If you’ve found you need to add more space to your home, it is best to consider how you can reconfigure your existing space before you consider building an extension. You might also want to consider converting a loft or integral or attached garage to provide the extra room you need.
When it comes to converting a loft, there is a lot that needs to be considered before you begin: from suitability and planning permission through to the various design options and of course, how much it is going to cost.
- Planning permission
- Building Regulations
- Lofts with low head height
- Ceiling joists
- Loft insulation
- Fire safety
Do I need Planning Permission for a Loft Conversion?
Unless you live in a listed building or in a conservation area, loft conversions tend to be considered Permitted Development (PD) as you are not changing the existing footprint of the building. But with PD, there will be a number of specified parameters which you will need to adhere to when it comes to your design.
However, if you plan on extending beyond the specified limits and conditions of Permitted Development, then you will need to apply for planning permission.
Do I need Building Regulations Approval?
In a word, yes. A building control surveyor will inspect your work at various stages and will issue you with a completion certificate on final inspection.
If your home is semi-detached or terraced, you’ll also need to notify your neighbour of your proposals if the works fall under the Party Wall Act requirements. For instance, if you are building in beams which will bear on the party wall(s).
Our Subscription Prices Just Got Better!
For even more advice, information and inspiration delivered straight to your door, subscribe to Homebuilding & Renovating magazine.
Who Will Design my Loft Conversion?
When it comes to designing your loft conversion, you have two main options:
Architect or Designer
You could choose to commission an architect or architectural technologist to produce drawings which you can then put out to tender.
Choosing this route means you can steer the design to create exactly what you want but bear in mind that, as this is likely to be a relatively small project, the fees are likely to be a high proportion of the overall build costs.
You will also need to hire a structural engineer.
Design and Build Company
If you would prefer an all-inclusive service (and price) then you could hand the project to a design and build contractor, who will have a designer and engineer in their team.
Design details and solutions are likely to be standardised and so you may find you have less creative flexibility.
Both options will deal with planning permission, if required, and Building Regulations approval.
Is My Loft Suitable for Conversion?
Loft Conversion Assessment
You will need to consider factors including
- available head height
- roof pitch
- roof structure
- any obstacles such as water tanks or chimney stacks
Measure from the bottom of the ridge timber to the top of the ceiling joist; the useable part of the roof should be greater than 2.2m.
The Building Regulations impose no minimum ceiling height for habitable rooms. But don’t forget to consider the stair entry to the loft space. The headroom standard for stairs of 2m applies, but this can be relaxed to 1.9m or 1.8m on the edge of a stair if necessary.
Ask your designer to clearly illustrate how much headroom there will be across the floor in the finished space.
Some people are disappointed by how much standing space they actually have, and this isn’t always easily conveyed on plans.
The higher the angle of the roof pitch, the higher the central head height is likely to be, and if dormers are used or the roof is redesigned, the floor area, and potential for comfortable headroom, can be increased.
Type of Roof Structure
Two main structures are used for roof construction — namely traditional framed type and truss section type.
The traditional framed type is often the most suitable type for attic conversions. The space can be easily, and relatively inexpensively, opened up by strengthening the rafters and adding supports as specified by a structural engineer.
For a trussed roof, you will require a greater added structural input.This will normally involve the insertion of steel beams between loadbearing walls for the new floor joists to hang on and the rafter section to be supported on — together with a steel beam at the ridge.
It is advisable to seek advice from specialist firms in this instance.
Without the roof space for water tanks and plumbing, the heating and hot water system may have to be replaced with a sealed system.
Unvented hot water cylinders make a better choice than replacing the boiler with a combi boiler, but they do take up a cupboard-sized room, which you will have to find space and budget for.
How Much Will my Loft Conversion Cost?
Your roof structure, existing available space and whether you need alterations in order to accommodate the staircase will all affect the cost of your loft conversion.
Here are some ballpark costs to give you an idea of how much it will cost.
Room in Roof Loft Conversion
A basic ‘room in roof’ loft conversion is the cheapest and could start at around £15,000. This will usually involve:
- the reinforcement of the floor
- a couple of skylights
- added insulation
- a staircase to the loft
- electrics, lighting and heating
- fire safety measures to comply with Building Regulations such as fire doors and smoke alarms.
