Converting a garage, but keeping the garage door

[rjds319]

I'm converting my garage to a habitable office-type room, but I wanted to retain my garage door, so I still have the large doorway, and so it's back-convertible in the future.

I'm planning on painting the existing floor with liquid damp proofing, then adding electric underfloor heating with a floating floor on top. I'm just unsure about how to finish the edge where the floor meets the existing garage door. I'm getting a new wooden door and insulating it, but it's a standard size so the new floor would be higher than the bottom of the door. My thought was just to put a piece of timber across the front (image below), would that be acceptable? The driveway slopes so no risk of flooding.

 

[Tigercubrider]

as shown, any damp or rain will enter and sit above the DPM.
Is this door intended to work?
The DPM needs to go upwards and allow any insulation or heating to sit in an envelope of proofing.

 

[JohnD]

I would be strongly tempted to run a brickwork plinth (probably only needs to be one brick high) all round the garage, including in front of the door, not touching the walls, to form a tray that you can line with DPM. any water from the walls or under the door will not affect it, and you can lay your new floor inside the tray. If you are lining and insulating the walls, you can stand the studwork on the dpm on the bricks.