Hip to Gable Loft Conversion Solihull: Costs, Planning Rules, Timeline and What Can Go Wrong
Most families in Solihull semis hit the same problem. The loft has potential, but the sloping hip roof cuts the usable floor area in half. You end up with a cramped bedroom and wasted triangular voids at each gable end.
A Hip to Gable loft conversion replaces the sloping hip with a vertical gable wall, giving you full-height headroom right to the party wall and often an extra 30% to 40% of floor space. The result is a proper double bedroom with an ensuite, or two single bedrooms where you previously had awkward eaves storage.
But Hip to Gable conversions in Solihull come with planning rules, Party Wall obligations, and structural constraints that catch families out. This guide explains the process, realistic costs, timelines, and the mistakes that delay projects or trigger refusals.
What is a Hip to Gable loft conversion
A hip roof slopes down on all four sides of the house. A Hip to Gable conversion builds up the sloping end wall to create a vertical gable, flush with the party wall on a semi-detached house or set back slightly on a detached property. This vertical wall replaces the triangular hip section and gives you usable floor space where you previously had dead eaves.
Hip to Gable is often combined with a rear dormer to maximise headroom and floor area across the entire loft. The gable gives you width, the dormer gives you depth.
Permitted development rules in Solihull
Hip to Gable conversions can fall under permitted development Class B, but the rules are strict and the constraints often surprise homeowners.
Houses only: Permitted development rights for roof enlargements don't apply to flats or maisonettes. This route is for houses only.
Volume allowance: You can add up to 40 cubic metres of resulting roof space on a terraced house or 50 cubic metres on a detached or semi-detached house. This is cumulative and includes the Hip to Gable section, any dormer, and any previous roof additions. If an earlier owner added a dormer or roof extension that used part of the allowance, your remaining volume shrinks. Go over this cumulative volume, and you need a Householder planning application.
Height limits: The new roof's highest point must not exceed the existing roof's highest point. You cannot extend forward of the roof slope that faces the highway.
Materials: The gable wall and any dormer must use materials that are similar in appearance to the existing house. On most Solihull semis, that means facing brick for the gable, not render or weatherboarding.
Eaves set-back for dormers: Dormers must be set back 0.2m from the original eaves, measured along the roof slope. Don't use the gutter as your datum. The Hip to Gable section itself is not a dormer and is not caught by this set-back rule.
Side windows: Any side-facing windows must be obscure-glazed with opening parts 1.7m above floor level to protect neighbour privacy.
Party wall alignment: On semi-detached houses, the gable typically builds flush to the party wall. You must serve Party Wall notices on your neighbour before you start, even if the work stays within permitted development for planning purposes.
Conservation areas and Article 4 directions: If you're inside a conservation area or Article 4 zone, permitted development won't apply. Check Solihull's conservation area list and Article 4 web map before you bank on PD. If you're in Knowle, Olton, or Hampton-in-Arden conservation areas, you'll need a Householder application and should expect stricter design control on materials, fenestration, and roof form.
Eligibility quick check
Houses only (PD rights don't apply to flats or maisonettes)
Semi-detached or detached house (terraced houses have tighter 40m³ volume limits)
Hip to Gable plus any dormer plus any previous roof additions within 40m³ (terrace) or 50m³ (semi/detached) of resulting roof space
New roof height does not exceed existing ridge
No extension forward of the highway-facing roof slope
Materials similar in appearance to the existing house
Dormers set back 0.2m from original eaves, measured along the roof slope (Hip to Gable section exempt)
Side windows obscure-glazed with opening parts 1.7m above floor
Not in a conservation area or subject to Article 4 (check Solihull's conservation area list and Article 4 map)
No past planning conditions removing PD rights
Policy explainer: Permitted Development for roof enlargements
Why it exists: Speeds up modest roof changes that meet national Class B limits without full planning scrutiny.
What it means: If you stay within Class B rules, you avoid a householder planning application, but the limits are tight and cumulative. Previous roof additions count against your allowance. Houses only, flats excluded.
Workarounds: If you breach PD limits, live in a conservation area or Article 4 zone, submit a Householder application instead with a design case for your proposal.
Do you still need paperwork?
Yes. Apply for a Lawful Development Certificate (Proposed) so your permitted development rights are formally confirmed. This protects resale value and satisfies mortgage lenders who want written proof.
