Beta Design Consultants include architectural and structural engineers who can advise Clients on common design considerations when converting a loft:

  • Ceiling height and available headroom following the conversion
  • Access and ideal location of stairs
  • Services and location of boiler
  • Lighting issues and positioning of skylights if allowed (some Conservation Areas place restrictions on loft conversions and if they allow them some restrictions would apply to skylights)
  • Planning permission vs permitted development
  • Building regulations related to floor strength, insulation, ventilation and fire escapes

We work with our Clients to conduct site surveys, design meetings and propose to them designs to overcome these issues. A loft conversion can be life changing and a cost effective solution to lack of space and in some cases can be an alternative to moving house.

Is my property suitable for a loft conversion?

Not all lofts are suitable for a loft conversion. Before going too far into planning you’re your loft conversion project, we suggest that we carry out a brief survey to checks the following:

  • Roof structure: a traditional purlin and rafter roof would be different from a trussed roof and this has implications on how to add a loft and how to accommodate the additional loft loading.
  • Headroom: the available height within the lofts space would be a deciding factor in the loft conversion feasibility. The minimum height for a traditional roof is 2.2 to 2.4 meters and the minimum height for a modern trussed roof is 2.4 to 2.6 meters. We have worked with shallower lofts where the headroom was less (in one case only 1.85m). The only option in such cases would be to lower the ceiling of the level below, which would obviously have impact on schedule and cost.
  • Space: the available layout, size and footprint would decide if the loft space is large enough to provide a usable and habitable room.
  • Chimneys and services: these need to be considered and the design needs to take into consideration their location and impact of removing the chimneys breast or the stack.
  • Felt: some lofts have felt under the tiles while others don’t have felt and the back of the roof tiles and the battens can be seen.
  • Neighbourhood: a quick check would be to look around and see what neighbours have done and what type of loft conversion they carried out. We have only once carried out a loft conversion in a street that did not have lofts already converted. We have carried out loft conversions even in conservation areas and to very shallow roofs. However, if many properties in your street are already converted, this would be a sign that a conversion is possible and practical.

What type of loft conversion shall I consider?

After deciding that a loft conversion is feasible, we proceed to assessing what kind of loft conversion you could have. This will be based on the following:

  • The type of your property and the shape of its roof
  • The type of loft that you intend to have
  • The budget and construction schedule that you have in mind

There are three types of loft conversions to consider.

  1. Internal loft conversions: these are the cheapest and require minimum building intervention. They are the most cost effective as very little alterations to the roof space are needed. Additions include windows set into the existing roof slope, insulation and strengthening of the floor.
  2. Dormer loft conversions: these are the most common because of the additional space they provide with relatively simple building works. Dormers are added to increase the volume of the roof space while providing full head height. They are usually added to the rear, but subject to planning permission, they can be added to the side or front of your property. Following a loft conversion, the additional space can be used as an additional bedroom or two, a study or home office, a separate bathroom or a nursery. Sometimes an en-suite or separate dressing room can be attached to a master bedroom. We highly recommend that en-suite are located above existing bathroom or towards the boundary to allow easy integration of services and routing of foul water drain pipes.
    • Single Dormer
    • These are favoured by planners in conservation areas. If permitted, two of these can be used to increase space and add symmetry.
    • Side Dormer
    • A side dormer is often used to increase head height for houses with a hipped roof, where access to the loft is located under that hip.
    • Hip-to-Gable
    • These are usually suitable for end of terrace, semi-detached or detached properties. They Involve one or more of the hips being replaced with a gable wall. The roof is then extended over these gables to add extra space with full headroom.
    • Full Width Dormer
    • This type of loft conversion will really maximise space and achieve a completely different feel to any other type of loft space.
    • L-Shape Dormer
    • These are only suitable on certain properties such as Victorian properties with an outrigger to the rear. The L-Shape Dormer provides a significant amount of additional space. It involves constructing two dormers – one over the roof of the main house and a second above the outrigger. The two dormers meet to form a right angled ‘L’ shape (hence the name). The advantage of an L-Shape conversion is that it allows the Client to almost replicate the first floor in terms of space and design. It gives the possibility for three new rooms and no other type of loft conversion will give you as much additional space.
  3. Full removal lofts: these give the most flexibility but are the most complex and expensive as they require full removal and full rebuild.
    • Mansard conversions
    • This type of loft conversion involves one or both slopes of the roof being replaced with a new structure with very steep sloping sides (almost as steep as the walls). An almost flat roof is placed over the top. This design is used where the original roof had little or no headroom and creates sufficient volume for an additional storey. Mansard conversions normally require planning permission and are very common in some London suburbs such as Fulham, Chelsea, Hammersmith and Chiswick.
    • Pre-fabricated loft
    • Where vertical space inside a roof is limited, the existing roof truss can be replaced with a larger one. New trusses labelled “Room in the roof” trusses can be craned in place to form the shell. The roof can then be constructed around them. Living without a roof for over a month is no fun! But a pre-fabricated unit can be watertight in a couple of days.

