The Foundry Architects

DESIGN AND SPACE PLANNING

The typical garage is long and thin-not necessarily the ideal shape for your new room! You could consider using stud or block walling to convert that long shape into two spaces. The additional (smaller) room can be used as a toilet, shower, or perhaps a storage space.

PLANNING PERMISSION/CERTIFICATE OF LAWFUL DEVELOPMENT

If your proposed works are solely internal for your garage conversion, planning permission is not needed. However, if you live in a listed building or a Conservation Area, planning permission may be required for even minor modifications. If you are unsure of which category your garage may fall into call up your Local Authority Planning department for free advice.

BUILDING REGULATIONS

Converting your garage into a habitable room will mean complying with building regulations, including delivery of a building notice to your council. Building regulations apply to ventilation, moisture proofing, insulation, fireproofing, escape routes, and structural soundness. Dividing up the garage means a new room is created, which is subject to a set of building regulations that require an escape route and ventilation separate from the main room. Bear in mind before a completion certificate can be given by your Local Authority Building Control inspector, they will want to visually inspect windows, doors, fireproofing and foundations.

INSULATION AND DAMPPROOFING

Insulation is assessed in terms of U values: the measure of the rate of heat escape, in watts, from a square metre of the material in an hour. Each element of your garage will need to achieve these values. Window manufacturers will give the U value as part of the specification of the windows.

Damp proofing will be necessary in the walls and floor. Many garages will already have a damp proof course in the walls, but make sure to verify this. The floor will need to be damp proofed by laying a damp proof membrane at the same time the floor is remade.

PLUMBING AND WIRING

Survey your plumbing and wiring both in your house and garage. If you are planning on installing a sink or new toilet, locate where the main outflows for water and the soil outflow are.

Check the garage’s walls and ceiling for wiring. Rewiring the garage for lights and electric radiators will place additional strain on the household mains, may require the installation of a separate consumer unit.

FLOORING

Although the existing garage floor will be strong enough, you will need damp proofing and insulation to meet building regulations. You can opt for either a new concrete or timber floor.A concrete floor can be created and a damp proof membrane added between the two layers. Insulation is also added under the new floor, but sometimes requires a separation layer to prevent a chemical reaction with the damp proofing. A raised timber floor may also be built over the existing floor, with damp proofing laid under the timber and insulation between the joists and the timbers of the floor. Note, however, that fire regulations may require a step in a raised timber floor at doorways to prevent fire spreading along the floorboards.

WALLS

External walls must meet requirements in terms of moisture-proofing and insulation. If the garage is integral to the house, the exterior walls will usually meet building regulations. Otherwise consider a secondary block wall, or a stud wall, inside the existing exterior wall behind which insulation and power- and water lines can be placed.

Interior walls between rooms will also need to meet building regulations’ requirements for fireproofing. This can mean one or two layers of fireproof plasterboard on stud walls (which is unnecessary for block walls). Please note that doors through interior walls also need to be fireproof, with a 30-minute rating.

WINDOWS AND DOORS

A second room in the conversion will require ventilation to meet building regulations, as well as an escape route to meet fire regulations. Building regulations require a window 1/20 the floor area of the room, while fire regulations require a window with a 600 mm base opening and a total area of not less than 0.45 m². The window must also have trickle vents.

Windows that meet these requirements are available in metal frame or uPVC, though metal frame windows must have a ‘thermal break’ (because of metal’s conductivity) to meet insulation requirements. Wood frame windows can meet requirements too, but they have to be of sufficient depth to accommodate a 24 mm double-glazed unit.

Doors must meet the same requirements as windows in terms of their U value. In addition to uPVC doors with double-glazed windows, wooden doors are also a good choice.

COMPLETION CERTIFICATE

Any project that requires a building notice will require a completion certificate, which is proof that the completed work comply with Building Regulations. Having a completion certificate does make a difference to the value added to your property by the garage conversion. Estate agents and prospective purchasers will value your completion certificate highly since things like an under-floor damp proof course can’t be proven without one.

Upon final inspection, be sure to submit to the building inspector the documentation proving that building regulations were met in the construction and installation of the parts he has not visually inspected. Once the building inspector is satisfied, the completion certificate should follow, often within 28 days.

If you are considering whether or not to convert your loft here are a few things to bear in mind.

HEAD HEIGHT

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.

Tip: Ask your architect to clearly illustrate how much headroom there will be across the floor in the finished space. (Some people can be disappointed by how much standing space they actually have, and this isn’t always easily conveyed on plans.)