Fee: LDC for proposed works is half the Householder planning fee. From 1 April 2025, that's £264, plus the Planning Portal service charge £70.83 plus VAT if you apply online. Total around £349 including VAT.
Timeline: Solihull aims to decide LDCs in 8 weeks from validation.
Policy explainer: Lawful Development Certificate
Why it exists: Provides a legal decision that your proposal is lawful under permitted development.
What it means: You avoid planning judgement on design quality, but must prove you meet every PD rule precisely, including cumulative volume.
Workarounds: If refused, revise to meet PD limits or switch to a Householder planning application with a design case.
Building Regulations, you must hit
A loft is a new habitable space, so Building Regulations apply regardless of the planning route. Two requirements catch most Solihull projects:
Stairs and headroom: You need a fixed stair, not a ladder. Aim for 2.0m headroom. Accepted loft relaxation: 1.9m over the centreline and 1.8m at the handrail side under a slope. Non-compliant stairs stall Building Control sign-off.
Fire safety and structure: You'll need a protected escape route (fire doors to all habitable rooms), often requiring fire doors at the top of the stairs and mains-wired smoke alarms on every floor. Structure requires steel beams, correctly sized joists and trimmers, and often new floor joists to handle bedroom loads.
Policy explainer: Building Regulations for lofts
Why it exists: To make the new floor safe to use and safe to escape in a fire.
What it means: Expect structural steel, compliant stairs with proven headroom, thermal upgrades, and fire protection measures.
Workarounds: If headroom is tight, a dormer positioned over the stairs or a minor ceiling drop often solves it. We model this in section drawings before you commit.
Common mistakes that cause problems
Ignoring previous roof additions
The 50m³ volume allowance is cumulative and includes any previous roof extensions or dormers. If an earlier owner added a dormer that used 20m³, you only have 30m³ remaining. We check the planning history and calculate the cumulative volume before you start.
Assuming the Hip to Gable gives you automatic space
Volume calculations are precise. A large rear dormer combined with a Hip to Gable often pushes you over 50m³. If you exceed the limit, you need a Householder application. We model this in 3D so there are no surprises.
Ignoring Party Wall timing
You must serve Party Wall notices before you start, even if your design is permitted development for planning purposes. Assume your neighbour will appoint a surveyor and budget 6 to 8 weeks for a Party Wall award. Starting work without an award risks an injunction.
Underestimating structural work
Hip to Gable conversions remove the original hip rafter that helped brace the roof. You'll need steel beams to support the new gable wall, often new ridge beams to span the extended roof, and additional floor joists to handle bedroom loads. Loft floor joists in 1930s semis are often 100mm x 50mm at 400mm centres, not strong enough for bedroom loads. Get a structural engineer involved early, not after the builder has priced the job.
Missing stair headroom requirements
Non-compliant stairs are the single biggest cause of Building Control delays. Aim for 2.0m headroom, with accepted loft relaxation to 1.9m over the centreline and 1.8m at the handrail side under a slope. We prove headroom with section drawings before you apply for Building Regulations.
Missing fire safety requirements
Building Regulations require a protected escape route from the new loft bedroom. That usually means a fire door at the top of the stairs, mains-wired smoke alarms on every floor, and sometimes upgraded fire resistance on the stair enclosure. Budget for these from the start.
Forgetting drain surveys and trial openings
Structural surprises and drainage conflicts cause the worst cost overruns. Trial openings to check joist sizes and drain surveys to map sewer routes reduce late changes that stall the build.
Missing conservation area or Article 4 checks
If you're in a conservation area or Article 4 zone, permitted development won't apply. Plan for a Householder application and expect stricter design control. Check Solihull's conservation area list and the Article 4 web map before assuming PD applies.
Timeline that actually holds
Week 0 to 1: Measured survey and feasibility check. Confirm existing roof structure and PD volume available, including any previous roof additions.
Week 2 to 3: Scheme drawings, cumulative PD volume calculation, staircase section with headroom proven, outline structural design.
Week 4: Submit Lawful Development Certificate application.
Week 4 to 12: LDC determination, typically 8 weeks from validation. Prepare Building Regulations package in parallel so you don't lose time.
Week 12 to 14: Appoint builder, serve Party Wall notices where relevant. Neighbour has 14 days to respond. If they appoint a surveyor, awards often add 6 to 8 weeks.
