Block floor (Bison?) Type flooring on top

[LeroyTheLC]

Have a block (been told it's a Bison style) floor in a bathroom and it's about 120mm below existing floor. Was going to use simple joist and 18mm marine ply on top then tile on top of it. Been told i should consider using celotek and screed on top but if i do that then i wouldn't trust the tioles not to crack on top of the celotek. Surely joist style flooring and marine ply would be a more sturdy base for floor tiles? would it be better to lay joist floor with celotek insulation between joists and ply on top of it? Any help gratefully received.

 

[Shytalkz]

With a screed over the insulation it will be fine.

 

[LeroyTheLC]

Thanks, just got call from friend who tells me last night he laid the 4 x 2 joists and 18mm marine ply ! He put a plastic membrane down before doing this. Is it ok like this or should i pull it up and go for the celotek/screed option before it's too late

 

[Shytalkz]

No, you can do it like that as well. Joists at max 400 centres though, or the ply will flex.

 

[LeroyTheLC]

Thanks for help i'll add extra noggins everywhere just in case. Do you know if there's any need for insulation ?

 

[Shytalkz]

Not really, unless it's a fairly recent building where you are replacing insulation that's been removed.

 

[LeroyTheLC]

Building is about 25 years old and this was an extension that was put up about 5 years ago and never completed. Many thanks for your help

 

[^woody^]

Never leave an unventilated void beneath a floor - that's a recipe for rot.

Use your joists, but infill completely with insulation - polystyrene or celotex/kingspan

 

[LeroyTheLC]

Thanks for that. I have now fixed door frame. Is it imperative ? Should i take up the floor and fill it? Would normal insulation suffice. I'll take your advice but if ever there was a leak, wouldn't it would get trapped between the joists and have nowehere to go... Just a thought

 

[Shytalkz]

It's not a ground floor woodster, so where's the cold to cause the moisture to cause the rot to come from? That's like saying every floor in every house must be filled with insulation twixt the joists....

 

[LeroyTheLC]

Thanks for help guys. Actually i forgot to say that this extension is on the ground floor. I've decided to remove newly fitted door frame, take up floor, cut and fit polystyrene blocks and stick into the holes twixt joists. At least this way all i'll be wasting is time and about 15 quid on a large sheet of polystyrene. Waddya think ? Good idea ?

 

[Shytalkz]

Sounds good to me.

 

[^woody^]

. Actually i forgot to say that this extension is on the ground floor.

LOL. I have the eye of Sauron

 

[Shytalkz]

Verily