Service page · Updated 14 May 2026
Instruct SBS for a single combined loft conversion calculation pack: ridge beam, floor strengthening, stair trimmer and dormer steels in one stamped document. Rooflight loft from £800, dormer / hip-to-gable from £1,200, mansard from £1,500.
Fixed fee
From £800
Rooflight loft · One combined pack
Turnaround
7–10 days
Express option for builder/BC pressure
Scope
All-in
Ridge + floor + stair + dormer — one fee
One stamped document covering every structural element of the loft — designed so your builder doesn't need to come back to us mid-job.
Quoted before you instruct. Pricing reflects the engineering work — not floor area.
| Loft type | What's involved | From | Turnaround |
|---|---|---|---|
| Rooflight loft | No dormer. Floor strengthening, light ridge upgrade, stair trimmer | £800 | 7 days |
| Dormer / hip-to-gable | Rear dormer, new gable wall, ridge beam, all steels and floor strengthening | £1,200 | 7–10 days |
| Mansard / complex | Full mansard, multiple dormers, heritage constraints or unusual roof geometry | £1,500 | 10–14 days |
How do I instruct you?
Send architect's plans (or measurements + photos). We quote a fixed fee inside one working day. 50% deposit on instruction, 50% on issue.
Do I need an architect first?
No. Many loft clients instruct us directly on a measured survey to save on architect fees. We can also work alongside your architect if you've already appointed one.
Are revisions included if Building Control queries the design?
Yes — up to two rounds of revisions within six weeks of issue, included. We deal directly with the BC officer.
Do I pay separately for ridge beam, floor and dormer steels?
No. One fee, one combined calculation pack covering every structural element of the loft.
Can you visit site?
Yes, where the existing roof or floor structure is uncertain. Typically inside two working days in Ilford and Thurrock.
Recent projects
Real anonymised projects from the last few months. Specifications shown are indicative — every project gets its own calculation pack.
Twin 203x133x25 UB ridge beams + 178x102x19 UB floor beams; 47x195 C24 floor joists at 400 c/c
Calc pack accepted by Redbridge Building Control; Party Wall Award completed for adjoining owner
Steel ring-beam at eaves, 152x89x16 UB purlins, padstone bearings into party wall pockets ≤ ½ wall thickness
Waltham Forest Building Control approved; structural drawings used for tender pricing
203x133x30 UB ridge, doubled C24 47x220 trimmers around stair opening, 50mm noggings at mid-span
Issued in 8 working days; Havering Building Control approved at first review
Researching dormer options or whether a hip-to-gable is right for your house? Read our Loft Conversion Structural Engineer Guide before instructing.
Next steps
Send through a sketch, plan or photo and we'll come back with a clear written quote — no obligation. Most enquiries are answered the same working day. Phone, WhatsApp and email are in the footer.
Mon to Sat, 8am to 6pm. Most calls answered within 1 hour. Or message us on WhatsApp.
Two offices — Ilford (61 Cranbrook Road, IG1 4PG) and Tilbury (Brunel Close, RM18 8EJ) — covering Ilford, Tilbury, Thurrock, East London and Essex.
