Hi everyone, I’m in the process of planning a garage conversion on our property, just for clarification its a 4 bed detached home, all exterior walls including garage are cavity walls.

Currently our garage flooring sits around 180mm below that of the floor in the hall which is adjacent to it, the doorway into the garage will be entering in from this hallway and I would prefer if the garage floor was level with this hallway floor (though from reading building reg’s, it doesn’t appear to matter if there is a step down in to the garage)

Is there a way of raising the floor to this level with possibly introducing a 2″x 6″ (38mm x 140mm) framework sitting atop a solid or liquid damp proof membrane straight on top of the existing concrete garage floor, with kingspan or similar insulation between the beams, then topping this framework with a solid 30mm wooden floor

Does this sound acceptable? the wording on the planning portal website is whats led me to this question as on one hand it makes it sound like the above is acceptable, and on the other hand there is a part where it mentions there must be a 150mm void between the floor and the beams.

any help on this mater would be greatly appreciated

p.s this is my first post, please be gentle with me!!

  • Mark Brinkley


    The regulation requiring an attached garage floor to be lower than rest of the house is there to stop flammable liquids spilling over into the house – i.e. it’s a fire risk. If you are converting a garage to living space then the reg will no longer apply.

    Essentially you are free to build up the existing floor however you wish. Note however that it may not have a damp proof membrane in place (I think you’ve already spotted that) and it won’t have any insulation, which will tend to make it cold.

  • Tony Edwards

    Hi Mark, yes it is going to be used as a living space, we will be insulating in-between the new wood floor framework, the wording on the planning portal is a bit confusing!!

    I just want to have everything ready so when the building inspector turns up I can just list off all the conversion points and satisfy them in one hit.

    thank you for your response!


  • Rachel Haynes

    Hi Tony,

    It is usually advised that with a suspended timber floor construction that you have a ventilated cavity below the level of the joists of at least 150mm to reduce the risk of the timbers having contact with moisture and ensuring there is no build-up of condensation. By placing the timber joists directly on a damp proof membrane you are relying completely on the membrane being completely sealed and do run a risk with condensation below the insulation due to lack of ventilation. I don

  • Olivia Cappuccini

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