Loft Conversion to a 2 Storey Dwelling
Overview
If you intend to convert an existing loft space
into additional rooms you will need to apply for building
regulation approval. You may also need planning permission if you
live in a conservation area, area of outstanding natural beauty or
a listed building and/or are installing a dormer window or
rooflight. It is strongly advised that you speak with the planning
department before undertaking such work.
This guidance deals with the technical points
of building regulations which most often cause
difficulties - if you cannot find ways of dealing with them, it may
not be possible to convert your loft at all.
Latest Building Regulations Requirements
From 6 April 2007 there have been significant
changes to requirements for loft conversions. Most of the reduced
standards that have existed for a number of years have now been
removed and loft conversions to a 2 storey house are to be treated
in similar way to a new 3-storey house.
As a result more onerous conditions apply
requiring the formation of a fire resistant protected escape route
out from the loft to the dwelling’s final exit, in order to prevent
occupants been trapped in a fire.
You now cannot to rely on escape windows to make
safe escape, as it is considered that you will be able to reach the
ground floor internally via the fire protected stairway.
The upper storeys must by served by a fire
protected stairway (protected at all levels) which either:-
a. at ground floor level discharges to a hall
served by an external door, or
b. there must be at least two separate escape
routes available to an external door - separated by fire resistant
construction and fire doors.
If you have an open plan staircase it will
therefore need to be enclosed.
The protected stair enclosure should be enclosed
in a minimum 30-minute fire resisting construction to protect the
escape route for the occupants to make a safe escape.
All doors opening onto the protected stair are
to be FD20 or E20 fire resisting doors.
One concession is that there is no need to fit
self-closing devices to any fire doors.
You must ensure that the new loft access stair
is an extension of the existing stair enclosure to avoid the
creation of inner rooms. The new stair to the second floor cannot
be enclosed within a first floor habitable room such as a
bedroom.
The new stair has to continue up in the existing
stair enclosure, in which case the fire door and additional
separating structure will be at the top floor level. Alternatively
if there is only one room in the loft space, the loft stair can be
contained within the second floor room itself and a fire door
provided at the base of stair landing position, where it exits onto
the existing first floor landing.
Where the existing house is open-plan, it will
be necessary either to provide a new 30-minute fire resistant
partition with fire doors to enclose and extend the escape route to
a final exit, or provide sprinkler protection to the open-plan area
in accordance with BS9251: 2005, in conjunction with a fire
resisting partition and door (FD20 / E20) positioned to separate
the ground floor from the upper storeys. This door should be so
arranged to allow the occupants of the loft room(s) to access an
escape window at first floor level in event of a fire in the
open-plan area. Cooking facilities must, however, in all cases be
separated from the open-plan area with 30 minute fire-resisting
construction.
Rooms within the loft should be designed so that
there are no inner rooms i.e. where escape can only be made by
passing through another room, unless the inner room is a dressing
room, a bathroom, a shower room or a w.c.
Smoke Detection
Mains powered and rechargeable battery backed up
smoke detectors must be installed on each storey in accordance with
BS5839-6: 2004 – Grade D - category LD3 standard.
All detectors must be interlinked together so
that all sound even if only one is triggered and must be placed in
the circulation spaces / protected stairway within 7.5m of every
habitable room door. If, however, due to the layout of the loft
there is no circulation space, a smoke detector should be fitted in
the loft room itself.
Smoke detectors should be mains powered to a
single independent circuit on the dwellings mains consumer unit or
a single regularly used local lighting circuit. A means of
isolating power to the smoke alarms should be provided without
isolating the lighting.
Detectors are to be positioned so that they can
be reached for maintenance and testing i.e. not over stairs
etc.
If floor area of the loft exceeds 200 square
metres, the building will be considered to be a ‘large house’ and
the fire detection system will need to be improved:-
a. large dwellings of 2 storeys (excluding
basements) to have fire detection / alarm system of Grade B -
Category LD3 (BS 5839-6: 2004).
b. large dwellings of 3 or more storeys
(excluding basements) to have fire detection / alarm system of
Grade A - Category LD2 (BS 5839-6: 2004).
Upgrading of Doors
Any new door forming the protected escape route
protection will have to be a FD20 / E20 fire-resistant door fitted
in an appropriate frame as recommended by the fire door
manufacturer. Intumescent seals may also have to be fitted to the
frame or door edges as recommended by the door manufacturer to
ensure it achieves the FD20 / E20 rating. You will need to check
the installation recommendations on purchase of your fire doors, if
in doubt - order the doors with the intumescent seals fitted.
Existing doors to all rooms (other than a
bathroom, shower-room or w.c.) on the escape route need to be
replaced with FD20 / E20 fire doors. This might involve the removal
and replacement of door frames to accommodate the thicker fire
doors and to achieve the appropriate fire rating standard.
Similarly, intumescent seals may also have to be fitted as
previously mentioned above.
If you wish to consider upgrading the existing
doors e.g. they may be of historically or architectural merit, you
will be required to upgrade them to an approved method supported by
appropriate manufacturers test data and confirmation that the doors
meet their upgradeability standards. Note: not all doors can be
upgraded as they may be too thin or the infill panels and fixings
may be inadequate, so consider the implications carefully if you
choose this option.
