How to get a loft conversion

14 April 2022 – 7 Minute Read

Loft conversions are one of the most common home renovation projects in Britain. Given the rising cost of housing in the UK they can be one of the most straightforward ways of upgrading to an extra room in your home.

A converted loft can add a lot of value to your property too. In fact, Nationwide Building Society recently noted that investing in a loft conversion can raise the value the average UK home by as much as 20%.

But, if done incorrectly they can sometimes be problematic. In fact, 36% of builders and tradesmen surveyed by a Direct Line Home Insurance have experienced issues when carrying out loft conversions in the UK, including issues with building regulations, loft space and ventilation.

We spoke to Aldershot-based conversion specialists Marble Construction Ltd to answer ten of the most common questions and issues that may arise with your loft conversion. Make sure you avoid those issues and find out everything you need to know about planning your loft conversion project correctly with Yell Home & Garden’s loft conversion project guide.

1. What does a loft conversion involve?

Dormer window in construction. Image via Marble Construction

There are three main types of loft conversion. These are:

Room-in-roof conversion The most straightforward process, a room-in-roof conversion, also called a ‘Velux conversion’, keeps the existing roof shape but adds in skylight-style Velux windows for light and ventilation. The existing shape and angle of your roof will dictate the size of the final room.

Dormer conversion A loft conversion with the addition of open, square Dormer windows, projecting out from the slope of the roof. The are usually at the rear of the property. This option is quite common and good for those that may need a little more height or space, or have awkward shaped roofs.

Hip-to-gable conversion This is the more complicated of the three forms of loft conversion. A ‘hip-to-gable’ involves replacing the existing roof hip (that’s the slope of your roof that falls to the side of your house) with a flat gable end. This takes the the angle of the roof pitch from 45 degrees up to around 90 degrees.

Bruce Rathod, sales director at Marble Construction advises: “As long as your property isn’t a listed building, or in a conservation area, it’s possible to undertake a double hip-to-gable extension without planning permission.” The project must also conform to certain size limits. ( See ‘Will I need planning permission?’, below. )

2. Is my loft suitable for a conversion?

Almost every roof can be converted as long as you comply with building regulations. The main area to consider when looking at converting your loft is the height of your roof. Marble’s Bruce Rathod advises: “To meet government building regulations, the minimum height for a converted loft space is 2.1 metres, measured from the top of the ceiling joist to the floor. An optimum standing height for the room is usually 2.3-2.4 metres.”

However, there are possibilities if your ceiling doesn’t meet this minimum height: “For shorter room heights, adding Dormer windows above the opening to the stairway can provide the height needed,” suggests Bruce.

Loft conversion in construction. Image via Marble Construction

3. Will I need planning permission for a loft conversion?

For most loft conversion projects, planning permission is not normally required. However, there are certain limits and conditions to roof structure and positioning. If your project is likely to exceed these limits, then you will be required to submit a planning application. These include:

  • If your house is on designated (conservation, listed) land, a loft conversion is not permitted.
  • Your additional roof space must not exceed 40 cubic metres for terraced houses and 50 cubic metres for detached and semi-detached houses. This includes any previous extensions or roof changes made to the property, even from before when you bought the house.
  • Extensions at the front of the house (facing a highway) must not reach beyond the plane of the existing roof slope. This includes dormer windows.
  • Your extension does not go higher than the highest part of the roof.
  • Materials should be similar to your existing house style.
  • Balconies or verandas are not permitted.
  • If it’s possible protected species, such as bats, are using your roof space, a survey or licence may be required.

4. What about building regulations?

Marble Construction recommend to their clients that, even though planning permission applications aren’t needed, the homeowner apply for a Certificate of Lawfulness to their local council. This will confirm all building regulations will be met by your project. As well as head height ( see Question 2, above ), the main of these is fire regulations .

According to fire regulations, the staircase from your loft space must not pass through any other room. You will need to install fire doors and a corridor which leads to the main route out of the building in case of a fire. The staircase must also have handrails fitted.

Remember that if your project doesn’t meet standard building regulations, you may not be able to classify the extra room as a bedroom or living space when selling your property, which may reduce the value of the project.

5. Will my loft conversion get too hot?

Firstly remember that, as hot air rises, your loft space will always be the warmest room in the house. But, it’s also important to make sure that your building firm doesn’t try to cut costs with a cheaper form of insulating material. “Make sure your contractor is using building regulation-approved 175mm thick rigid insulation in all the walls to make sure the room is properly insulated,” recommends Bruce. This will keep heat in during the winter months but allow for good ventilation throughout the space in the summer.

Complete loft conversion. Image via Marble Construction

6. We have a tank in our loft, can I just build around it?

Heating systems with header tanks in the loft space aren’t suitable if considering a room conversion, so Bruce recommends you move this from the attic: “You should convert your heating system to a combination boiler or system with pressurised cylinder before undertaking a loft conversion project.”

Usually, a good loft conversion team will have a specialist plumber in their team, who will be able to help you with this, but if not, it is worth investing in a plumber beforehand to make the change before you call in the builders. Find a plumber to help you on .

“If you really can’t change your heating system, then it is possible to keep the tank where it is,” says Bruce, “but it’s important to bear in mind that this will take up space and be noisy, warm and annoying for the new residents of the converted room.”

7. My house has a shared party wall. Will a loft conversion cause structural damage?

While there is no requirement to submit planning permission for a loft conversion, Marble Construction recommends that it is often worth submitting a party wall notice to your neighbour. This will alert them to the work being undertaken, and give them the chance to raise any structural concerns.

“The structural supports for a party wall should never go in further than 100mm,” recommends Bruce, “at this length it will never bear load onto your neighbour’s property and is unlikely to cause structural damage.”

If you have an old property, or are worried about building support, also make sure you have the space surveyed by a chartered surveyor to check there are no structural issues.

Internal finished loft conversion with en suite bathroom. Image via Marble Construction

8. How long will a loft conversion take to complete?

The average loft project, with a dormer will take around six weeks to complete. For more complicated properties and fitted furnishings etc, this can take a little longer.

9. How much will a loft conversion cost?

Loft conversions cost from £20,000 up to £50,000 depending on type of project, size of the house and materials needed. Your region of the UK will also affect the cost.

We spoke to Marble Construction, who work largely in the Hampshire and Berkshire areas, who advise that prices for their projects start from around £35,000 for a double bedroom Velux conversion. This can rise up to £40-50,000 for a double bedroom conversion with an en suite and rear dormer window.

Bruce Rathod from Marble advises that generally the cost of a loft conversion is in the same region as the cost of stamp duty when purchasing a new house – one reason why many homeowners chose to undertake a renovation instead of putting their home on the market.

10. How much value will it add to my home?

In terms of added value, figures from a survey by Nationwide Building Society reveal homeowners who add a loft conversion with a double bedroom and a bathroom can add more than 20% on a three-bedroom house, that’s around an extra £42,000 based on average UK house prices.