Loft conversions in Hertfordshire
A new bedroom, office or bathroom in the roof you already have. Free survey at your home in St Albans, Harpenden, Rickmansworth and the villages around them.
Loft bedroom
Study
Bathroom
- Free survey at your home
- Every item priced in writing before work starts
- Drawings first, so you see it before anything changes
- Planning and building regs applications made for you
- St Albans based
Every type of loft conversion
A loft conversion turns the roof space into a proper room with a floor, stairs and windows. Most take 4 to 10 weeks on site, and many need no planning application. Ver Valley Lofts & Extensions covers St Albans, Harpenden, Rickmansworth and the villages around them, starting with a free survey at your home.
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Dormer
A box built out from the rear slope, giving full head height across the new room. A popular choice, L-shaped too.
Get a dormer quote -
Hip-to-gable
The sloping side of a hipped roof built up into a straight gable wall. Can be paired with a rear dormer.
Get a hip-to-gable quote -
Velux and rooflight
The roof keeps its shape, so the loft needs about 2.2 m of height under the ridge already.
Get a Velux quote -
Mansard
The rear slope rebuilt almost upright, for the most space of any loft.
Get a mansard quote
Thinking of extending instead? Rear, side return, wrap-around, double-storey and garage conversions
Which loft conversion suits your roof?
Dashed line: your roof today. Solid line: after the conversion.
Dormer
A box built out of the rear slope, so the loft gets more head height and floor space.
- Typical UK cost
- £30,000 to £60,000
- Time on site
- 6 to 8 weeks
- Planning
- Permitted development within the size limits. No dormer on a front slope facing a road
Hip-to-gable
The sloping side of a hipped roof is built up into a straight gable wall, which opens up the loft.
- Typical UK cost
- £40,000 to £65,000
- Time on site
- 6 to 8 weeks
- Planning
- Permitted development within the size limits
Velux and rooflight
The roof keeps its shape. Windows go into the slope and the loft gets a proper floor and stairs.
- Typical UK cost
- £15,000 to £35,000
- Time on site
- 4 to 8 weeks
- Planning
- Not normally needed, as the roof space is not extended
Mansard
The rear slope is rebuilt nearly upright, with a flatter roof on top.
- Typical UK cost
- £55,000 to £80,000
- Time on site
- 8 to 10 weeks
- Planning
- Permitted development only within the size limits. Check with the council
Size limits: 40 m³ of extra roof space on a terrace, 50 m³ on other houses, no higher than the roof. Conservation areas need planning permission. We check your address first.
Mansard loft conversions
A mansard rebuilds the rear slope almost upright, with a flatter roof on top, so the new floor gets close to full-height walls.
It gives the most space of any loft type, and costs the most. It changes the shape of the roof, so we check with the council before relying on permitted development. In a conservation area it needs planning permission.
- Typical UK cost
- £55,000 to £80,000
- Time on site
- 8 to 10 weeks
- Planning
- Permitted development only within the size limits. Check with the council
Do you need planning permission for a loft conversion?
Often not. Most lofts can go ahead as permitted development if they stay within these limits.
- No more than 40 m³ of extra roof space on a terraced house, 50 m³ on a semi or detached house.
- Nothing higher than the highest part of the existing roof.
- No dormer on a front roof slope that faces a road.
- Side windows obscure-glazed, and fixed shut unless the opening part is more than 1.7 m above the floor.
- Dormers set back 20 cm from the eaves, except where a hip-to-gable or L-shaped dormer joins the main roof.
- Materials similar in appearance to the rest of the house.
- No balcony.
In a conservation area, roof extensions need planning permission. A Lawful Development Certificate from the council confirms in writing that your loft is permitted development, which is the kind of evidence a buyer will want to see when you sell.
What do St Albans and Three Rivers councils say about lofts?
Each council has its own rules on top of the national ones. We check your address against them before the survey.
St Albans City and District
87% approvedof 980 homeowner planning decisions, July 2025 to June 2026
In a conservation area, the council can support a dormer that is sized to suit the house, avoids a terracing effect and fits the local roofscape. Flat-roofed dormers are supported only where they are characteristic of the local area.
