Garden room insulation

[cjames1984]

Hi all,

I'm looking for some advice regarding converting an existing garden room. My house has an timber garden room which has mainly been used for storage since we moved in. Now I'm looking to make it more of a room and something that can be used all year round.
My first job is to insulate the base and install some flooring.
For reference it looks like it is currently sat on a concrete base and below this is a solid membrane.
I'm looking to build a frame inside around the existing floor with timbers across at 450, fill the gaps with 50 or 75mm PIR and then lay some OSB on top followed by some flooring (likely vinyl).
I have a handful or questions.
1. When I build the timber frame inside do a leave a small gap between the existing wall or can I fix to the existing wall (timbers are 40mm) for shrinkage and expansion?
2. Do I have to do the same with the OSB or can this butt up to the wall?
3. Do I have to install another memberane under the new frame and existing floor?
4. I currently have a double beveled circle saw, a hand circular saw, hand saw, impact driver, multiple spirit levels, laser level and hand tools is there anything else I will need?
I have attached a rough floor size and a picture of the room to give anyone a better idea of size and it's make up.

Many thanks

Craig

 

[jj4091]

You don't actually need to make a frame just lay down a floating floor with your T & G OSB boards on top of it. The only thing you may have to do is shorten the doors and raise the threshold. I used this https://www.wickes.co.uk/Jabfloor-70-Polystyrene-Insulation-Board---2400-x-600-x-25mm/p/287741 but you could choose from others https://www.google.com/search?q=pol...NjM0MzUxMjc3NjE=,pvt:hg,pvo:3&oshop=apv&pvs=0

 

[cjames1984]

Okay I wasn't aware of that I'll look into floating floors. Thank you.
The door frame is raised already so I'm hoping to get away with 50mm PIR and the OSB and still be below.

 

[noseall]

Okay I wasn't aware of that I'll look into floating floors. Thank you.
The door frame is raised already so I'm hoping to get away with 50mm PIR and the OSB and still be below.

Go for 50mm PIR with 18mm T&G (glued) flooring deck.

 

[cjames1984]

I've trying to get some info on floating floors and a lot of the reference material is about laying laminate. I was wondering if someone can clarify what is actually meant.
I understand that if I put timbers across at 450mm intervals this is where I am likely to get thermal bridging as this is where there is no insulation but if I have no timbers where will I fix the OSB boards to.
Thanks again for all the help

 

[jj4091]

You dont fix the boards they float on the polystyrene hence the name. You just need to glue them together as noseall said. That way they can expand across the lenth and width of the room. You need a small gap all around as you would with laminate flooring.

 

[cjames1984]

Okay that makes sense. Would all parts of the floor need to be slight shy of the wall or just the PIR and OSB and then take the vinyl/laminate to the wall?