What is the cost of loft conversion?

What you pay for a loft conversion depends on the type you undertake. At current prices (August 2015) we would offer the following guide price per square meter. Note this excludes VAT and fees and are based on medium level finish. Subtract 20% for basic finish and add 30% for high end finish.

  • Simple rooflight conversion — £1,200 per sqm
  • Dormer conversion — £1,800 per sqm measured (excludes eaves area behind the dwarf wall)
  • New Boiler may cost between £3000 and £5,500 including installation
  • Bathrooms range from £4,500 to £8,000 including tiling
  • Decorating can cost £75 per square meter for plastering or dry lining and paint.
  • Flooring can cost £24 to £60 per square meter depending on finished floor choice

What are the professional fees for a loft conversion?

  • Architectural Design Fees — a typical £40,000 to £60,000 loft conversion would be in the region of £1,200 to £2,400 for planning drawings.
  • Structural Engineer’s Design Fees — £1200 to £1,800
  • Building Regulations Package Fees — approximately £400 to £700 (depends on area and addition of toilet/en-suite)
  • Planning and certificate of lawful development fees — If you cannot carry out your loft conversion under Permitted Development Rights then a householder planning application costs £230. If you’re using your Permitted Development Rights, we advise you obtain a certificate of lawful development for £123. This certificate takes away any uncertainty and you can produce it when selling the property
  • Building Control fees — in the region of £900 to £1,200 (depends on addition of en-suite or not)
  • Party wall arrangement fees — Budget about £900.00 per dissenting neighbour

What are the planning requirements for loft conversions?

Homeowners can extend the roof space by up to 50 cubic metres for detached properties and by up to 40 m3 for terraced housing under Permitted Development Rights. This is measured from the original house roof. This can save the hassle of gaining planning permission, but there are strict limits to follow. For example, no additions are allowed at the main elevation beyond the plane of the existing roof slope. Also, materials for the loft conversion have to be similar in appearance to the existing house.

Permitted Development Rights are removed for loft conversions exceeding the 40 m3 to 50 m3 space allowance, in conservation areas and in other designated zones. A full planning applications is needed in such circumstances. Some conservation areas are more strict than others and reference shall be made to the guidance of the local authority planning department to establish the rules for each area.

Do I need Building Control for my loft conversion?

Loft conversions always need approval from Building Control to ensure their compliance with the Building Regulations (irrespective of whether they need planning permission). To comply with Building Regulations, either the local authority or an approved independent inspector needs to be informed of the intended works. They can be notified using the Building Notice route (only 48 hours notice) or the Full Plans route (minimum six weeks notice). It is advisable to follow the Full Plans application approach and have a detailed building regulations package presented with the application so any comments can be made prior to the works start. This would ensure that the scheme is approved before a builder is appointed. This provides cost overruns and schedule certainty. Comments made by inspectors could lead to re-work, changes and unexpected works and these cause delays and avoidable cost increases. Having an approved design will take much of the risk out of the work and also mean the builder has a chance to give you a fixed quotation, rather than an estimate.

