If your answer is no, fear not, because our project checklist is here!
structural stability
The roof structure, including the floor, must be of adequate strength for use as a habitable room and this will need to be calculated by a structural engineer or specialist loft contractor to ensure compliance with building codes.
Existing roof joints may not be strong enough to use as new flooring. These are usually strengthened by adding floor joists along with the existing ceiling joists, which extend through the structural walls on the floor below.
Where headroom is limited, it will be helpful to keep any increase in the depth of the floor structure to a minimum by using shorter length joists that extend from the structural walls. In some cases where the existing roof ridge height cannot be raised for planning reasons, it may even be worth lowering existing first floor ceilings to create additional attic clearance.
Fire safety
Building regulations require that there be a safe means of escape in the event of a fire from any floor with a floor level of more than 4.5m above ground level. This is usually accomplished by creating an enclosed stairwell that will resist fire for at least 30 minutes. Typically this means upgrading the walls, floor, and ceiling of the hallway that houses the stairs, and changing or upgrading doors to provide 20 minutes of fire protection and adding automatic door closers.
An alternative and more common solution is to protect the stair enclosure at reduced performance and add an egress window, an escape window, in each habitable room in the attic, bedrooms but not bathrooms. This allows you to keep your existing doors, as long as they are equipped with automatic closers. Escape windows must have an opening clearance of at least 450mm x 450mm and be in a position where there is an acceptable escape route.
Either way, the penthouse conversion must be separated from the rest of the house by a self-closing fire door and the structure must have a 30 minute fire rating (one stud wall with 15mm plasterboard on both sides). faces is enough) and permanent wiring. (connected to hands) smoke detector.
Ventilation
New attic rooms must have a window that can be opened to provide ‘quick ventilation’ (minimum 1/20 floor area) and background ventilation through a whole house ventilation system, vents or similar ventilation ducts. Any bathroom should also be equipped with mechanical extraction.
The roof structure between new insulated sloped roofs and roofing felt must also be ventilated to prevent potentially harmful moisture buildup. This is usually achieved by leaving at least a 50mm air gap between the insulation and the underside of the roofing felt. This void must be ventilated at the eaves and ridge. Where the joists are not deep enough for 55-60mm of insulation plus a 50mm air gap, it may be necessary to add battens or use an ultra thin sheet type insulation product combined with a rigid insulation board.
When rebuilding the roof or lifting and replacing the roof covering, an alternative to adding vents is to use a breathable roof membrane. This can eliminate the need to leave the 50mm vent gap and add vents.
thermal isolation
Loft rooms must be insulated to a high standard to meet today’s fuel and energy conservation requirements. It is generally accepted that superior insulation products should be used, such as rigid urethane foam boards with a foil face, or better yet, rigid phenolic foam panels with a foil face.
To achieve the minimum requirement of a U-value of 0.3 W/m2K, it is necessary to add around 55-60mm of insulation between the joists (leaving a 50mm clearance between the top of the insulation and the bottom of the ceiling felt) plus another 25mm of insulation under the plasterboard-covered joists. This minimal thermal performance can be significantly improved by adding more insulation.
Acoustic isolation
The roof and exterior walls must meet a minimum sound insulation standard. It’s also a good idea to try to reduce sound between the new attic rooms and the floor below. Placing mineral wool insulation in the floor structure will reduce airborne sound transfer. Laying acoustical mats over the floor structure, typically made from recycled rubber, prior to laying carpet or a floating floor will reduce impact sound transfer.
stair access
A residential penthouse conversion must have a permanent access ladder. Ideally this will be a conventional ladder, however in certain circumstances a space saving ladder or permanent ladder may be acceptable.
The circulation space needed to reach and accommodate a new stair will ideally be taken from an existing hallway. Whenever possible, the new flight can repeat the main flight from the ground floor. The practical minimum width for an access corridor is 900 mm. When space must be taken from existing rooms, the space lost must be weighed against the space lost must be balanced against the space gained in the attic. Careful consideration should be given to which room you can afford to lose access space, ensuring that each room retains good proportions and is a practical and usable space.
conventional ladder
A conventional staircase leading to an attic must comply with building regulations and have steps (the horizontal part of each step) and risers (the vertical part between the steps) of no more than 220mm and a maximum slope of 42 degrees. There is no minimum width for a staircase defined by building regulations, but a width of 600-850mm is the practical minimum. There should be a minimum clearance of 2m above the stairs, however in situations where the stairs are below a sloped roof this can be reduced to 1.9m at the center point of the flight, with a minimum of 1.8 m at the edge.
There should be a landing at the top and bottom of the stairs of the same width and depth as the flight width. The doors can be installed at the edges of the upper landing, but they must open outwards (towards the attic rooms). Doors around the bottom landing can swing in any direction as long as there is at least 400mm clearance at the bottom of the flight.
space saving stairs
A space-saving staircase with alternating trends is acceptable when there is only one attic room (including a bedroom with an en-suite bathroom, as long as there is another bathroom in another part of the house).
loft stairs
A fixed loft ladder with a handrail is acceptable as long as there is only one attic room and a ladder cannot be added without disturbing other rooms.
windows
There are three options for quickly bringing light and ventilation into the roof space: gable windows, dormer windows, and skylights.
Conventional windows can be added in the gable walls, if planning permission is required, the main issues will be whether or not the window creates privacy issues due to the proximity of neighboring properties. around £700-800.
The dormer windows stand out from the line of the roof slope. By increasing the volume of the house, they constitute an extension and therefore require a building permit. A dormer will cost £7-800 and up depending on size including a double glazed window unit. A dormer window can be used to create additional loft clearance, often providing a solution to a shortage of clearance above stairs, a sitting area or for bathrooms.
Skylights are windows that are placed in line with the pitch (tilt) of the roof. Skylights can usually be inserted without the need for planning permission. A skylight can add around 200mm of clearance, enough in some cases to overcome a shortage of clearance over a stairway or seating area. A standard skylight, installed, costs between £4-500 and up depending on size.
special skylights
Skylights are available in large sizes and several can be combined to form prominent windows. Models are available that open to comply with fire exit window regulations, and others that open to form a balcony.
Where conventional skylights are not acceptable, for example in listed buildings and in conservation areas, conservation skylights may be acceptable. These are designed to mimic traditional cast iron skylights that sit flush with the roof line.
Additionally, tube lights channel light through mirrored ducts into rooms where other forms of natural lighting may be unsatisfactory.
Heating, Plumbing and Electricity
As long as the boiler has sufficient power, new radiators for attic rooms can usually be added to the existing central heating system. All water storage tanks in the existing loft will need to be moved or replaced to make room for the conversion.
When there is no room to move the tanks to another part of the loft (gravity fed systems must be higher than the highest outlet or radiator to work), an alternative is to upgrade to a pressurized (non-vented) plumbing system. modern systems that do not require header tanks.
The choice is between a combination boiler that will switch on the central heating and provide hot water on demand, or a system boiler to switch on the central heating, plus a pressurized hot water storage cylinder that can be located anywhere in the house .
New power points and lighting circuits can usually be added to existing circuits or in new circuits added to the existing consumer board. Home wiring is now covered by building codes and if existing wiring needs to be updated, this work will need to be done at the same time as the new wiring for the loft conversion.
exclusions
Mezzanine attic rooms, an open gallery covering an area of less than 50% of the floor below, have more relaxed fire regulations as long as the space is a non-living room. Loft-over-bungalow conversions are also excluded from most regulations, although the staircase must still lead directly to an exterior door.