Week 14 to 26: Build, typically 6 to 10 weeks on site for a straight Hip to Gable with rear dormer, stairs, and ensuite.
Total programme from feasibility to completion: 14 to 26 weeks, depending on Party Wall process and structural complexity.
Policy explainer: Party Wall
Why it exists: Prevents and resolves boundary disputes when you build on or near a shared wall or dig near a neighbour's foundations.
What it means: Most Hip to Gable lofts need Party Wall notices for cutting into the party wall or new bearings for steel beams.
Workarounds: Serve the correct Party Wall notice early. Budget time and cost for a Party Wall award if your neighbour appoints a surveyor. Don't start work without an agreed award, or you risk an injunction.
Local example: Shirley, Solihull
A 1930s semi in Shirley wanted a master bedroom with an ensuite in the roof, using Hip to Gable plus a modest rear dormer.
We checked the planning history for previous roof additions (none found). We confirmed the cumulative PD volume at 48 m³, within the 50 m³ limit for a semi-detached house. We applied for a Lawful Development Certificate. Decision in 7 weeks.
We modelled the staircase in section to prove 1.9m headroom over the centreline and 1.8m at the handrail side. Materials specified: facing brick to match the existing house, roof tiles to match the main roof, dormer setback 0.2m from the original eaves measured along the roof slope.
The structural engineer specified steel beams to support the new gable, new 225mm floor joists to handle bedroom loads, and additional roof ties to brace the extended ridge. Building Control approved the design.
Party Wall notices served. The neighbour appointed a surveyor. Award agreed in 6 weeks. Build completed in 10 weeks, including snagging.
Why it worked: Cumulative volume kept under the 50m³ cap, dormer setback from eaves as required and measured correctly, materials matched the existing house, stair headroom proven with section drawings, and Party Wall process started early, so it didn't delay the build.
Costs to build in 2025
Guide prices for Hip to Gable loft conversions in the West Midlands range from £60,000 to £80,000 for a typical Hip to Gable with a rear dormer, bedroom, and ensuite. These are shell-plus-first-fix costs, including stairs, structure, insulation, plasterboard, electrics, and basic plumbing.
Worked example: typical Solihull 1930s semi
Hip to Gable plus full-width rear dormer, 28 to 32m² floor area:
Build cost: £60,000 to £80,000 plus VAT
Structural engineer: £1,200 to £2,000
Building Control: £600 typical
Party Wall surveyor (if neighbour appoints): £1,500 to £3,000
Architect or designer fees: £2,200 to £4,500
LDC application: £264 plus £70.83 plus VAT Planning Portal charge (total around £349)
Contingency (10% to 15%): £6,000 to £12,000
Total budget: £72,000 to £100,000, including contingency and professional fees.
What drives the range: Structural complexity, bathroom specification, stair design, access constraints, and roof pitch. If your loft has a central chimney stack that needs removing or diverting, add £3,000 to £5,000. If you're replacing the entire roof structure rather than extending it, costs move to the top end.
High-spec bathrooms, Velux roof windows with electric blinds, bespoke joinery, and oak staircases push costs higher. Budget an extra £8,000 to £15,000 for premium finishes.
Programme: 6 to 8 weeks is a common on-site window for standard scopes. Allow up to 10 to 12 weeks with heavy structural work or services moves.
Your options, costs, and risks
Option A: Hip to Gable with rear dormer (PD if within cumulative volume)
Best for maximising headroom and usable floor area.
Pros: Maximum headroom and floor space across the entire loft. Often stays within permitted development if designed precisely and no previous roof additions exist.
Cons: Highest roof spend due to structural complexity. Cumulative volume cap can restrict layouts if you have previous roof additions.
Cost: £60,000 to £80,000 typical for a bedroom plus ensuite. Budget £72,000 to £100,000, including all fees and contingency.
Suits: 1930s semi-detached in Shirley, Olton, and Solihull needing a proper double bedroom with an ensuite.
Option B: Keep the hip, add large rear dormer (PD if within rules)
Best for modest budgets or where the existing hip is shallow.
Pros: Slightly lower cost than Hip to Gable. Simpler structure, less steel required.
Cons: Less width at the stair landing. Headroom can be marginal at the eaves.
Cost: £50,000 to £70,000 typical for a bedroom plus ensuite. Budget £60,000 to £85,000, including all fees and contingency.
