Finchley Two-Storey Bay: Structural Rebuild, North London
A two-storey front bay in Finchley that had been carrying the floor above on window frames alone: taken down to ground floor cill level and rebuilt with load-bearing bay posts, a welded steel ring beam, reinforced blockwork tied into the house, and the original corbelled brickwork. Completed in December 2025.
Project Overview
The house is divided into flats, and its two-storey front bay had a problem common in London: when the windows were replaced in the past, they were fitted without proper load-bearing bay posts, so the frames had been carrying the structure above. The bricks at the sides of the bay were damaged, two bricks under the cill were cracked, and props were already holding up the first floor of the bay.
A chartered building surveyor (MRICS) designed the repair, wrote the tender and acted as contract administrator, inspecting the work on site. The job ran under the FMB Plain English minor works contract, with the tenants given notice before the start.
Holding the House Up
Before anything came out, the bays were sealed off from the flats with timber and OSB hoardings and the floors protected. Ten props went in across the two floors, five more with Strongboys held the wall above, and two supported the porch canopy, which the bay partly carries.
The fascias, windows and sub-cill came out, followed by the first floor brickwork and studwork and the bay ceiling and coving, with precautions for the lime plaster. The 24 sealed window units were removed and stored for refitting, and the 53 corbelled bricks, which are almost impossible to replace, were salvaged.
A Structure That Carries Itself
At cill level the stone sub-cills were lifted and rebedded level, the cracked bricks replaced with class B engineering bricks, and two steel bearing plates bedded on resin. New bay posts with head and base plates and load-transfer studs went in to the manufacturer's bay pole manual, with the studs rechecked the next morning.
A 200x150 steel ring beam, mitred and fully butt welded, was fabricated to a site survey and lifted in on 12 November, with 150mm bearings into the main wall and a damp-proof course over it. The first floor was rebuilt in 215mm lightweight aircrete blockwork with galvanised bed-joint mesh, four 2 metre stainless spiral ties and stainless starter profiles into the main wall, and joist hangers built in. The blockwork was set back so that the new render would let the corbels project exactly as before.
Getting the Blockwork Right
The steel beam was designed for lightweight blockwork, so the block choice mattered. We set out the options for the surveyor in writing and agreed 215mm 7N lightweight blocks with bed-joint mesh and stainless ties, keeping the job on programme.
How the Job Ran
- Preparation: tender, site meeting, quotation and contract, with the tenants given notice.
- Temporary works: hoardings, props and demolition down to cill level.
- Structure: bay posts fitted and the steel ring beam lifted in.
- Rebuild: blockwork, corbels rebedded, windows refitted, props struck.
- Finishes and handover: render, fascia and interior finishes, then the completion inspection with the surveyor.
Scope of Works
Temporary works
- Hoardings sealing the bays from the flats, floor protection
- Ten props across two floors, five props with Strongboys, two under the porch canopy
Structure
- Bay demolished to ground floor cill level
- Sub-cills rebedded, cracked bricks replaced, steel bearing plates on resin
- Load-bearing bay posts with load-transfer studs
- Welded 200x150 steel ring beam with 150mm bearings
- 215mm 7N lightweight blockwork with bed-joint mesh and stainless ties
- Original corbelled brickwork rebedded over the beam
Finishes
- 24 sealed window units refitted on the new posts
- Stainless steel mesh render carrier, two-coat render and pebble-dash to match
- New moulded fascia
- Insulated plasterboard and skim inside, new bay ceiling and matched coving
Certificates and Handover
The surveyor carried out the completion inspection on 11 December 2025 and has since recommended Alstruct for another job.
The Result
A front bay that now carries itself on proper posts and a steel beam, with the original corbels, render and fascia put back so that from the street it looks exactly as it did.
Read our guide: Bay Window Structural Problems: Signs, Causes and Repair.
If you are planning similar work in Finchley or nearby, see our Finchley page or browse our other projects.
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