A hip-to-gable loft conversion with rear dormer on a 1930s semi-detached in Solihull — the original hipped roofline squared off into a vertical gable wall to gain full standing headroom across the loft, supported by a new steel ridge beam. Delivered as a master bedroom with built-in wardrobes, a generous en-suite, and a third Velux to the front for natural light. Nine-week site programme, fixed price, building control sign-off and party wall award both filed before site start.
A family of four on a quiet residential road in Solihull. Two parents in their late thirties, both working from home three days a week, and two daughters — aged seven and four — sharing a bedroom that was no longer big enough to handle the eldest's homework setup and the youngest's bedtime stories at the same time. The house was a substantial three-bedroom 1930s semi-detached with the original hipped roofline still in place. Loft was being used for storage. The neighbour, a couple of years earlier, had converted theirs — same hip-to-gable, same rear dormer — which made the planning conversation simpler and the visual outcome consistent across the pair of semis.
The brief was structurally straightforward and personally significant: gain a fourth bedroom upstairs to become the new master, free up the existing master to give one of the children their own room, and add an en-suite so the family bathroom didn't have to handle four people getting ready at once. We were one of three contractors quoting. We won the work because our quote was the only one to bundle the planning application, the Party Wall Agreement with the attached neighbour, and the Building Control sign-off into a single fixed-price preconstruction phase, with a guaranteed site start date contingent only on consents being granted in normal time.
Pre-construction took eleven weeks (planning approval at week eight, party wall award at week ten, building control plans approved at week eleven). On-site programme ran nine weeks. Roof watertight by the Friday of week four, the hard hold-point we set against weather risk. Building control completion certificate issued on the Tuesday following handover. The eldest daughter slept in her own room for the first time on the Sunday of week ten. The four-year-old asked for the same a week later, which the family is still working out.
The brief was developed over two design meetings. Priorities, in their stated order:
A 9-week hip-to-gable conversion is a structurally significant build with multiple regulatory dependencies before site start and several hard-to-recover-from constraints once on site. Six interrelated challenges had to be locked down from the first quote meeting.
The semi-detached property shares a wall with the neighbour. Hip-to-gable work requires a formal Party Wall Notice under the Party Wall etc. Act 1996, with eight weeks for the neighbour to consent or appoint a surveyor. We served the notice in week 1 of pre-construction, the neighbour appointed an agreed party wall surveyor at week 4, and the Award was signed at week 10. Site start at week 12 was contingent on the Award being in place. No surprises, no delays.
Removing the hipped end of the roof requires a new horizontal steel ridge beam to take the loads previously carried by the hip rafters down through the new gable wall. Structural calculations were prepared by our engineer at design stage: 203 × 102 UB section, 2.4m span, supported on the new gable wall and a padstone over the existing party wall. Beam delivered to site in two weeks, craned into position over a single morning during the open-roof phase.
Building Regulations Part B requires a protected escape route from a third-storey loft conversion to the ground floor. The whole of the existing stairwell from loft to ground had to be upgraded to 30-minute fire-resistant construction: existing internal doors replaced with FD30 fire doors, intumescent strips and smoke seals, ceiling and stairwell wall finishes upgraded where required, and mains-wired interlinked smoke alarms installed on every floor. Fire risk assessor reviewed at first fix, snagged at second fix, signed off at handover.
New stairs to a loft conversion must comply with Part K: minimum 600mm clear width, maximum 42-degree pitch, minimum 1.9m headroom (1.8m allowed at one side of a stairwell). On a 1930s semi-detached the available run is tight. Stair designed at planning stage to land over the existing first-floor landing rather than into the third bedroom — preserving full bedroom footprint — with a quarter-turn winder set against the gable wall to manage the rise within the available run. Headroom 1.92m at the worst point, signed off by Building Control.
Open-roof phase carries the highest weather risk on the project. We costed in a full weatherproof scaffold tent as a fallback at quote stage, and committed to a hard hold-point of "roof watertight by Friday of week 4" against the weather forecast. In practice the weather held and the tent was not deployed; the new ridge beam, gable wall, dormer framing and felt-and-batten weatherproofing were complete by Thursday of week 4 and final slate covering by Friday. No water ingress at any point.
The family stayed in the property throughout. Sealed plastic dust separation at the existing first-floor ceiling hatch and at the new stairwell head, all heavy structural and noisy work scheduled within an 8.00am to 5.00pm window with no Saturdays except one (the steel ridge beam install, where the crane permit window required a Saturday morning). Daily 4.30pm tidy and dust-down. School runs and bedtimes uninterrupted across the nine-week programme.
Loft conversions succeed or fail on the parts that happen before the scaffold goes up. Pre-construction is roughly half the project; the bricks-and-timber side is the visible half. Our approach was structured around four disciplines, two pre-construction and two on-site.
