the damp-proof course, and inspecting the rear wall of the house once it was uncovered.
Related services
This was a Specific Structural Inspection (SSI). Read more about our structural inspections and subsidence investigations, or see more case studies.