Dormer Loft Extension
This is as the above, but with the addition of dormer windows. This will increase the useable floorspace and can be used to add head height which gives you more options when it comes to placement of the stairs.
This will cost upwards of £20,000. However the average dormer loft conversion with a double bedroom and en suite costs about £35,000–£45,000.
‘Raising the Roof’ or Changing the Roof Structure
This option is the most expensive as it requires the complex removal and rebuild of the existing roof. You will need to hire a designer, and as this type of conversion requires planning permission approval, you will need to factor in the design cost as well as the cost of the planning application.
This type of work is likely to cost upwards of £40,000.
Ready-made room options that are fabricated off-site and then craned into position are available. This option is quicker and can reduce labour costs, but costs around £55,000 for the average home.
Sponsored by Protek
What insurance do I need if I am converting my loft?
If you are carrying out loft conversion works and are managing the project yourself you should arrange conversion insurance to cover the new works and the existing structure. This is because most home insurers will exclude loss or damage whilst the property is undergoing alteration or renovation.
It’s worth discussing your project with a specialist site insurance provider like Protek as loft conversion projects can be complex and often include liability assumed under the Part Wall Act 1996.
Site insurance caters for both the existing element of the property that’s being converted and all the new conversion works that go into the process. The existing structure is usually your house — so if the property collapses while creating a new opening for example, the renovation insurance will cover it and completely replaces the requirement for buildings insurance, which is not suitable.
All the works, including any temporary works, materials, plant tools and equipment need to be covered. Public liability and employers liability is automatically included to ensure you are adequately protected.
My Loft has a Low Head Height – Can I Still Convert?
If the initial roof space inspection reveals a head height of less than 2.2m, there are two available – but costly – solutions that will require professional input.
Solution 1: Raise the Roof
This is structurally feasible, but the major problems are the high cost and getting planning permission approval. If the whole roof area needs removing, a covered scaffold structure, to protect the house from the weather during the works, would also be required.
Solution 2: Lower the Ceiling in the Room Below
This will require all the existing ceilings in question to be removed, causing much mess. With this method a plate will need to be bolted to the wall using shield anchors or rawlbolts, for the new floor joists to hang from. There is also a need for a suitable tie between the roof structure and the dwarf wall formed, to prevent the roof spreading.
Find out more about the costs and work involved for loft conversions for difficult roof constructions
Will I Need New Ceiling Joists?
The existing ceiling joists are unlikely to be adequate to take a conversion floor, so additional new joists will be required to comply with the Building Regulations.
The size and grade would have been specified by the structural engineer, who will have taken into account the span and the separation distance for a given loading.
The new joists span between load-bearing walls, and are normally raised slightly above the existing ceiling plasterwork by using spacers below the joist ends. This spacing must be sufficient to prevent any new floor joist deflection from touching the ceiling plaster below.
The new joists run alongside the existing joists. Above window and door openings, thicker timbers are used to bridge the opening, so that pressure is not put on the existing opening lintel.
Rolled steel joists (known as RSJs) are also specified to distribute the load, and in some installations are used to carry the ends of the new joists. If head height is limited, then thicker joists, more closely spaced, can be specified.
|SPONSORED: Further Reading from Econoloft Ltd – The Loft Conversion Authority
1. Is a loft conversion cost effective?
2. What type of loft conversion should I have?
3. Do I need planning permission?
What Loft Insulation Will I Need?
Your Building Control inspector will specify exactly what you require. The roof structure can be insulated in one of two main ways:
Cold Roof Loft Insulation
The most straightforward is to use a ‘cold roof’ method. This involves filling the space between the rafters with 70mm-thick slab foam insulation, ensuring that there is 50mm spacing between the roofing felt and the insulation (for ventilation via the roof and soffit vents).
In addition, 30mm slab insulation is attached to the inside of the rafters, giving a total of 100mm of insulation. The rafter thickness is often less than 120mm, so a batten may be required along each rafter to allow the 50mm spacing and the 70mm insulation.
