Select Page


A great way to expand a home without having to expand its footprint and the ideal option for those looking to get the most space out of their existing homes, whether it’s for an expanding family, a new hobby, or the need for a dedicated home office space. Everything from costs and planning approval to the best design concepts for your project is covered in our guide to converting a loft.

A great article was written by the Federation of Master Builders. You can read the whole article here Below is our interpretation of that article.

Loft conversions are especially useful in areas where obtaining construction permits for an expansion is complex and hard, or where there simply isn’t enough outside space. It’s also worth noting that, according to Nationwide, adding an extra bedroom and bathroom to a standard three-bedroom, one-bathroom house will increase the value by about 20%.

Is it possible to transform my loft?

Certain lofts are better suited to conversion than others. Obviously there is a cost and it can be expensive and time-consuming, so make sure the end result is a useful space and/or adds the value you hoped for. The following factors will decide whether or not your loft can be converted:

Head height that is available

The height of the head should be determined from the top of the loft floor joists to the underside of the ridge beam. While the building code allows for a head height of 2.2m, after a new floor covering has been installed and the ceiling finish has been applied, a much more comfortable height is 2.4m.

The angle of the roof

The smoother your loft conversion would be, the steeper your roof pitch is, with most angles above 30 degrees working best. The more head height is open, the steeper the roof pitch (see above).

Roof construction type

A cut roof or a trussed roof is the two most common roof structures. With the majority of houses constructed before the 1960s having cut roofs, a quick peek in your loft will show which you have. Those constructed after the late 1960s typically have trussed roofs. Rafters, joists, and purlins are used in a cut roof, which leaves the rest of the triangular space below open. W-shaped trusses (or supports) provide braced support and pass through the cross section of the loft, essentially covering some of the gap you’ll need to build usable space. Both are adaptable, but they will necessitate different methods.

Working with a structural engineer and a trained contractor, make sure the opposing roof slopes in a trussed roof are completely supported and bound together at the base (usually with new floor joists) as well as close to the apex with new collars. Steel beams are also installed between load bearing walls to support the new floor joists and the rafter portion, as well as a steel beam at the ridge. Before any of the old trusses are cut, this new structure must be placed in place.

You might also discover that the rafters need to be strengthened, which can be done by doubling them up and attaching new ones alongside, or by using sheets of directed strand board as a wind brace.

In the roof, you’ll find water tanks and chimney stacks.

If your water tank is in the loft, you’ll have to move it. Alternatively, you could get rid of the tank completely and replace it with a mains-fed hybrid boiler or a pressurised unvented hot water cylinder. This can be placed in every room of the building (such as in an airing cupboard).

If your loft has a chimney stack, you may want to remove it to create more room. In this situation, it is important that you consult a structural engineer and hire a competent contractor. Although this is a task that will certainly increase costs and timeframes, it will not preclude you from transforming your loft. Check how this will affect your neighbour’s structure and complete any party wall specifications.

Headroom available for the stairwell

Even if your loft has the requisite amount of headspace, you can run into problems if there isn’t enough room for a staircase to lead up to it. Building codes provide a minimum of 1.9 meters of headroom in the middle of the flight and 1.8 meters at the edges (where there will be sloping roofs). You’ll also need to make space for the stairwell on the lower level.

Types Of Loft Conversions You Can Have

In the United Kingdom, there are five major styles of loft conversions. The type you want should be determined by your current roof structure and shape, the amount of money you want to spend, and, in some cases, planning constraints. Your builder, house designer, or specialist will be able to provide you with additional information.

Loft conversion with a dormer

Many people prefer a flat roof dormer loft conversion because it is one of the simplest and most cost-effective forms of conversion available.

Instead of roof lights, a dormer loft conversion projects vertically from the sloping portion of the roof and uses regular windows. They may be as large as the entire roof or as small as a few smaller dormer windows spaced at regular intervals. The box-like shape creates an easy-to-use space with flat ceilings and walls, making it a perfect way to add headroom.

Although they are not always as attractive as other forms of conversions, they can be considered permitted production.

A gabled dormer, with a pitched roof rather than a flat roof, is more visually appealing but may be more costly and restrict internal headroom.

Loft conversion with a mansard roof

A mansard conversion is similar to adding an additional storey to a home and is suitable for heritage homes and terraced house loft conversions. Keep in mind that the party wall between houses will almost always need to be increased, which will necessitate appropriate agreements.

A mansard loft conversion includes modifying a sloped roof’s roof structure to create an almost vertical wall – typically 72 degrees. The roof remains flat, and the current roof construction includes windows. The majority of mansard conversions are done from gable wall to gable wall.

The most popular location for mansard loft conversions is the back of a building, but they can also be added to the side or front. Double mansard roofs, which are attached to both the front and back of the building, are also an option.

