part garage conversion regs?

We part converted our garage by raising the floor using a timber wall plate and joist hangers. Chipboard floor fitted over. We also built a wooden stud partition to close off between the new room and whats left of the garage. The door from the house to the new room is fire rated with self closer.

This room was built as a playroom for the kids and purely designed so it can all be taken down and turned back into a garage if need be. No underfloor insulation was fitted.

Nothing else in the room was added or changed. Has any building regs been contravened??

It is unlikely that the work you have carried out complies with standards required by the Building Regulations (I'm specifically thinking of level of heat loss (insulation) but there may be other areas).

Ok.

The void under the new raised floor which is the old garage floor has been fitted with a damp proof membrane which covers the whole floor and rises up the walls untill it reaches the new floor level. The garage floor never had an air brick in it that allowed air to run under the whole house as the level is lower than the house floor (concrete)

the air can flow under the new floor easily.

The house is on the market but this room has not been listed on the particulars. Is this right?

You can only (legally) list rooms that have been built to Building Regulations so this is correct.

You may have required Planning Permission too.