Loft Conversions

Loft conversion cost calculator

The cost of your loft conversion will depend on a variety of factors. The two key factors are the style of loft conversion you choose, and the size of the your property.

The main kinds of loft conversion are:

Adding a loft room: If you have the space already in the loft, then converting it into a room simply involves adding a staircase, skylights, insulation, and often reinforcing the floor, along with final fitting and decoration.
Dormer loft conversions: The most common style of structural loft conversion, these are an extension to the existing roof. These are suitable for most types of home, including terraced house loft conversions.
Hip to gable conversions: An option for detached and semi-detached homes where the roof has at least three slanting sides, a single hip to gable conversion fills out one of the sides by building a vertical end wall, giving you a larger amount of interior space. A double hip to gable conversion can be done on detached houses, building out on both sides.
Mansard roof conversions: These are the most dramatic style of conversion, involving changing the entire roof structure, adding a flat roof with sloping “walls” at 72 degree angles, and dormer windows added. It adds the most room, but significantly changes the exterior appearance of the property.

Room in loft conversion costs

As the simplest method of converting a loft, this is the cheapest way to proceed, though it is only suitable for some homes. The cost is generally between £15,000 and £50,000, with prices tending to be higher in London and the south east where tradespeople are more in demand.

Dormer loft conversion costs

As dormer conversions are relatively straightforward to add to a home, they are a cheaper type of conversion, with the cost typically coming in at around £31,000 to £78,000 depending on the size of the conversion and other factors, with an average of around £45,000.

Hip to gable loft conversion costs

The added complexity of hip to gable conversions means they are typically more expensive, with a starting price of around £42,000, going up to around £85,000, with an average of around £64,000.

Mansard loft conversion costs

As a mansard conversion involves the most complex and complete overhaul, it is the most expensive option, beginning at £45,000, and going up to around £90,000, with an average cost of £68,000.

Bungalow loft conversion costs

Any of the three main styles of attic conversions can be done to a bungalow if the property is suitable and planning requirements are met, so the costs of a bungalow loft conversion can vary from around £30,000 to £90,000.

Stages of a loft conversion

1) Loft conversion plans costs

It is advisable to get comprehensive plans drawn up for your conversion, either from an architect or an architectural technician. This will lay out exactly what changes will happen and how the finished project will look, taking into account all of the relevant structural changes that need to be made, including all the necessary calculations. A price of around £1,000 plus VAT is fairly typical for this service.

2) Planning permission costs

For the majority of loft conversions, planning permission will not be needed, as the changes will count as permitted developments. However, there will be instances, depending on the scale of the conversion and factors such as if your home is in a conservation area, where planning permitted may have to be applied for - this is currently £172 in England.

3) Get a loft conversion quote

5 )Building regulation costs

Regardless of your planning status, your conversion will have to be inspected by the building regulations department of your local authority to ensure it is being constructed in accordance with the rules, making sure it complies with things like fire safety, access, floor strength and so on. Submitting the plans for inspection and having on-site inspections can cost between around £400 and £800. You may also need a Party Wall Agreement if your work will impact any adjoining properties, for example if you live in a terraced house or a semi-detached home. This requires your neighbours to agree to the work taking place. You are liable for costs such as their surveyor and any damage to their home which may occur as part of the works - it can cost several thousand pounds depending on how complex the agreement is. Another potential cost, though not always needed, is a bat survey if you believe your loft may have bats - this can cost up to £400.

Other loft conversion costs

The ultimate finish of the loft will have a large impact on the cost of the project - for example, if you are simply planning to use the space as a large bedroom, it will cheaper than if you are putting a bathroom in the space, where you will need to purchase the suite, which can cost several thousand pounds. Other factors include things like moving water tanks, if needed, and the number of windows being fitted.

A slate roof will usually cost more to alter than one with concrete roof tiles. Another factor is whether the roof was built with a frame - often found in pre-1960s homes - or with wooden trusses, which are easier to construct but can take less weight. Replacing or reinforcing the trusses can take more work and thus increase the costs.