This style of conversion is typically more costly than other forms of conversions, takes longer, and requires planning permission in the majority of cases.

Roof Light

These are almost often the most cost-effective way to transform a loft. The existing room is preserved, with the addition of roof windows maybe Vellux. The floor will need to be strengthened, and stairs will need to be installed. For the room to be habitable, it will also require electrical, plumbing, and insulation.

Roof lights are a simple and cost-effective way to bring in natural light and ventilation while causing minimal damage to your existing living room.

Until flashings are installed and the tiling around the new window is finished, the roof lights’ frame will be fitted into a new opening in the roof.

This is a decent choice for small loft conversions or basic loft bedrooms, but keep in mind that you’ll need at least 2.25m of head height in the room’s centre to properly build up the floor. Due to the lack of headroom, the new loft stairs will need to be placed in the centre of the space.

In the vast majority of instances, a roof light loft conversion does not necessitate planning permission (although it may if the roof lights will be at the front of the house).

Loft conversion from hip to gable

This is an option for those searching for ideas for bungalows or semi-detached houses. A hip to gable loft conversion, in layman’s words, straightens the slanted (hipped) end of a roof to create a vertical wall (the gable end).

The old roof is removed, and the end wall is raised to create a new gable with a traditional pitched roof. Internally, this provides a decent amount of space and plenty of headroom. Because of the new vertical wall, regular window openings for natural light can now be added.


Ready-made conversions, which are frequently constructed with a steel frame, are built off-site and craned into place after the house’s roof has been removed. Many modular loft companies will assist you with obtaining planning permission approval.

This tends to be simpler and needs little on-site labour; you can even choose packages that include doors, windows, electrical, and bathroom installations. A Building Regulations certificate and a Part P Electrical certificate are included with certain modular lofts. To ensure a good fit and a smooth installation, precise measurements and preparation will be needed.

Adding A Bathroom

If you want a new bedroom, you should think about adding an unsuited or bathroom to your as well, as access to the toilet downstairs may be more tricky.

You will almost certainly need the services of an experienced contractor and plumber to complete the job to the appropriate building regulation standards. If you’re considering adding a bathroom, let your builder know as soon as possible. The following are the key problems with bathroom loft conversions:

  • Getting water up to the loft at a good pressure
  • Taking waste water out of the loft and down
  • The floor is being reinforced to support the weight of the sanitary ware
  • Ensure that the bathroom floor is designed to withstand flooding, damp weather, and leaks by consulting the contractor and structural engineer. On the walls, marine grade plywood will be needed, as well as a waterproof tile backing board.

Selecting A Builder

Make sure you hire a contractor who can help you with any aspect of your project. Based on your relationship with the contractor, their experience with the type of project you’re working on, and the feedback from previous clients, make your decision. Check for valid insurance to the minimum amount of coverage.

Use our Find a Builder app to find a builder for your loft conversion or complete form here for 3 quotes.. Members of the FMB are specialists in their fields, having been carefully vetted and independently reviewed prior to entering to ensure that they meet the high quality requirements.

Until deciding on a contractor, get at least three quotes and keep in mind that the cheapest option isn’t necessarily the strongest. For advice on making the best decision for your project, consult our guide.

Will It Be Subject To Permits?

If you live in a historic structure, you’ll need Listed Building Permit, and if you live in a conservation area, an Area of Outstanding Natural Beauty, or a National Park, you’ll almost certainly need to apply for planning permission.

In England, a loft conversion does not normally require planning permission if the following conditions are met:

  • For terraced houses, the new roofing adds no more than 40m3 of space, and for detached and semi-detached houses, no more than 50m3. Keep in mind that any previous roof extensions would be counted against this allowance.
  • The extra room does not extend beyond the current roof slope that faces the road
  • No extension is higher than the current roof’s highest point
  • There are no balconies or elevated floors
  • The new roofing materials are either an exact match for the original or very similar
  • Obscured glazing and a 1.7-metre-high opening characterize the side-facing windows
  • Unless it’s impractical, dormers and other additions (except hip-to-gables) are set back at least 200mm from the original eaves.
  • The exterior face of the house’s original wall is not overhung by any extensions.

You would need to apply for building permits through the local council if all of the above rules are not followed. Your contractor, architect, or specialist should be able to tell you whether you need planning permission and even assist you in obtaining it.

Wales and Scotland: There are common planning conditions in both Wales and Scotland, which can be found in full on the planning section of the Welsh Government and Services website or at, respectively.

Northern Ireland: Anyone converting a loft can visit the nidirect Government Services website in Northern Ireland.

What Building Regulations Are Required?