The roof section requires 300mm of mineral wool insulation (e.g. Rockwool), or 150mm of slab foam insulation, such as Celotex.
Warm Roof Loft Insulation
This method uses 100mm Celotex insulation or similar over the rafters, and a covering capping, followed by the tile battens and tiles. This is not really a practical option unless the roof coverings have been stripped off. It could be used with a dormer, especially if it has a flat roof.
Continuity of insulation between walls and roof is required to avoid any cold bridging. The dormer walls can be insulated with 100mm Celotex between the studwork.
The internal partition walls use a 100mm quilt that will provide sound insulation. Plasterboard is attached to one side of the wall then the quilt inserted, followed by plasterboard on the other side.
Insulation is also placed between floor joists, and this is typically 100mm-thick Rockwool fibre or similar — mainly for its sound-reduction properties.
Insulating the Floor
Insulating the floor can be achieved by a mineral fibre quilt laid between the joists. Use the heavier, denser sound insulation quilt.
Insulating Party Walls
If you live in a terraced or semi-detached home, it is often necessary to insulate the party walls — both against heat loss and noise. Introducing timber studwork with mineral fibre insulation will allow you to achieve both and it can be covered with sound-rated plasterboard.
Staircase to Your Loft Extension
The ideal location for a staircase to land is in line with the roof ridge: this will make best use of the available height above the staircase.
The minimum height requirement above the pitch line is 2m, although this could be reduced to 1.9m in the centre, and 1.8m to the side of a stair.
In practice, the actual position will depend upon the layout of the floor below, and where necessary the available height can be achieved using a dormer or adding a rooflight above the staircase or, if appropriate, converting a hip roof end to a gable.
- Maximum Number of Steps: The Building Regulations specify that the maximum number of steps in a straight line is 16. This is not normally a problem, as a typical installation usually only requires 13 steps
- Step Size: The maximum step rise is 220mm, whereas the step depth or ‘going’ is a minimum of 220mm; these measurements are taken from the pitch point. The step normally has a nose that projects 16-20mm in front of the pitch line. However, the ratio of size must not exceed the maximum angle of pitch requirement of 42°. Any winders must have a minimum of 50mm at the narrowest point. The width of steps is unregulated, but in practice the winders are likely to limit the reduction in width.
- Balustrading: The height minimum is 900mm above the pitch line, and any spindles must have a separation distance that a 100mm sphere cannot pass through.
Bespoke Staircase Solutions
Sometimes a bespoke solution is required. Bespoke staircases cost much more than standard off-the-shelf models, so it pays to consider all your options.
It is also worth having the design approved by your Building Control body to ensure the staircase will comply. Ask your joiner or builder to email a copy for approval before the staircase is fabricated.
Light and Ventilation in Loft Conversions
The loft room will require a means of getting natural light and ventilation.
Rooflights for Loft conversions
The most straightforward method is to use rooflights that follow the pitch line of the roof. This type is fitted by removing the tiles and battens where the rooflight will be fitted. The rafters are cut to make way for the rooflight after suitably reinforcing the remaining rafters.
The rooflight frame is then fitted and flashings added before making good the surrounding tiling.
This type of window is the most economic, and more likely to be allowed without planning permission.
Dormers not only give natural light but can add space to a loft extension.They are particularly effective where the pitch angle is high, as the useful floor area can be increased.
The mansard type will give maximum conversion roof space because it projects the maximum available head height, thus giving a greater usable floor area. A hip to gable conversion has a similar effect.
Dormers and other similar conversions are normally installed by opening up the roof, and cutting the required specified timbers to size on site.
