Urgent building advice!

[Don82]

Will begin renovating/expanding the house next weekend and just need to check a few questions before purchasing materials.

1. The extension will stand on pillars and be built as a deck with joists. It will be insulated with 19.5 cm. The question is whether to put treated planks under the joists and lay in an asphalt board before insulation or if it should just be insulation and be secured without enclosing the insulation?

2. I was thinking of skipping the roof boarding and associated tar paper and instead using oil-hardened masonite to replace this. Does that work?

Grateful for answers!

 

[Mats]

1. Skip the treated boards and use regular ones. The entire structure should have air underneath it anyway, so no pressure-treated wood is needed. Otherwise, it works fine to go with asfa plus insulation in the compartments.

2. Yes, works well especially if you have a light roof like metal above.

 

[Don82]

Thanks for the quick responses! Yep, it will be a regular metal roof, so it will be easier with large sheets to just lay down.

 

[Erik E]

Oil-hardened masonite also works when you are going to have a concrete roof!!??!! Just make sure the air gaps, etc. are correct.

 

[Don82]

A silly question perhaps, but why isn't plastic needed on the floor under the chipboard?