There is one principle to remember when it comes to building regulations: loft conversions always need building regulations approval, regardless of whether or not planning permission is necessary. Your contractor, architect, or specialist can assist with the preparation of building regulations plans, structural requirements, and estimates, as well as ensuring that the project complies with legal obligations so that you can receive approval.

What are the rules and regulations?

  • New windows must be large enough to escape through in the event of a fire, which means that egress window openings would be needed for all habitable rooms on the first floor (not bathrooms). The openings should be a minimum of 450mm x 450mm and 0.33m2 in size. Rooflights should be between 800mm and 1,100mm from the floor at the bottom of the opening (which should normally be top opening). If you’re adding a third storey, you’ll need to make sure there’s a secure stairwell leading down to the exterior exit ramp. You have a variety of choices if your staircase rises from a space other than the corridor.
  • Maintain the stairwell fully enclosed in a corridor leading to an external door or.
  • At the bottom of the door, build a lobby to enclose the staircase. The lobby should have two exit doors, one for the front and one for the back. Fire-resistant doors and lobby walls are needed.
  • In open-plan homes, the staircase can end up in an open-plan area, necessitating the use of a sprinkler system.
  • According to fire legislation, the new floor joists in your loft conversion must have at least 30 minutes of fire safety, which means that the roofs in the buildings below will need to be re-plastered.
  • Building codes for provide a lot of fire protection, so an experienced builder should be familiar with them.
  • A fire door would need to be installed at the top or bottom of the new staircase to divide the loft space.
  • Existing doors on the ground and first floor stairwells must be fire resistant for 20 minutes and cannot be glazed (unless the glass is fire-rated).
  • On each floor of the building, mains-powered smoke alarms will be required, interconnected so that when one goes off, they all go off.

Other loft-related construction regulations

  • Beams and floors: To support the weight of the new space, new floor joists are typically needed. Extra joists would be required to meet building codes, and a structural engineer should be consulted to determine the joist separation distance required to accommodate the anticipated load weight. They should collaborate with your contractor to determine the size and grade of joists needed. The new joists would be installed alongside the current ones, spanning load-bearing walls.
  • Soundproofing: It would be essential to provide sound insulation.
  • Staircase: In addition to the fire regulations that refer to the staircase (see above), there are other staircase regulations that must be followed.
  • New walls will need to effectively support existing or new roof structures, particularly where existing supports are being removed.
  • Windows: For information on fire safety and new windows for your loft conversion, see the section above.
  • Bathroom: When constructing a bathroom, building codes governing plumbing, electricity, and ventilation must be followed.
  • Part P of the building regulations, as well as the 17th Edition Electrical Regulations, must be followed when installing new electrics. If the current unit does not have the appropriate power, it may be necessary to install a new consumer unit or additional units. Use a trained electrician for the job to ensure you get the certificate you need when it’s done — use the FMB’s find an electrician tool to do so.
  • Thermal insulation: The new room must meet the building regulations’ insulation specifications, which can be accomplished in one of two ways: cold roof insulation or warm roof insulation. Your building inspector will let you know which one you’ll need.

You must also follow the Party Wall Act 1996 if you live in a semi-detached or terraced home. Our guide to Party Wall Agreements has all the specifics.

At different times, a building control officer will inspect the job. They will give you a completion certificate after the final inspection.

What Is The Price Of Converting Your Loft?

Costs can differ greatly depending on the degree of specification you need, what you intend to do with the loft, where you live in the country, and any obstacles that might arise along the way, such as if you need planning permission.

Your final cost will also be determined by your level of participation, the design path you choose, the type of roof you have, and even your heating and energy requirements.

It’s preferable to have a general understanding of the factors that matter rather than attempting to calculate a cost using generic online guides. Loft conversions can typically start at £35,000 and can cost well into the hundreds of thousands of pounds, depending on your specific needs.

Spend some time ahead of time preparing a concise brief for your builder, including plans if necessary. As compared to a hazy calculation that could alter, this would ensure a more reliable quote.

Check your quote to see if it covers design services.

  • Sanitary ware and installation in the bathroom
  • Water tanks and chimney stacks are removed or repositioned
  • Radiators or underfloor heating are also options
  • Doors and windows
  • Is The finish is cement?
  • Finishing the flooring (carpet etc)
  • Lighting is quite important, Waht options?
  • Decoration is essential, to your tatste
  • Fees for planning
  • Fees for building inspections
  • Any roof repairs that are needed

Ask your builder what your final quote would contain so that you and your builder are both on the same page. Some quotes will provide final decoration as well as door and window hardware, while others will only cover the essentials. Remember to account for VAT as well as fees for building codes and planning permission.

Finally, providing a comprehensive brief and detailed plans ensures a more precise quote from your builder, rather than a hazy calculation that might alter.