Quite a few wood flooring manufacturers specify that bitumen paper should be used when nailing solid wood to floorboards on ground floor. I’ve always been wary of doing this as worried it might increase risk of rot developing in floorboards by stopping all moisture/vapour transfer to room above- any thoughts from others? Floor manufacturers obviously trying to avoid damage to their product but they’re not the ones responsible for any future problems with existing subfloor. Cheers Sent from my iPhone using Tapatalk
I would say if the subfloor is reading over 18%mc there is a problem which needs sorting before The paper goes down. Solid oak will cup at lower readings which the paper will stop Sent from my iPhone using Tapatalk
I haven’t fitted solid if mc is above 12-13%. Engineered I’ll go a bit higher, sometimes use timbertech which has a membrane but have used fibre boards plenty of times with no issues. Always a bit concerned about making the subfloor sweat if use a membrane/bitumen paper to overcome high moisture readings, but at same time I’m not happy ignoring manufacturer spec. Interestingly, I was told during a FITA course last year that bitumen paper should never be used for this reason Sent from my iPhone using Tapatalk
It’s a big what if? All I know is we nailed a wood floor down to battens last year. Customer didn’t want the paper put down for similar reason and 3 rows slightly cupped by the doorway where a small damp area was. I personally don’t think it would of cupped if we had used the paper. I think the vapour was in the air not in the batten as they were reading dry. I could see if the reading were really high maybe it would be trapped under and rot the battens, makes sense Sent from my iPhone using Tapatalk
So really if you find any damp readings they need to be sorted first. I would use it if there were slightly high readings in patches. As you say 12%-13% . Also to protect in seasonal changes. It can’t be used as a proper DPM but as a vapour barrier. I don’t think slightly high readings would lead to your subfloor rotting away. Sent from my iPhone using Tapatalk