The Building Control officer (from the council or from an independent approved inspector) will inspect the work at various stages. On the final inspection they should issue you with a completion certificate. We advise Clients to keep a retention of the builder’s payment and not settle final accounts until the certificate is issued. Suggested retention is 5% but this needs to be agreed in advance with the builder to avoid dispute.

What is the implication of the Party Wall Act on my loft conversion?

If your house is semi-detached or terraced then as a client, you are responsible for notifying your neighbour(s) of your proposals. This requirement usually falls under the Party Wall Act 1996. Details such as building up the party wall, inserting padstones in the party wall, works to the party wall, have to be shared with neighbours formally. They need to approve the works prior to the start otherwise, you could be found guilty of not complying with the law. If they “dissent”, then they have the right to appoint a Party Wall Surveyor and as a Building Owner, you have to pay for the services of the Adjoining Owner’s Party Wall Surveyor (as well as your own Surveyor).

What are my responsibilities as a Client?

The client has a big responsibility and a great role in ensuring that their project is executed safely, legally within a reasonable time and to their budget. From April 2015, Under the Construction (Design and Management) Regulations 2015, homeowners are now responsible for safety on their building projects – big or small. All projects will require a health and safety plan and the Client will be required to maintain and manage that plan.

  • Budget: The Client is ultimately responsible for properly budgeting and controlling the finance for the project.
  • Builder Competence: Appointing a competent contractor to carry out the works. Failure to do so could jeopardize the property safety, endanger lives and cause cost and schedule over-runs.
  • Appointing suitably qualified professionals to deal with all the various design stages (Architect, Engineers, Party Wall Surveyor).
  • Obtaining Planning Permission: The client should either obtain permits and permissions or delegate this to their Agent (the Architect/Planning Consultant). This includes the planning approval at the planning stage whether it is via the permitted development route or the full planning application route.
  • Building Control Compliance: The client should notify building control prior to the start of the works (either from the Local Authority BC or by appointing an independent inspector).
  • Obtaining Party Wall Aware: The client should ensure that an award is in place prior to the start of the works. Failure to do so would be a breach of the Party Wall Act that could lead to a legal dispute and to easily avoidable costs and delays.
  • Insurance: The client has a responsibility to protect their asset during the carrying out of the building works so it is important that they inform their building insurance provider and seek suitable insurance to cover risks during the execution depending on the type of works being undertaken.


Why do I need a Structural Engineer for my loft design?

The existing roof of a standard property is designed to keep out the rain and snow and to cope with light loft storage loading. The loft conversion will lead to the floor being used for normal domestic loading which can be significantly higher that storage loads. Strictly speaking, the occupied loft should be designed for nearly twice as much loading as the loft space and in most cases, the bottom chords of trussed systems or the existing loft joists would not be strong enough for this different loading. A new floor structure will be required. Just to add another complication, the triangulation offered in traditional roofs makes the roof top chords act with the bottom chords along with the braces to resist loads (triangular action). This triangulation is lost when the back rafters are cut, braces are removed and roof shape is altered. So the roof will also require structural support. It is usually also the case that structural elements will need to be altered to allow for circulation within the room, to add roof windows and to add stairs. All of this would required input from a Structural Engineer to design structural members that allow for wind and snow on the roof, domestic loading on the loft floor and support around openings such as skylights and stairs.

Roofs can generally be divided into two types.

  • Trussed Rafter Roofs — These have been common since the 1970s and they are difficult to convert due to the shape of the roof and difficulty in readily changing their configuration.. Roof trusses are complex pieces of engineering but our Structural Engineers would be able to advise on how to convert them if this is feasible. We usually design conversions for this type of roof using steel beams, flitch beams or timber beams to provide support to the new floor and to strengthen the rafters. This allows the bracing sections of the trusses to be cut out to create a clear floor area. It is very important to maintain the lateral stability of the roof following removal of the triangular action of the truss.
  • Traditional Roofs — These are made up from a series of rafters and purlins spanning between load bearing walls. These roofs are common in most period properties and the housing stock built before the 1970s. They are less complicated to convert than Trussed Rafter Roofs. However, steel beams or flitch beams are often required to provide support to the new floor structure and the existing purlins. Our Structural Engineers would design the floor beams, the ridge beam, any cranked frames required and ensure lateral stability of the roof is maintained.


