Garage Conversion Floor

[andyc007]

Hi
I'm going to be having a garage conversion done. I have enough height in the garage to do a subfloor with 100mm kingspan underneath. And 100mm insulation between the rafters for the ceiling. But doing a 4x2 subfloor will mean that the height of the floor will still be lower than my main house.
So knocking through from the dining room into the garage will result in a step down to the conversion.

Is this allowed?
If I HAVE to have the subfloor the same height as the house, I'm going to have to raise the height of the garage walls/ceiling, which is a shame asast year we had a brand new flat roof with rubber.

 

[Murdochcat]

If you are knocking through, then maybe ask your LABC ?

 

[andyc007]

I'm getting materials and plans in place first. So, if there is someone experienced, they could give me an answer, yes?

 

[thomp1983]

How much lower are you talking?

I did a floating floor for mine with 120mm celotex on the original garage concrete then 22mm t+g chipboard flooring on top.

Basically just use thicker celotex or frame covering to make up the difference

 

[andyc007]

I think if I have to raise it to the same level I won't have the head height so the ceiling will have to be raised. Bummer.

 

[thomp1983]

What height are you calculating you'll have?

The above picture is mine and we ended up with 220cm floor to ceiling and even with the stupid light the wife chose that hangs down 40cm I can still comfortably walk around, we'll be having a bed in there so the heights not so bad for us.

 

[andyc007]

I reckon of we raise the floor, and then insulate under the rafters to meet regs, I'll have 2.1m approx
No one is over 6ft in our house......

 

[thomp1983]

I'm 5ft 10, I think you'd be ok at 210cm, it will feel a bit low but from a practical point of view it will be fine to walk around in.

I suppose what you are going to use the new room for may have some bearing.

 

[andyc007]

It's an office (study) / guest bed for occasional visitors.

 

[^woody^]

You can have a stepped floor. The question is whether you want one.

Likewise, you can have a low ceiling, and the same question as to whether you want one, will apply.

 

[Ivor Windybottom]

The room I'm sitting in now is a flat roofed extension. I lowered the ceiling to add more insulation above it. It's 2.25m floor to ceiling and is bearable but definitely looks low. I'm 6'1" and can press my flat palm against the ceiling. I would have thought that 2.1m would start to look a bit extreme.

Just choice I guess, step vs height. You'll get almost zero insulation benefit from the thicker insulation and it will cost more. Lots of houses have split levels, some design them in just to make it more interesting.

 

[Ivor Windybottom]

Do you have a flat or pitched roof? Moving the ceiling joists up may be an option.

 

[andyc007]

I have a flat roof. We just had a new rubber roof done last year, so reluctant to mess with it really.

 

[Ivor Windybottom]

Oh, definitely not then. I was meaning just if pitched.

 

[^woody^]

What ever you do, you should ensure that it looks contrived and meant to be - not an accident or a make-do. So if say, a step is required, form a step and don't try and have a bit of a step. But even so, it may still be undesirable. And can make the additional area always looked tacked-on.

For the ceiling you really should have a layer of insulation below the joists as well as between, to avoid pattern staining of the joist line.

There are ways to decorate to minimise the appearance of low ceilings, but not always, and window and door heads are always a give-away

It really is not too much work to jack a flat roof up without disturbing the cover. And in context, you'll be looking at the room for years, so a day or two's work and a few hundred £ will be worth it