Suits: Lofts where the hip is shallow or the cumulative volume cap is tight due to previous additions.
Option C: Rooflights only (PD)
Best for high existing roof pitches and tight budgets.
Pros: Lowest cost and fastest build. Simple structure, no Party Wall notices required.
Cons: Limited floor area and headroom at the edges. Often no space for an ensuite.
Cost: £27,000 to £40,000 depending on specification and finishes. Budget £35,000 to £50,000, including all fees and contingency.
Suits: High existing roof pitches in Knowle or Dorridge, storage conversion, or home office use where a full bedroom spec isn't needed.
Risks and how we design around them
Conservation areas or Article 4: Class B PD roof enlargements are excluded on designated land. Check Solihull's conservation area list and Article 4 web map before you start. If you're in Knowle, Olton, or Hampton-in-Arden, expect a Householder application (fee £528 from 1 April 2025) with stricter design control.
Cumulative volume breach: Prior dormers or large gables from previous owners can push you over 40m³ or 50m³. We check planning history, calculate cumulative volume early, and model alternatives if you're close to the limit.
Stair headroom: Non-compliant stairs stall Building Control sign-off. We fix this with a small dormer positioned over the stair, smarter stair position, or local ceiling adjustments. Section drawings prove compliance before you commit.
Drain or structure surprises: Trial openings to check joist sizes and drain surveys to map sewer routes reduce late changes that blow budgets and delay completion.
Admin creep: LDC is usually 8 weeks. We run Building Regulations drawings in parallel so the site start doesn't drift while you wait for approvals.
Party Wall delays: If your neighbour appoints a surveyor, budget 6 to 8 weeks for a Party Wall award. We serve notices early and coordinate surveyor appointments so this doesn't stall the build programme.
FAQs
Do I need planning permission for a Hip to Gable loft conversion in Solihull?
Often no if you meet Class B permitted development limits, including cumulative volume from previous roof additions. Houses only, flats and maisonettes don't have PD rights. We recommend a Lawful Development Certificate as written proof to protect resale value. LDC fee: £264 from 1 April 2025, plus Planning Portal service charge.
Does the 0.2m eaves set-back apply to the Hip to Gable part?
No. The 0.2m set-back rule, measured along the roof slope, applies to dormers only. The Hip to Gable section is not a dormer and is exempt from this set-back requirement.
What if my house is in a conservation area like Knowle or Olton?
Class B permitted development doesn't apply on designated land. Check Solihull's conservation area list and Article 4 map. You'll need a Householder planning application (fee £528 from 1 April 2025) with closer scrutiny on materials and design.
How long does it take on site?
A straight Hip to Gable with rear dormer is commonly 6 to 8 weeks. Allow 10 to 12 weeks if the structure is complex or you're moving services.
What stair rules should I know?
Aim for 2.0m headroom as standard. Accepted loft relaxation: 1.9m over the centreline and 1.8m at the handrail side under a slope. We prove this with section drawings before you apply for Building Regulations.
Do I need Party Wall notices for a Hip to Gable conversion?
Yes. The gable builds flush to the party wall on semi-detached houses, and you'll be cutting into the party wall or adding new bearings for steel beams, which triggers the Party Wall Act 1996. Serve notices at least two months before you plan to start.
Does a Hip to Gable conversion add value?
Hip to Gable conversions can improve resale appeal and marketability. Valuation varies by location, finish quality, and local market conditions. The conversion solves the space problem while you live there and creates a proper bedroom where you previously wasted loft space.
See your options clearly before you commit
We check the cumulative permitted development volume on your street, including any previous roof additions, model the stair and headroom in section to prove compliance, verify the conservation area and Article 4 status, and confirm the correct route for your Hip to Gable loft conversion in Solihull. We handle the LDC, Building Regulations, structural engineer coordination, and Party Wall process so the build runs to plan.
Most families in Solihull underestimate cumulative volume limits, discover stair headroom problems after the builder has priced the job, or miss Party Wall timing and face injunctions. We flag those risks upfront, design around the constraints, and keep the programme on track.
Projects across Solihull, Shirley, Knowle, Olton, Dorridge, and Warwickshire welcome. Book a short call to discuss your project.
Author: Mark McTernan
McTernan Design, Solihull
Tel: 07955 572811 | mark@mcternandesign.co.uk | YouTube channel