Pre-construction owned end-to-end, costed into the fixed price. Two competing tenders treated the planning application, the Party Wall Agreement and the Building Control plans submission as the homeowners' problem, or as items to be invoiced separately. We led all three: planning drawings prepared and submitted by us, Party Wall Notice drafted and served by us, surveyor appointment coordinated, Award filed before site start, building control plans submitted and approved before strip-out. Single fixed price covering pre-construction and site, single point of accountability.
Structural design before quote, not after deposit. Steel ridge beam section, gable wall structural specification, new floor joist sizing, stair design and stair landing position were all worked out at quote stage. The clients saw the structural calculations before they signed the contract. No "we'll work that out when we see what's up there" — everything modelled and signed off before the first slate came off the roof.
Roof watertight as a calendar commitment. Open-roof phase is the project's biggest weather risk. We committed to a calendar week (week 4) for "roof watertight" and costed in a weatherproof scaffold tent as a fallback if the forecast turned. In practice the weather held; the tent was on order and would have been on site within 24 hours if the seven-day forecast had shown more than light rain at any point during the open-roof phase.
Building Control sign-off treated as a workstream. Five Building Control inspections through the project: foundation/structural (week 2), pre-plaster (week 5), drainage (week 6), pre-completion (week 8), and final completion (week 9). Each inspection booked and confirmed in advance, every comment closed out within 48 hours, completion certificate issued on the Tuesday following handover. No outstanding items.
Forty-five working days on site, preceded by eleven weeks of pre-construction (planning, party wall, building control plans). The 9-week site programme sequenced against a Friday-of-week-4 watertight hold-point and a Friday-of-week-9 handover.
Planning drawings and design and access statement prepared and submitted. Party Wall Notice served on the attached neighbour. Surveyor appointment coordinated. Structural calculations prepared for the steel ridge beam, gable wall and new floor joists. Building Control plans submitted. Planning approval granted week 8. Party Wall Award filed week 10. Building Control plans approved week 11. Site start the following Monday.
Full perimeter scaffolding erected with edge protection. Existing roof tiles and battens stripped from the hipped end. Hip rafters carefully demolished, original ceiling joists protected to maintain the existing first-floor ceiling integrity. Sealed plastic dust barrier installed at the first-floor ceiling hatch. Foundation Building Control inspection booked for week 2.
New gable wall built up from existing eaves to ridge level: brick outer skin matching existing brick on the front and rear elevations, blockwork inner leaf, cavity insulation. Padstone bedded over the party wall to receive the steel ridge beam. Saturday morning: 203 × 102 UB steel ridge beam craned into position, bolted to padstone and gable wall. Building Control structural inspection signed off Tuesday afternoon.
New floor joists installed at 400mm centres, hangered into the existing wall plates and bolted to the new gable wall. Rear dormer framing erected: timber stud walls, flat roof structure, cheeks. New roof slope rafters fitted between ridge beam and existing wall plate at the front. Felt and batten weatherproofing applied to all roof surfaces by Friday afternoon, providing first-stage weather protection.
Slate covering laid across new roof areas matching existing roof finish. Lead flashing dressed at all junctions: ridge, valleys, dormer cheeks and abutments. Three Velux roof windows installed (two existing positions plus the new front-facing third). Dormer cheek and front cladding completed and weather-sealed. Friday afternoon: full roof structure watertight, photographed and signed off as the project's hard hold-point. Internal works can now proceed weather-independent.
Electrical first fix throughout the loft and the upgraded escape route: bedroom and en-suite circuits, mains-wired interlinked smoke alarms on every floor of the house. Plumbing first fix to en-suite: hot/cold supplies, soil routing through new floor void with 1:40 fall to existing stack. Wet UFH manifold positioned, pipework laid in en-suite. Warm-roof PIR insulation installed between rafters with a 50mm air gap above; full vapour barrier sealed at every penetration. Pre-plaster Building Control inspection signed off Friday.
Plasterboard fitted to all walls and ceilings, including 12.5mm fire-rated board to the protected escape stairwell. Two coats of plaster, finishing skim. UFH-compatible self-levelling screed poured in the en-suite. New staircase fabricated off-site delivered Tuesday and installed Wednesday-Thursday: quarter-turn winder against the gable wall, balustrades temporary at this stage. Drainage Building Control inspection booked and signed off Friday.
En-suite tanking applied across wet zone walls and floor, 24-hour static flood test passed and signed off mid-week. Large-format porcelain tile installed across en-suite walls and floor. Decoration started in the new bedroom: two coats of mist coat plus first topcoat. FD30 fire-rated doors installed along the protected escape route at all stair-adjacent rooms, intumescent strips and smoke seals fitted. Decoration completed Friday in bedroom, primer in en-suite.
En-suite sanitaryware installed: walk-in shower (frameless 10mm tempered glass screen, brass fittings), twin vanity with under-mount basins, wall-hung WC with concealed cistern, heated towel rail. Built-in wardrobes installed along the gable wall: full-height carcasses, sliding-door fronts, internal hanging and drawer fittings. Second-fix electrics throughout the loft and along the escape route: light fittings, sockets, smoke alarms commissioned and tested. Pre-completion Building Control inspection booked for end of week.
