The answer is YES if:
Or if you plan to:
This advice refers to houses. Check the Planning Portal for flats and other buildings. Contact your local planning authority if in any doubt.
Unless the conversion is for lightweight storage only and accessed by a retractable or removable ladder, the answer is YES.
The regulations will be applied to ensure, for example:
It is recommended that you contact Building Control to discuss your proposal and for further advice. You must also find out whether work you intend to carry out falls within The Party Wall etc. Act 1996.
Never cut or remove any structural roof timbers such as rafters, purlins, struts or trussed-rafter components without the advice of a structural engineer.
Any timber used for structural purposes must be strength-graded. Strength-graded timber has a stamp, usually containing one of the following markings: C16, C24 or TR26. Unmarked timber is unlikely to have been strength-graded and is not suitable for structural use.
Information on grade stamps for strength-graded timber is available in Timber Trade Topic Strength-grading.
Even if the loft was previously used for light storage, you will almost certainly have to strengthen the ceiling joists in the loft floor. You can do this by adding larger and stronger timber floor joists between the existing ceiling joists. Support them on the existing walls if they are strong enough, or add extra timber support beams if necessary. A professionally designed loft conversion plan that complies with building regulations will be needed. Check with a structural engineer.
Building regulations require 30-minute fire resistant floors for loft conversions in homes of two or more storeys.
New floor joists will need support. This can be achieved either from an existing wall, which will need to continue all the way down through the house to a foundation, or by an adequate intermediate support, such as steel or timber beams. It is particularly important to assess the structural integrity of older properties and houses with rooms knocked through on lower storeys.
In some cases, the proposed increase in load could require underpinning of the foundations. Check with a structural engineer or your building control body.
There are rules about where and how much a structural timber member can be notched or drilled for wiring and pipework, as even a small amount of drilling or notching can weaken the timber significantly. Holes or notches should not be cut in any rafters, purlins or engineered timber joists unless justified by the structural engineer. Take advice from a structural engineer and your local building inspector. Engineered products, such as I-joists may have drilling positions marked. Follow manufacturer’s instructions.
Bats and bat roosts are protected by law. If there are bats living in a roof, they cannot be disturbed or removed. If you see bats or bat droppings in the loft, you must notify the local Statutory Nature Conservation Organisation (see Further information and advice) to seek advice before work starts.
Building Regulations apply, such as:
The main types of timber staircase you could use for a habitable loft conversion are conventional, spiral and alternating tread.
Retractable ladders are not acceptable for habitable rooms in the roof because they don’t provide constant access and means of escape.
Spiral stairs and alternating tread stairs are only allowed to access one habitable room (as well as a bathroom and/or toilet in the case of alternating tread stairs, as long as it isn’t the only toilet in the building).
The opening for new stairs is normally formed by cutting away some of the ceiling joists between the existing loft-space and the floor below. As these joists support the existing ceiling and restrain the pitched roof from spreading, you must provide replacement support, such as timber “trimmers” around the opening. These will probably be at least two timbers fixed together (double trimmer) to ensure the load is transferred to the remaining timbers.
Not all the guidance in the Building Regulations is compulsory for sound transmission, but you may need to comply with Approved Document E if any additional work is required to meet the standard in the existing property.
Part L1B of the Building Regulations requires a target C rating (or U-value of 1.6) in England and Wales, though higher-rated windows are widely available. See Timber Trade Topic No. 2 Wood Windows.
Factory-finished timber window frames are a high quality solution. They may cost a little more than PVC-u, but will last up to twice as long, only need recoating every 8-10 years, and are much more environmentally-friendly.
Additional fire protection may be necessary in the existing parts of the house. For example, a typical loft conversion to a two-storey house will require new fire-resisting doors, and sometimes partitions, to protect the stairway, as it is too dangerous to escape via windows from floors above first floor level.
Fire doors are life-critical. So it makes sense to use certified products. Certification schemes, like the BWF-CERTIFIRE Fire Door and Doorset Scheme and BM TRADA’s Q-Mark Fire Door Scheme, ensure doorsets are fit for purpose. See Timber Trade Topic No. 3 Fire doors & doorsets.
Mains powered, interlinked smoke alarms are also required within the stairway at each level; and you may need to upgrade the fire protection to some parts of the structure of the house, such as the floors, where building regulations require 30-minute fire resistant floors for loft conversions in homes of two or more storeys. Consult Approved Document B (fire safety).
Building regulations require a minimum 270mm of insulation in the void between the floor joists (see adding larger, stronger joists above).
You can achieve acceptable sound insulation by using a wood-based board, such as plywood or 22mm tongued and grooved chipboard, weighing more than 15kg/m2 for the floor surface. With a terraced or semi-detached house, the building control body may also ask for improvements to the sound insulation between the converted loft and the neighbour’s loft.
A timber floor makes sense, as it is durable, easy to keep clean and good-looking. If you are laying a decorative timber floor, use an acoustic underlay. See Timber Trade Topic No. 15 Flooring for more information.
You should insulate your loft by insulating the roof itself rather than, or as well as, the loft floor. Use rigid insulation boards between the roof rafters, cut so they fit snugly between the rafters. They can then be covered by plasterboard, or timber panelling. Rafters aren’t usually very deep, so to get the best performance, you may have to insulate over them as well, using insulated plasterboard. If there isn’t room to do this, make sure you use the highest performance insulation board.
As well as adding character to a room, wood panelling can improve thermal and acoustic insulation and mask defects.
Many species are suitable, but pine and spruce are the most popular and are also available in a variety of pre-finished stains and finishes. Boards come tongued and grooved in a range of sizes and decorative profiles with thicknesses from approx. 7mm to 25mm. Boards thicker than 12mm provide additional structural strength.
For best results use timber manufactured from higher grades and kiln dried to 8-12%.
On stud walls and unplastered ceilings, the panelling can be nailed direct to the studs or joists.
Otherwise, 22 x 38mm sawn battens provide an easy surface on which to nail the panelling and also form a flat base (fig 1).
Pack out any substantial irregularities under the battens. Use ‘secret nailing’: drive the nails diagonally through the tongue of each board (fig 2). Only the first and last boards require nailing through the face. Punch these home and fill with wood filler.
Don’t forget to allow an expansion gap around the perimeter of the panelling, particularly across the width of the boards. Use skirting boards and moulded trims to hide these gaps (fig 3).
Sound insulation should also be considered between walls and floors in order to prevent noise transmission between floors or to an adjoining neighbour’s house.
Pre-finished panelling systems are becoming increasingly available. Designed for accurate and rapid installation, they also avoid the need for on-site finishing.
Loft conversion project guide, Construction Products Association
No. 2 Wood windows
For more information on staircases and fire doors, visit bwf.org.uk
Timber is the most sustainable mainstream building product. It is naturally renewable. Over 90% of timber used in UK construction comes from Europe, where more trees are grown than harvested (source: TTF Statistical Review 2016).
Softwood and temperate hardwood forests in Scandinavia, Europe, Canada and North America are stable or growing. Growing forests act as carbon sinks; wood products act as carbon stores.
Ask for PEFC or FSC Chain of Custody certification.
See Wood Campus RIBA CPD module Procuring Sustainable Timber for more on timber certification and sustainability and government requirements.