How is the loft accesses and how are the stairs designed?

The design of the staircase can be critical to ensure good access to the new loft. If there is enough headroom and space, it is best to continue the existing stairs to reach the loft. This saves space and gives a feeling of continuity within the home. Alternatively part of a bedroom or bathroom will have to be partitioned off to accommodate the new staircase. Wherever the stairs are installed it should be designed in accordance with the following guidance:

  • Fire Precautions
  • The stairs form the escape route in the event of fire. When converting the loft it is important to install mains-powered, interlinked smoke detectors in the hall and/or the landing areas of every floor. The most dangerous fires generally occur at night when everyone is asleep so it is crucial that the escape route is designed to resist fire for the specified duration and that fire doors are installed in all rooms leading to the fire escape route.
  • Escape windows
  • Windows should be large enough to allow people to escape or be rescued through them. They need to have a clear opening area of at least 0.33m2 and a clear width of at least 450mm. The bottom of the opening should be no more than 1100mm above floor level and they should allow people to escape to a place free from danger. Escape windows need to be fitted with escape hinges that allow the window to fully open. Some of the standard hinges fitted to UPVC windows do not achieve this. It is wise to check this with your glazing supplier.
  • Two Storey Dwellings Fire Precautions (following conversion)
  • The Building Regulations Document B (Fire) requirements for fire precautions in two storey housing are quite simple (e.g. a single level property that becomes two level after a roof conversion). If escape is not possible via the stairs, a person could jump or be rescued from a first floor window. If the loft is for a bungalow, it is required to have mains-powered interlinked smoke detection at ground and first floor level and all habitable rooms at first floor level shall have an escape window.
  • Three Storey Dwellings Fire Precautions (following conversion)
  • This applies to most two period properties that are converted at the loft level to create a third floor. The Building Regulations require a more detailed approach to ensure fire safety. Mains-operated interlinked smoke detectors need to be fitted. Due to the height of the new loft floor, escaping through the windows would not be easy so the only safe way out is via the stairs. It is therefore vital that the stairs are protected from fire. To protect the stairs all of the doors that open onto the stairs need to be half hour fire doors and the stairs should discharge into a hall with a door direct to the outside. Alternatively, the stairs should deliver into a space with access to two external doors, separated from each other by fire resisting construction and fire doors. Generally, unless a sprinkler system or alternative escape stairway is provided, stairs cannot discharge into other rooms in three storey properties.
  • Four Storey Dwellings Fire Precautions (following conversion)
  • When a three storey property is converted, the requirements for fire protection become more complicated. Careful design and planning is required to ensure that fire risks are minimised. You are likely to need to install a sprinkler system or a second escape stairway. We have worked with clients converting three-storey townhouses in a conservation area and would be happy to assist our Clients meet the fire protection requirements for this type of project as specialist design considerations would be required.


Would it always be possible to add a bathroom or an en-suite in the loft conversion?

Including a bath or shower room in the loft conversion would add a lot of value to the new space. The best place for this is generally directly above your existing bathroom. This would ensure that the builder could easily connect into the existing drainage and water supplies without the need for excessive pipework. Any bath or shower room will also need to be fitted with an extractor fan to improve ventilation. We work with our Clients to decide the location of any bathrooms at an early stage in the space planning process. There are few considerations:

  • The shower would need full headroom (at least 1.9m)
  • The washbasin would need full headroom (at least 1.9m)
  • The toilet would ideally need full headroom but this can be slightly reduced headroom
  • A bath does not need full headroom and can therefore be positions in reduced headroom areas
  • A wet room can be a space-efficient option, but needs full tanking. All joints should be hot-welded
  • Voids in stud/dwarf walls can be used for concealed shower and tap mixers
  • Concealed cisterns in metal frames can also be hidden into studwork but coordination between the plumber and the carpenter is key to avoid rework
  • Good lighting and large mirrors create the illusion of space
  • When sanitaryware are mounted on walls, the floor would make a small bathroom look spacious


Where do I need to install the thermal insulation?

