Garage / garden room Insulated floor

[Moonshine]

I am looking at the option of a new build detached garage / garden room, as below;

 

When this is a garden room the garage door would be a proxy door, though may be converted to a garage at a later date.

 

As a garden room it will need power, heating and insulation. I am looking to build as circa 100mm timber stud, with timber cladding insulation in the cavity, plaster on the inside.

 

The main question i have is what to do with the foundations / slab. I was initially thinking of a concrete slab, with PIR laid down on top, electric UFH, and Ply / OSB + flooring above that.

 

However the main issue i can see is in future is that if it becomes a garage would this build up take weight of a car, particularly the UFH and PIR (i guess the UFH could be pulled up, but the PIR?

 

How would you approach this issue?

[Temp]

How about...

Concrete slab.

Two courses of engineering brick to raise the wood frame off slab.

DPC Between brick and frame.

Once water tight..

PIR infill 

UFH

OSB

 

Clad outside of frame in WBP ply to prevent racking then membrane, battens and cladding. The battens and cladding can extend down over the brick courses but stop 1" off the slab to keep them and out of any water that sits on the edge of the slab.

 

Not sure i would use electric UFH. Possibly fan heaters or an lpg heater?

 

Before you pour slab fit duct pipe for electric to come up in the wall. 

 

[Onoff]

20 minutes ago, Temp said:

How about...

Concrete slab.

Two courses of engineering brick to raise the wood frame off slab.

DPC Between brick and frame.

Once water tight..

PIR infill 

UFH

OSB

 

Clad outside of frame in WBP ply to prevent racking then membrane, battens and cladding. The battens and cladding can extend down over the brick courses but stop 1" off the slab to keep them and out of any water that sits on the edge of the slab.

 

Not sure i would use electric UFH. Possibly fan heaters or an lpg heater?

 

Before you pour slab fit duct pipe for electric to come up in the wall. 

 

 

So in this build up you've a 2 course high void under the wood frame? PIR goes between the floor joists?

[Onoff]

I was randomly doodling and came up with this work in progress for a future, super warm, garden room section. The only thing stopping me going ahead is time, money (£££££ I'd guess) and the probably need for pp that would likely be rejected anyway (AONB)! I've got loads of drawings like this, for numerous  projects that'll never happen..... ?

 

I was trying to see if a section was possible using stock heights of timber, pir, plaster board etc without cutting. 

 

Edited September 16, 2020 by Onoff

[Moonshine]

44 minutes ago, Onoff said:

I was randomly doodling and came up with this work in progress for a future, super warm, garden room section. The only thing stopping me going ahead is time, money (£££££ I'd guess) and the probably need for pp that would likely be rejected anyway (AONB)! I've got loads of drawings like this, for numerous  projects that'll never happen..... ?

 

I was trying to see if a section was possible using stock heights of timber, pir, plaster board etc without cutting. 

 

 

That is probably pretty close to what I am thinking, minus the insulated plaster board.

 

The question I have is if the pit and ufh would take the weight of a car in future?

[Conor]

I'd go for a concrete raft.100mm EPS100 (or more) with DPM, 100mm concrete + mesh above. Can be power floated for a smooth finish. Very simple solution and will easily take the weight of a car.

[Temp]

6 hours ago, Onoff said:

 

So in this build up you've a 2 course high void under the wood frame? PIR goes between the floor joists?

No. There is no floor frame.Just PIR and OSB resting on the slab as the floor.

 

If worried the PIR might compress you can lay joists same depth as the PIR but these would be between the brick not on top.

 

If not clear I Will try to make a diagram later but bit busy today.