Conversion of Garage into Living Accommodation.

This type of conversion is becoming more popular. This is due to space becoming more a premium and coupled with the fact that an average car will not fit into the average attached garage.

Owners are often shocked by the price of the work when embarking upon this alteration. Therefore I have produced an explanation of the Building Regulations that apply and how they may be overcome.

Before starting any work it is essential you contact Development Control to establish whether Planning Permission is necessary. Some more recent consents have conditions that only allow the garage to be used as a garage. Under these circumstances Planning Permission is required to remove the condition.

General Building
Infill panel of brickwork that replaces the existing garage door should be built off;

1) Existing foundation subject to inspection
2) New foundation subject to inspection
3) Designed ground beams

Structural openings that open the converted garage to the hall will change the means of escape in case of fire. Seek advise before carrying out this type of work.

Do not remove the garage stiffening piers unless a new structural masonry or timber frame leaf is being provided.

Ensure that any openings are structurally designed and the calculations sent to Building Control as soon as available.

Internal Fire Spread Requirements
If the existing garage is only to be reduced in size instead of a complete conversion, the fire separation between the house and the garage must be maintained. Therefore any new wall must achieve a fire resistance of 30 minutes and any door must be a FD30’s with a self closing device.

All ground floor beams will require 30 minutes fire resistance.

Weather Resistance
Unless you know there is a damp proof membrane within the existing floor a new dpm will be required.

If your existing garage wall is only 1/2brick with stiffening piers some method of preventing the passage of damp into the new room will be required.

Roof Ventilation and Condensation Control
Where a roof was previously un-insulated there was no need for any ventilation. However, once insulation is provided within the roof, ventilation must be provided.

Roofs must have cross ventilation on opposite sides to achieve the equivalent of 10,000mm per meter of roof and flat and skeiling roofs must provide 25,000mm2 per meter.

If you elect to provide a “warm deck roof”, ventilation will not be required. However, details must be provided of the system you choose, so that its suitability can be checked before installation.

This issue is creating some problems at the moment, if you have any questions on this topic speak to the surveyor on his first visit.

Downlighters are not permitted within cold deck flat roofs unless careful detailing is carried out. This will only work if the void above the insulation is larger than 150mm. However, if a warm deck roof is provided downlighters do not normally present a problem.

Protection Against Sound Between and Within the Dwelling House
Where the converted garage is attached to another building, sound insulation between the converted room and the attached building is required.

The amount of work required to achieve the required standard will depend upon the existing construction. Approved Document E gives guidance on the various types of construction for cavity and solid walls exceeding 225mm in thickness. Should the separating wall be 100mm brick or block specialist advice must be sought.

Ensure that any partitions created that do not contain doors are insulated with a suitable sound absorbing quilt in accordance with Approved Document E.

Conservation of Fuel and Power
The external elements of the converted space must have their insulation upgraded to achieve the following values;

1) New and existing walls 0.35W/m2/K
2) Floor 0.20W/m2/K
3) Roof 0.16W/m2/K and 0.2W/m2/K for pitched and flat roofs respectively. (Skeilings to achieve 0.2W/m2/K)

Windows and Ventilation
Windows are subject to a number of regulations but typically they include;

1) Windows and doors require U values of 1.6 and 1.8W/m2/K respectively
2) Should be set back in reveal approximately 40mm over an insulated cavity closer
3) Require ventilation opening to achieve 1/20th of the floor area
4) Require 8000mm2 background ventilation at least 1.75m above floor level.
5) If the new room is only accessible from another room, the window will be required for alternative means of escape. This must be 450mm deep or high with an area of 0.33m2. Typically 750 x 450 will comply, this must be a max of 1.1m above floor level. This casement must use fire egress and not easy clean hinges.
6) Windowless accommodation, wet rooms and kitchens must have mechanical ventilation. If the fan is being ducted in excess of 1.5m, a check must be carried out to ensure that the reduction of capacity does not result in the fan not achieving the minimum standard.

The following regulations apply to the services

1) Efficient lighting to be used in the new room
2) Thermostatic radiator valves to be used on new radiators
3) Ensure that any proposed drainage is either agreed on site with the Building Control Surveyor or sent into the Council for approval. Tread carefully about cutting through the floor for below ground drainage, as most of the floor slabs in this area are suspended. Any cutting could destroy the structural integrity and therefore must be carefully considered. If in any doubt obtain the services of a Structural Engineer.
4) Any services that breach a fire compartment wall between the house and any remaining garage must achieve 30 minutes fire resistance. Any mechanical ventilation ducting or above ground drainage must be encased in 30 minute fire resisting construction.

Certain work contained within the Building Regulations can be self certified. A copy of these certificates must be provided for our records before we can issue a completion certificate. Typically these include;

1) New or repositioned boiler
2) New or repositioned un-vented hot water installation.
3) New or alteration of the electrical installation.
4) New window where installed by a Fensa Registered Contractor.

For a full list of works that can be self certified and the bodies responsible for persons carrying out this type of work refer to schedule 2A of the Building Regulations 2000.

Author: Les Ryder

Categories: Building Control, Uncategorized

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