I'm looking to extend the attached garage on my bungalow. Currently there is no internal access - just access via the garage door. The garage has a flat roof and the house has a pitched roof - the adjoining side of which drains onto the garage roof.
I wanted to extend the garage further out and use part of the existing garage space for a kitchen and utility. There would be access from the utility space to the garage.
I'm concerned about what building regs would be required - particularly in relation to compartmentation and the requirement for the fire walls to project 335mm out of and above the rooflines :shock:
Would this apply to such an extension to an existing bungalow?
Any other things I should be aware of that might put the kybosh on the whole idea?
I have tried to post a couple of images but the HTML option isn't available?
The 385mm projection to roofs is usually a condition in and around London (although not really needed). It certainly would not be required between rooms in the same dwelling, more for compartmentation between different dwelling houses.
Building Regulations would require the usual items for the extension(extended part of garage) Foundations, oversite, DPC, Drainage etc.
The existing garage would need to be 'upgraded'. If you have a standard 100mm wall you will need to form an insulated cavity wall by either building another wall or by forming a studwork wall. The floor will need to be raised and insulated and the existing roof will also need to be insulated. The wall from the utility to the garage will need to be constructed as a compartment wall with 30 minutes fire resistance from both sides. The door in this wall will need to be a self closing 30 minute fire door and you will need to form a 100mm step down (which will be formed naturally from the raised floor)
The existing dividing wall between the living room and garage is a 250mm block cavity wall. The existing garage external walls are solid 9 inch brick.
As you can see the kitchen - utility & living room would all adjoin the garage. So all of the adjoining walls would need to be fire rated both sides? What is the commonly used method to achieve this fire rating requirement? I guess the existing cavity wall would already comply? I assume the ceiling of the garage would need to comply in the same manner?
I propose to replace the existing garage flat roof and construct a new flat roof covering the newly formed spaces with a warm deck structure incorporating 100mm insulation. Therefore any heat loss through the heated room walls would hopefully warm the unheated garage a little.
The external 9" walls will require a breathable membrane (to stop any damp that might penetrate through, then 2x1 battens with 65-75mm of thermal board Celotex, Kingspan etc and then plasterboard and skim.
The internal cavity wall dividing the habitable rooms will not require any work (can leave brick exposed if you wanted to). A cavity brick wall will achieve 30 minutes seperation without treatment.
The garage ceiling would need to be lined with 1/2" fireline board and skimmed. The insulation to the roof would need to be around 125-135mm of Celotex, kingspan etc.
Consult your local Building Control (over the phone) and see if they are happy with the above - they should be.
Whilst I have a 30 minute fire door beteween my attached garage and utility room (and 10mm step) I notice that there is a large gap on either side of the eaves. My house was constructed in 1990. Is this legal regarding Building regs as it kind of defeats the object regarding my firedoor. Anyway I have noticed that mice seem to be using this to access my roof space. Advice would be appreciated since I might possibly be able to get my builder to eliminate the mice problem for free.