Article 4 directions take away roof and extension rights in four areas only: Verulam and Fishpool Street, Sopwell Lane and Albert Street, Cunningham Avenue, and Childwickbury, which reaches into Harpenden at Beesonend.
Three Rivers
91% approvedof 617 homeowner planning decisions, July 2025 to June 2026
None of the council’s Article 4 directions takes away loft or extension rights. A dormer should sit lower than the main roof: below the ridge, in from either end and back from the wall below. Hip-to-gable on a semi-detached house is discouraged, because it can unbalance the pair.
In Croxley Green, the advice is against raising the ridge, and against hip-to-gable other than a half hip, though the council decides each case on its merits.
How long does a loft conversion take, and what does it cost?
Published UK ranges for 2026, not our quote. London and the South East run roughly 15 to 35% higher.
| Type | Typical cost | Typical time |
|---|---|---|
| Velux or rooflight | £15,000 to £35,000 | 4 to 8 weeks |
| Rear dormer | £30,000 to £60,000 | 6 to 8 weeks |
| Hip‑to‑gable | £40,000 to £65,000 | 6 to 8 weeks |
| Mansard | £55,000 to £80,000 | 8 to 10 weeks |
Drawings, approvals and party wall notices come before work starts. Drawings, engineer, party wall surveyor and building control fees usually cost extra. Full cost guide
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Building regulations and party walls
Every loft conversion needs building regulations approval, because it turns roof space into a room.
Building control checks the structure, so the new floor is strong enough and the house stays stable. It also checks fire safety and a safe way out, the stairs, insulation, ventilation and sound between floors. The application is made for you, and you get a completion certificate at the end, which you may need when you sell.
If the work cuts into, or sits on, a wall you share with a neighbour, the Party Wall Act means giving them written notice between two months and a year before work starts.
Loft conversion questions
Do I need planning permission for a loft conversion?
Often not. Under the government’s permitted development rules, a loft can go ahead without an application if it adds no more than 40 cubic metres on a terraced house or 50 on other houses, stays below the existing ridge and has no dormer on a front slope facing a road. Conservation areas need planning permission.
How long does a loft conversion take?
On site, a Velux loft usually takes 4 to 8 weeks, a dormer or hip-to-gable 6 to 8 weeks and a mansard 8 to 10 weeks, according to MyJobQuote’s 2026 guides. Drawings, any planning application and building regulations approval come first, so allow extra time before work starts.
Which loft conversion gives the most space?
A mansard gives the most, because the rear slope is rebuilt almost upright, and a dormer comes next. A Velux loft adds no volume, so it needs height already: Homebuilding & Renovating’s guide gives a rule of thumb of 2.2 metres from the top of the floor joists to the underside of the ridge.
Can I convert my loft in a conservation area?
Yes, but the government’s permitted development rules do not cover roof extensions there, so you need planning permission. St Albans council’s 2026 Local Plan says dormers in conservation areas may be supported if they are appropriately sized, avoid a terracing effect and suit the local roofscape. In Moor Park, an Article 4 direction also covers front and side rooflights.
What does Three Rivers council look for in a dormer?
Three Rivers council’s Development Management Policies (2013) ask for dormers that are subordinate to the main roof, set below the ridge, in from either end and back from the wall below. The same guidance discourages hip-to-gable on semi-detached houses, because it can unbalance the pair. None of the council’s Article 4 directions removes loft rights.
Does a loft conversion add value?
It can. Nationwide found in October 2025 that adding a large double bedroom and a bathroom to a three-bedroom, one-bathroom house, by loft conversion or extension, can add as much as 24% to its value. How much yours gains depends on the house, the street and the finish.
Can we stay at home during a loft conversion?
Usually, yes. Loft specialists answering on MyJobQuote say the work is mostly done from the scaffolding, and the only time they need to come into the house is when the new stairs go in. If the loft is too low to build the new floor over the ceiling below, that ceiling has to come out.
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