Adding a Bathroom in a Loft Conversion
If you are going to put a bedroom in the attic then it makes sense to try and fit in a bathroom, but do follow these tips:
- Place a shower where there is full headroom
- A bath can be tucked under the eaves
- A WC ideally needs full headroom, as does a washbasin
- A wetroom can be a space-efficient option, but needs full tanking
- Use the voids in stud walls for concealed shower and tap mixers
- Concealed cisterns in metal frames for building into studwork are ideal
- Good lighting and large wall-to-wall mirrors create the illusion of space
- Wall-mounted sanitaryware helps make a small bathroom appear more spacious
Loft Conversion Fire Safety
Ensure that the new windows are large enough and low enough to escape from:
- Egress window openings are needed to serve all first floor habitable rooms, but not bathrooms
- Openings should be at least 450mm x 450mm and at least 0.33m2 in area
- Rooflights are usually top opening — you must ensure the bottom of the opening is between 800mm and 1,100mm from the floor
Things become more complicated if your loft conversion transforms a two-storey house into a three-storey home:
- Escape windows that are over 4.5m from ground level are not viable. Instead, the Building Regs require a protected stair enclosure that leads right down to the final exterior door
- If your staircase rises from a room, rather than a hall, you have two choices:
- It can be entirely enclosed within a hallway to an external door
- The staircase can be enclosed in a lobby at the base of the stairs. The lobby will have two separate doors, to offer a choice of either a front or back route of escape. These doors and the lobby walls will need to be fire-resistant and most likely open outwards into the rooms to avoid fouling the bottom of the stairs. If the doors do not open outwards into the rooms, they will be acceptable as long as they create viable options for escape in the event of a ground floor fire
- For open plan homes, where the staircase lands in an open plan space, a sprinkler system may be the only option.
The new floor joists of your loft conversion will need to offer at least 30 minutes’ worth of fire protection, which could mean replastering the ceilings in those first floor rooms below.
The loft room will also have to be separated by a fire door, either at the top or bottom of the new stairs.
The existing doors on the stairway to both ground and first floor should be able to provide 20 minutes of fire resistance or be replaced. They can’t be glazed either (unless with fire-rated glass), so you may want to consider windows or rooflights to bring daylight to the stairwell.
Mains-powered smoke alarms should be installed on each floor of your home and interlinked so that they all sound off when one is activated. Most have a rechargeable battery as a back up that allows the supply to be extended from a lighting circuit if necessary.
Wireless, radio-linked alarms can be fitted if you can’t hardwire to the ground floor ceiling.
Read more about Part B of the Building Regulations (relating to fire safety)
Soundproofing a Loft
It’s definitely worth making an effort to reduce sound transfer between the new loft space and the floor below, as the Building Regulations standard is not very rigorous.
Sorting Out the Services
As in any successful interior scheme, different light sources should be combined, including ambient (substituting for daylight), task (reading, working) and accent (to add atmosphere) lighting.
Lighting options on sloping ceilings include downlights and track lighting. A section of flat ceiling beneath the ridge or within a dormer window is the ideal surface for downlights. Where the ridge is higher, it may be possible to suspend pendants or a track lighting system.
Ambient lighting can also be provided using floor and table lamps, providing they are on a switched lighting circuit so that they can be controlled, and ideally dimmed from the main wall switches.
To maximise energy efficiency, the roof space should be made as airtight as possible, and to counter this it is essential to introduce controlled ventilation to prevent the risk of condensation and maintain good air quality.
This means including background ventilation (airbricks and trickle vents) and rapid ventilation (via windows), plus extract ventilation in wet areas, such as bathrooms or a kitchen.
Attic bathrooms are not required to have a window providing the extract fan can provide rapid ventilation.
Extensions normally increase the heat load requirement of the house and so the boiler has to be upgraded, but a loft conversion may require little extra capacity as the space will be well insulated and can improve the overall energy efficiency of the house.
However, if a bathroom is added, a boiler upgrade may be necessary. It is a good idea to switch to an unvented system that does not require header tanks but relies on mains pressure (as long as it’s at least 1.5bar).
If you are adding a bathroom you’ll need to think about the location of existing services. Adding hot and cold water supplies is straightforward, branched off the existing plumbing system either at the boiler or from the floor below. Flexible plastic plumbing is easy to thread through the joists.
Existing soil pipes are likely to be vented above roof level and it may be possible to boss a connection into this, or into another soil pipe on the floor below. Where there is no existing soil stack you may be able to add one; otherwise, a smallbore flexible waste pipe can be used to connect to the drains.