Hi,

please answer as many points as you can :-)

first, the history.

Our house is 1930's

When we bought it, it had a (partially rotten) sun lounge with a balcony
above where the wooden rails had rotted and been sawn off then the whole
thing felted over (so not much use as a balcony).

As far as we can tell, originally there was a tiled patio area on which the
sun lounge was built.
At least, the windows, doors and walls all seem external walls, including
the underfloor ventilation grilles.

The tile floor is at 'ground' level not 'floor level' and there is a step
down through the doors from the lounge.
The tile floor also has a definite slope - 1" in 8' - which suggests that it
was originally outside and designed to drain away from the house.

When we could afford it, we had the sun lounge and balcony replaced with a
similar but slightly large and more modern design.

We didn't, however, replace the floor (budget).

The original tiles have no damp proofing under them - when it is very wet
you can see damp rising through them.

The sun room, though nice, is a little under-used and we would like to
lighten and brighten it.
We would also like to have a level floor, with the possibility of real wood
or photocopied wood flooring.

Dimensions (at floor level):

8' 4.5" high (plus 1" downslope)
8' 3.5" wide (plus a bit more where the outside doors are
20' 6" long
floor has 1" drop over 8'
4" up to the base of the door step from the lounge
6.75" up to the top of the door step from the lounge.
Low brick walls to the outside with double glazed units above, apart from
The outside doors - fitted in a space 10" deep (i.e. no brick walls) and 7'
2" across.

I don't really want to level the floor out with a flooring compound.
I would like to install a level floor, preferably with an air space
underneath to allow the tiles to breathe and air to get to the under floor
vents.
This leave the option to take it all out in the future.

My original thought was to just make up flooring grade chipboard with wooden
batten supports underneath, shaped to the slope in the floor, laid on
plastic or similar to provide a damp barrier.
Basically a 'drop in' floor which could have a floating floor above.

However the dimensions (8' 3.5") are just too long for a single sheet of
flooring.

I am considering strap hangers on both brick walls but that leaves the
problem of the gap by the door.
Presumably I could lay a beam across the gap. and fit strap hangers to that.
I would need a step down to the outside anyway.
One question is do I continue the wall line with a beam, then have the step
inside the doors, or take the floor line right to the outside doors (which
would then close onto the beam and the base would be below floor level).
If I lay a beam directly on the floor, then I will have to put some kind of
damp proof membrane between this and the tile floor.
Is laying it on the felt type damp proof roll you use for brick walls
sufficient?

I also think I should put in floor vents directly above each underfloor vent
for the main house.

It might be good to take the floor level up to that of the lounge, thus
making the sun lounge seem more directly connected to the rest of the house.

Because of the (lack of) depth I don't think I can design a standard floor -
the thickest beams I could probably get in would be 2*4 - so I would have to
have a lot of shallower beams/joists instead.

As I am modifying an existing room would I need building regs. at all?
ISTR they are only needed for new build or changing the numbers of rooms
etc.

TIA
Dave R

P.S. It may all become horribly expensive - in which case does anyone have
an idea about how much it would cost to put a damp proof course and
levelling compound over an existing tile floor?
And also how much depth is required for this?

--

David W.E. Roberts wrote:
I also think I should put in floor vents directly above each underfloor vent
for the main house.

I would suggest using pipes to duct the main house vents right out to
the exterior with new air bricks in the sun lounge wall. The new floor
void you are creating will also require ventilation.

As I am modifying an existing room would I need building regs. at all?
ISTR they are only needed for new build or changing the numbers of rooms
etc.

I think the work is covered by B Regs - you are creating a new suspended
wooden floor and so it should be compliant. You can't (I think) get away
with the 'not worse than existing' because there isn't an existing
suspended wooden floor. Whether you choose to get the council involved
is up to you.

Owain