Final decoration in the en-suite. Carpets fitted in bedroom and stairwell. Stair balustrade installed and finished. Snagging walkthrough Tuesday; eight items identified, six cleared by Wednesday afternoon. Final Building Control completion inspection Thursday morning, certificate issued Friday by post (received Tuesday following). Handover Friday at 4pm. Eldest daughter's first night in her own room (the converted old master) the following Sunday.
The technical detail behind a structurally significant loft conversion delivered to building regulations and to programme.
203 × 102 UB steel ridge beam, 2.4m span, calculated to BS EN 1993. Bolted to padstone bedded over the existing party wall and to a structural connection on the new gable wall. Beam encased in 30-minute fire-resistant boarding to comply with Part B.
New gable wall: brick outer skin matching existing on front and rear elevations, 100mm blockwork inner leaf, 100mm cavity with full-fill mineral wool insulation. Built up from existing eaves to new ridge level. Wall ties at 450mm vertical centres. Cavity tray over the steel beam padstone.
Flat-roof rear dormer, 4.2m wide, 2.4m projection. Timber stud frame with 100mm PIR insulation in the cavity. Cheeks clad in lead-effect GRP. Flat roof finish: warm-roof construction with 150mm PIR over the structural deck, single-ply membrane covering with kerb-side detailing.
Warm-roof construction. 150mm PIR between rafters with a 50mm air gap above and an additional 25mm PIR underdraw. Calculated U-value 0.15 W/m²K, beating the 0.18 W/m²K Part L target by a clear margin. Full vapour control layer sealed at every penetration. Loft hatch insulated and draught-sealed.
Protected escape route from loft to ground floor: 30-minute fire-resistant construction along the stairwell. FD30 fire doors with intumescent strips and smoke seals to all stair-adjacent rooms. Mains-wired interlinked smoke alarms on every floor. Fire-rated boarding to the steel ridge beam encasement.
New softwood-and-MDF staircase fabricated off-site to fit the available run. Quarter-turn winder against the gable wall. Pitch 41 degrees, clear width 800mm, headroom 1.92m at the worst point (Part K minimum 1.8m at side, 1.9m central). Hardwood handrail at 900mm. Toughened glass balustrade panels.
Three Velux roof windows: two existing front-facing positions retained and replaced with new units, plus a third new opening on the front matching the new gable proportions. All units are GGL Centre-Pivot UFC, double-glazed, U-value 1.0 W/m²K, with white-painted timber frames internally.
Walk-in shower with frameless 10mm tempered glass screen, brass-finish thermostatic valve and overhead rainfall plus hand-held shower. Twin vanity with marble-effect porcelain worktop and under-mount basins. Wall-hung WC with concealed cistern. Wet UFH below large-format porcelain tile. Schluter Kerdi tanking with 24-hour flood test passed.
A 3-bed semi-detached converted into a 4-bed semi with en-suite, delivered against a 9-week site programme on a fixed-price contract preceded by 11 weeks of pre-construction. The original hipped roofline is now a vertical gable wall matching the neighbour's earlier conversion. A 203 × 102 UB steel ridge beam sits 4.2m above the new floor, supporting a roof finished to a U-value of 0.15 W/m²K — well above the Part L target. The new master bedroom occupies the back of the loft with built-in wardrobes the full length of the new gable wall; the en-suite occupies the rear dormer with walk-in shower, twin vanity and wall-hung WC. Three Velux roof windows light the room from the front.
The family reorganisation was the brief's real outcome and the room layout did its job. Parents moved into the new loft master, freeing the existing first-floor master to become the eldest daughter's bedroom. The four-year-old kept her own (smaller) room. The home office stayed where it was. A 3-bed semi became a 4-bed semi with an en-suite for around £49,000, delivering an estimated £55,000 to £75,000 of property value uplift in the local Solihull market — the financial case being a useful side-effect of the brief's primary purpose, which was that the eldest daughter wanted her own room and now had it.
We had three contractors quote. The other two both wanted us to handle the planning application, the Party Wall Agreement and the Building Control submission ourselves — or to invoice those separately as additional fees. Building Group bundled all three into the fixed price and committed to a calendar week for the roof being watertight. Both turned out to be exactly the things that mattered. Pre-construction took eleven weeks, every step communicated to us by email with copies of every document, and we genuinely had nothing to do except read the updates. Site phase was nine weeks, the family stayed in the house throughout, and the roof was watertight on the Friday they said it would be. The eldest had her first night in her own room ten days after handover. We hadn't realised how much it was going to change the household until it happened. The four-year-old wants her own room now too, which she'll get when she's a bit older.
If you're thinking about a hip-to-gable, a rear dormer, an L-shaped dormer or a mansard, we'll come out for a free design consultation, walk the property with you, and put a fixed-price design-and-build proposal — including the planning application, party wall agreement and building control submission, all costed in — on your kitchen table within ten working days.
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