PITCH ANGLE

The higher the angle of the roof pitch, the higher the central head height will be. If dormers are used or the roof is redesigned, the floor area, and potential for comfortable headroom, can be increased.

TYPE OF ROOF STRUCTURE

There are two main structures used in roof construction — 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 a structural engineer.

WATER TANK

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 can be 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.

CHECK YOUR LOFT FOR WITH OUR CHECKLIST ABOVE.

The main features to initially consider include height, access and obstacles e.g. water storage tank, chimney stacks, height and pitch.

APPOINT AN ARCHITECT/SURVEYOR TO DRAW UP YOUR PLANS

An architect or surveyor will confirm the loft’s suitability for conversion. It is also necessary to take into account whether the building will be adequate to take the added load of a conversion.

CLEAR AND PREP YOUR LOFT

With Building Control approval, work can be started by clearing the loft space.

CHECK YOUR WIRING

The electrical wiring and other services that are attached to joists and binders must be removed and rerouted. It provides a good opportunity to replace and improve the original wiring. This requirement is likely to mean that some services may not be available until the new wiring and any pipework can be replaced.

FIT NEW FLOOR JOISTS

If necessary, new floor joists can be fitted. The exact sizes will depend upon the spans, but might typically be 50mm x 220mm C24 or C16 timbers spaced at 400mm intervals. Where there is a window or door opening below this is bridged by doubled-up timber suspended between doubled-up joists. The intermediate joists are attached to the window bridge using joist hangers. New wiring and any required pipework can now be installed.

INSULATE FLOORS

The spaces between the joists are filled with insulation to a depth of 100mm.

LAY YOUR FLOORBOARDS

Following Building Control inspection, the joists can be covered with floorboards. Typically a tongue-and-groove chipboard sub floor is used as a base for your chosen flooring. Remember, if your loft is going to have a wet area such as a bathroom remember to use a water-resistant grade chipboard in this area.

REINFORCE RAFTERS

If specified by your structural engineer, rafter reinforcement can now take place so that the purlins, struts and collars can be safely removed. This will open up the area.

INSTALLATION OF DORMERS

Dormers can now be installed. This will involve opening up the roof, so dry weather is desirable to avoid the risk of water damage. The Building Control officer will inspect to ensure that the roof structure reinforcements are as specified.

INSTALLATION OF ROOFLIGHTS

If you need additional natural light into your converted loft, consider using roof lights. These are an effective way of letting in natural light.

FIT STAIRCASE

The point at which you fit your staircase will depend on a case by case basis but when in place it will give easier access to the loft area.

DORMERS TILED AND VENTS FITTED

The dormers are tiled and clad to fully weatherproof them.

WINDOWS FITTED IN DORMERS

The windows are then fitted in the dormer openings. Always double check site measurements accurately prior to ordering.

INSULATE ROOF

Insulation is placed between the rafters, with a 50mm air gap between the roofing felt and the insulation, to allow for ventilation Over this is further insulation giving a total of 100mm. In the roof space above there is 300mm of mineral wool insulation. Building Control inspection is required before the rafters and insulation are covered.


PARTITION WALLS

Internal partition walls are constructed These typically are constructed using 47mm x 100mm timber studs at 400mm centres, with additional noggins.

WALL PLATES AND FIRST FIX

Wall plates fitted between studs will provide a secure fitting to items like radiators; they can also be used to secure the boxes required for electric sockets and switches. This is an ideal time to do the first fix electrics and plumbing.

UPGRADE ELECTRICS

The new electrics must conform to Part ‘P’ of the Building Regulations and the 17th Edition Electrical Regulations. It may be necessary to fit a new consumer unit, or additional unit if the existing one has no extra capacity.

ACCESS PANEL FOR EAVES STORAGE

Access panels are a useful addition.

DRYLINING/ARCHITRAVES & SKIRTINGS

Plasterboard attached to the studs and rafters with drywall screws will provide the basis for the decorative plaster skim. Following this, the area is painted as required, and door architrave, skirting etc. fitted and painted.

BATHROOMS AND EXTRACT FANS

The shower room walls should be lined with a cement-based aquaboard, first ensuring that all the required wall plates are fitted, and that all the required services are accessible. The shower room also requires an extractor fan.

SECOND FIX, HEATING AND FINISHES

With wall and floor tiling complete, the shower room items can be positioned and fitted. Second fix electrics and plumbing is progressed. The radiators are fitted in place, and connected to the central heating system.

DECORATION.

Now you can decorate!