How should I build my floor to accomodate future tiles?

[Rob1980]

Hi all, I know questions regarding wooden type floors has been asked many times on many forums, as Ive been reading.

However, I feel I need to ask the question specific to my own project to feel confident I'm doing the right thing.

I'll try to keep it short and to the point but hopefully provide enough info.

I'm building an extension on my 1950s bungalow, the new flooring is a concrete finish, with a height lower than that of the existing floor allowing for 100mm joists and 18mm floorboards.

So my basic question is how to build the floor in the bathroom..

The joists are long enough so that there will be no joins, noggins will be in place, they are c16 treated 4x2, (100x50) sat directly on the concrete, or at the most, raised slightly in places but remaining supported if the concrete floor is slightly out in that room anywhere (the other rooms have been pretty good so far).

I think you use the term deflection, am I right in thinking this would be close to, if not zero, as in no movement?

joists will be 400mm centres.

Should I put a single 18mm board onto the joists or use two layers to build up to 18mm?

What material should I use, please bare in mind, the cheaper the better, but of course I'm here asking to get a product that will suit tiles, so I understand its going to cost more than chipboard.


I think that covers it.


Thanks

Rob

 

[Time's Ran Out]

Although its a bathroom you haven't mentioned if you intend to tile this floor!
I personally don't think that 18mm is substantial enough for flooring and whatever board you use (plywood would be my choice) you need to add a further covering of a tile backer board if you are going that route.

 

[DHTiling]

Are you tiling just this bathroom floor. ?

 

[Protilers]

Cut the joists back if they are sitting on concrete........fill the bathroom floor with modified sand and cement (fibre reinforced) and tile on that.........just a thought....if I understood correctly?

 

[widler]

Why not just concrete it?

 

[Rob1980]

Yes, I plan to have the room floor tiled, that's why I'm here asking 🙂

(The clue is in the thread title lol)

18mm is more than adequate for flooring with 400mm centre joists surely? it complies with building regs, and my whole house has 18mm boards and is still standing 60 years on.

The joists are not in place, but I will not be screeding the floor, the joists are paid for, here, and something I can do myself to keep my costs down, I'm useless at any wet trades, and trying to save labour costs where I can.

I will be having this bathroom, another bathroom, and a kitchen tiled, but this question only applies to this room which is part of the extension, and the room with no floor at all yet (other than concrete which is not the finished floor as its roughly 120mm too low)

Many floors are tiled on wooden floors with joists, I have the luxury of ensuring this is flat, level and solid, I just need to know how to finish it to ensure tiling will be easier later on.

Thanks

 

[Rob1980]

Why not just concrete it?

I assume you mean screed, costs of materials, cost of labour, and the fact that I have the joists ready.

I wouldn't need to ask the question if it was a solid floor 🙂

 

[Rob1980]

Easiest way to think of this.

Forget it's downstairs, forget the concrete.

Imagine it's upstairs, I've ripped the floorboards up, and have the chance to support the joists making them solid, I want to tile the room, how should I cover the joists.

Thanks

 

[Wood's better]

Ok. You want to save money by not screeding.
The joists should be treated c16. If tiling on, it would be more solid to put them in at 300mm centres, but 400mm is ok.
18mm ply is, as you say, compliant with building regs at 400mm joist centres. However, this is minimum requirement and really only for carpet.
We have always used 22mm minimum. 25mm is better. My builders merchants stocks 22mm tongue and groove flooring plywood, which is good for a sub layer for tiling. 6mm Hardibacker glued and screwed over the top. It sounds like you are going to put the joists in more like battens. They must be packed and fixed down at close centres. 47x100mm timber can only span around 2 metres. All edges of plywood need to have noggins. I always glue the ply to the joists as well as the tongue and groove. I prefer the Spax flooring screw to fix, at 200mm centres, 60mm long. (Screwfix)

 

[DHTiling]

The clue might be in the title doh!!! ... but you didn't explain very well... IMO anyway..