outside insulation Information, help, tips and advice on cavity walls, ceilings and lofts etc....

[stmull]

Hi.

Can anyone help?

I have planned to build an 8mtr x 5mtr garden room that has a single breeze block wall as this will be cheaper than wooden frame. It will also have a warm flat roof.

If I use block for the wall , I will need to insulate the outside as space inside is fully utilized.

What would the advice be to achieve this ? I will also be cladding with Cedar.

would I need to include a vapour barrier for the inside of the wall with plaster fixed to wooden batons? leaving a 50mm gap for services

Also where would the DPM membrane go on the outside wall insulation.

your advice would be greatly appreciated.

Thanks

Sean

[welsh brickie]

If it was me I would paint bitumin on the outer wall as its very effective and cheap,Fix 50mm x 50mm treated battens on the wall and use 50mm drytherm insulation, then fix your cedar to the battens.

[welsh brickie]

sorry forgot to add if you fully paint the outside with bitumin that should keep it watertight.
With regards to the inside you could dryline the walls with plasterboard ,but make sure you leave a 50mm gap from the floor to stop moisture rising up.You can hide the gap by gripfilling the skirting in place

[stmull]

Thanks for the advice.

Would i need a breathable membrame or DPM over the batons/insulation before adding the cedar?

Thanks

[welsh brickie]

No the bitumin is the dpm,the breathable membrane is no required

[Perry525]

A garden room will not of itself create any water vapour.
Water vapour/condensation will only become a problem, it you boil kettles or take baths in the room. Other than that, the source will be the breath and sweat of the people using the room. Unless you pack the room with people, the water vapour will merely sink into the walls and disappear into the sky.

However, if you place a waterproof insulation or coating on the outside, then the water vapour will be trapped inside the wall, this will do no harm except to make the wall cold.

The way to proceed is to place a waterproof membrane on the inside of the room, to keep the very small amount of water vapour in the room and to encourage it to disappear by opening a window or door.

The insulation can then be placed on the outside of the walls.