There is no requirement for these fire doors to
have self-closers fitted, but if you are a builder or architect you
are advised to inform your client of the importance of managing
these fire doors and keeping them shut whenever possible.
Door hinges may need changing to steel hinges as
all hinges on fire doors should have a minimum melting point of 800
degrees C (brass and aluminium hinges will fail prematurely).
Any door glazing needs to be 30 minute
fire-resistant and of appropriate safety glazing, fixed in
accordance with the glazing manufacturer’s requirements to ensure
the fire-rating is achieved. This is particularly important if you
intend to upgrade existing doors as glazing rebates / beads will
likely require improvement or replacement.
Protected Escape Route
You need 30-minute fire protection to the escape
routes and the walls forming the protected routes need to be
carefully checked to see if they will achieve the required fire
rating. Masonry walls will achieve the standard, but if they are of
stud construction you will be expected to prove that they provide
30 minutes fire-resistance; for instance lath and plaster walls may
achieve only approximately 20 minutes fire-resistance and will
require upgrading. All new walls will have to be suitably
constructed to a full 30-minute fire resistant standard.
Ensure all pathways that are likely to bridge
the escape route’s fire protection are suitably fire stopped or
fire protected (e.g. tops of walls / around services / drainage
pipes /air vents etc.)
Any glazing that exists in the walls forming the
escape route enclosure must be at least 1.1m above the floor level
or stair pitch line and changed to 30-minute fire-resistant glass,
such as Georgian wired safety glass. If there are existing glazing
frames to be adapted, it is likely that they will need replacing to
ensure the new fire resisting glass is properly installed in
accordance with the manufacturer’s recommendations to achieve the
30-minute fire rating.
You must also ensure that any roof spaces that
remain over the top of the fire resistant walls are extended up to
the underside of the roof covering or, alternatively, a new half
hour fire resistant ceiling is provided.
The new floor to the loft conversion must be of
30-minute fire-resistant construction i.e. 30 minutes load bearing
capacity, 30 minutes integrity and 30 minutes insulation
(30/30/30). If you are retaining your existing ceilings, which are
usually suspended from the new floor construction, you will have to
upgrade any sub-standard ceiling construction to ensure the new
floor achieves this required rating.
The existing first floor construction would also
normally have to be upgraded to a full 30-minute standard
construction (which could mean under drawing the existing
ceilings). However this can be avoided if the existing floor
construction (separating rooms only) is of a ‘modified 30-minute
standard’ i.e. reduced performance of 30/15/15, (e.g. 12.5mm
plasterboard with joints taped or 9.5mm plasterboard and skim or
lath and plaster with 16mm plaster finish over laths), and the
following conditions are satisfied:
a. Only 1 storey is to be added and the storey
contains no more than 2 rooms; and
b. The total storey floor area is not more than
50 square metres; and
c. Floors which separate rooms from the
protected escape route / circulation spaces are upgraded to or
achieve a full 30-minute fire resistant standard.
Stairs and Headroom Requirements
A fixed staircase complying with approved
document K must be installed to form permanent safe access into the
converted space.
You must have a minimum of 2 metres headroom
over the stairs and landings, although a slightly reduced headroom
standard of 1.9 metres (to centre-line of stair) can be applied to
the stairs where the flight is parallel to the roof slope.
Be aware that the space and headroom currently
available in the roof space will be considerably reduced by the
provision of a new structural floor, the fixed staircase, stair
enclosures or guarding and provision of insulation to walls and
ceilings etc. You should ensure that the finished space and
headroom will make a loft conversion viable before continuing down
the design process.
Insulation Requirements
Walls, including ashlar walls and dormer cheek walls need to
achieve an area-weighted average U-value of
0.28W/m2K.
A pitched roof, including pitched dormer roof will need to
achieve a U-value of 0.16W/m2K if insulation is
installed at ceiling level, or 0.18W/m2K if insulation
is installed at rafter level.
Flat roofs, including flat dormer roofs, need to achieve a
U-value of 0.18W/m2K.
The floor construction will need to be insulated to prevent
excessive sound transmission to and from rooms below.
Other Considerations
Modern houses with trussed rafter roofs are
usually unsuitable for loft conversions, as the inner members of
the truss cannot normally be removed. You are advised to seek
advice of a suitably qualified professional to establish whether or
not the roof structure can be altered to accommodate the planned
accommodation.
The existing ceiling joists in the roof will
almost certainly be inadequate for use as floor joists. In most
cases it is possible to install new floor joists and support beams
between the existing ceiling joists to maximise the headroom
available. You are advised to seek professional guidance and
provide calculations for any support beams you intend to provide to
support the floor.
The new rooms will need to be fully insulated to
prevent excessive heat loss and sound transmission. While there are
many ways of achieving this, we would recommend that you check your
chosen method with your Building Control Surveyor before any
insulation is installed. Be advised that the provision of this
insulation will often reduce the headroom to the existing loft
space.
You should be aware that the above is guidance
only, and there are many other areas where the building regulations
impose requirements relating to loft conversions.
You are strongly advised due to the complex
nature of these types of projects that you make a full plans
application, where the majority of the problems can be resolved
before you start the works.
This webpage was updated on
1/31/2012