A high level of insulation is required in the loft space to meet regulations, conserve energy and reduce CO2 emissions related to low energy efficiency. High performance insulation boards (PIR rigid boards) are inserted in between and below the rafters. Unless the roof has a breathable felt, an air gap of 50mm is required above the insulation to ensure effective ventilation to prevent the build-up of condensation.

What are the other ventilation requirements?

All habitable rooms will need to be ventilated to ensure the supply of fresh air, the removal of CO2, the supply of air to burning appliances, the discharge of excess heat and moisture. This is achieved by providing an opening window or roof light equivalent to 1/20th of the floor area of the room with a trickle vent at high level. All new windows must be fitted with highly efficient double-glazed units. In bath or shower rooms an extractor fan should be fitted. Rooms without opening windows require extractor fans that are triggered by the light switch with overrun timers. This allows the fan to remain on after the light is switched off (to keep the supply of fresh air and get rid of excess heat and humidity).

Is sound insulation required?

We highly recommend the installation sound proofing quilts or layers to control noise and vibration through the walls and floors around bedrooms. Options include placing 100mm of sound deadening quilt in the floor void and in the partitions around the bedrooms. Another option is the use of a combination of sound-proof gypsum boards with acoustic floor underlays. Resilient bars are also used on walls and floors. We provide advice to our clients on sound insulation requirements. This is particularly useful for semi-detached and terraced property to upgrade the acoustic properties of the Party Wall so that sound transmission to and from the neighbours is reduced.

What is the best solution for heating in the loft?

The best and most effective way to provide heating at the loft level, would be to extend the existing central heating system. This may mean that the current boiler does not have adequate capacity to support the extra demand from new radiators or from new shower. If it is not possible to expand the capacity of the existing boiler or replace the boiler, an alternative heating method could be the use of electric panel heaters although these are less efficient and end up costing more on the long run.

What is the best way to connect electricity to the loft?

A new loft would have require electrical alterations and in some cases, it could be possible to extend existing electrical system using the existing circuits. In other cases, new circuits or a new distribution board will be required. Building Regulations required that a competent electrician is used who can issue BS7671 test certificates when the installation is completed. This is required before Building Regulations Completion Certificate can be issued.

What are the options for lighting?

The lighting needs to be planned to maximize use of natural light and use artificial lighting efficiently. A successful lighting design shall combine different artificial light sources and these include:

  • Ambient lighting which would substitute for daylight
  • Task lighting which is required for specific tasks such as reading and working in a home office
  • Accent lighting to add atmosphere for example to corners, en-suites or to the landing

Good lighting options on sloping ceilings include down lights and track lighting. A section of flat ceiling beneath the ridge or within a dormer window is the ideal surface for down lights. Where the ridge is higher, it may be possible to suspend pendants or use a track lighting system. Ambient lighting can be achieved with 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.

What is the most crucial step in a loft conversion?

In our opinion, the key activity to the success of any project is the planning. Good planning means you need to have detailed design, based on a detailed survey and developed in enough detail to ensure a realistic budget, and an accurate cost.

A successful loft conversion adds extra space value to a property. However, a poorly designed loft may cost more than the added property’s value and in some cases compromise the safety and structural integrity of a property. We have previously mentioned the role and responsibilities of the Client and we strongly recommend that these are read carefully. We have inspected many properties due to owners complaints of vibrations, noise transmission, roof spread, bulging walls, cracks at first floor, cracks at ground floor, and in many cases the refusal of inspectors to sing off the works. Most of these issues could have been avoided if proper design was undertaken prior to the appointment of the builder. Sadly, many loft conversion companies are competing fiercely, claiming to be design and build companies but they outsource the design and try to impose a standard design on all projects to maximize their profits. This could also result in a loft that is different to the originally envisaged one by the Client.

There are many elements that need to be considered when planning a loft conversion and a bespoke loft would require a properly thought out design solution. We hope that the information above can assist clients in planning and as a result reduce the hassle and stress associated with loft building works. If there is any issue that requires professional design input, our Architectural and Structural Engineers would be happy to assist.