Shed floor - rockwool

[subhuman]

Currently building a shed/cabin, won't be insulating the walls for a while, but now is the time to sort the floor out.

I have several rolls of 200mm rockwool lying around - I know it isn't as good as polystyrene or celotex/kingspan, but can I put this to use?

The floor joists are 6x2, so a fair bit of depth. Frame is elevated around 2-4 inch on blocks.

Would this be a case of just building plywood 'trays' on the bottom of the frame to stop the rockwool falling through and keep rodents etc out? Do I need to use any sort of breathable membrane, polythene or anything under the finished floor?

Cheers

 

[subhuman]

Re-reading my own post, I guess what I'm getting at it this - the rockwool needs to stay dry and need to protect from nesting animals

 

[ntb]

I think this is workable in principle but the devil is in the details. Ventilation is the issue - if you box in with plywood at the bottom you lose this. If I'm visualising your design properly I would be inclined to hold the insulation in with a membrane at the bottom and try and keep critters out with some sort of mesh around the frame the the joists sit on.

 

[subhuman]

Cheers, I'm with you.

Although - presumably there is no ventilation when using polystyrene or celotex, right?

 

[foxhole]

No point insulating the floor of a shed unless it's in contact with the ground, yours is raised?

 

[ntb]

Cheers, I'm with you.

Although - presumably there is no ventilation when using polystyrene or celotex, right?

You wouldn't be boxing it in with plywood though. If you did, you would still leave an air gap.

 

[subhuman]

I'm thoroughly confused now

Do I need to insulate or not as my shed is raised off the ground? I appreciate heat rises so any heating in the shed would not escape through the floor as such, but presumably cold wind would be forced up through the floor from underneath?

...and in discussing this with my father, he tells me he has a couple sheets of 100mm polystyrene I can have. Does this mean I can just wedge them in between the joists and be done with it ? (I appreciate that the wood won't be insulated and will provide a path for thermal transfer)

 

[ntb]

My shed (pfefab) has insulated walls and roof that I retro fitted. The floor isn't insulated and I get cold feet in the winter. If I built from scratch I would insulate the floor too. I think you're doing the right thing assuming you want to use it in winter.