Need advice, tiling bathroom floor

[tbear]

Hi All

I need to tile a bathroom floor, about 2.6x2.1mtr. It's a 1930s semi with joists set at about 430mm apart and they look to be about 6x2 inch. The 2.1mtr is the size of the room along the length of the joists and the 2.6mtr is the size at of the room at 90deg to the joists if that makes sense.

The floorboards aren't too bad but rather than over boarding over them I was thinking of ripping them up and laying 18mm wbp direct to the joists.
As wbp comes in 2440x1220 I'm hoping I can just use maybe three to do the entire bathroom, one alone if laid at 90deg to the joists will almost cover the 2.6mtr bit with a bit of help from a noggin.

Does this sound feasible or am I going over the top with this?

 

[Richard C]

I always prefer to replace rather than overboard, ply thickness depends on joist size/span/spacing; 18mm is minimum. Can you measure the joist size? Can you advise the span of the joist rather than the room size of 2.1m? i.e. are the joists supported by a wall at each end of the 2.1m?

That room size is a bit unfortunate; I would normally lay the WBP ply along the length of the joists (2.1m) with the joint down the centre line of a joist rather than board across as you will need to fit noggins to fully support joints running across the joists; what’s the room layout, i.e. is there a bath along that 2.1m wall? Where is the door? A little sketch of proposed layout would be helpful.

Plan the joint locations carefully depending on layout away from main traffic areas if you can (under the bath if possible) but trim boards so you always span across at least 2 joists, avoid a narrow strip which will be less stable. Is there a joist run down each side of the room to support the ply edge?

 

[tbear]

Hi again Richard

Ive added a dogy drawing of the bathroom if this helps..

Untitled

• tbear
• 16 Jun 2010
• 1

Joists are 2x6 inch give or take a few mm and run across the room when entering the door.

The floor feels solid as a rock when jumping up and down, suspect they overdid things in the 30s...

 

[Richard C]

Joists in many older properties are usually 7 or even 8” deep but your 6” are probably due to the short span of 2.1m. If they were 7” or 8” joists, I would have no hesitation with 18mm WBP but you may do better to go up to 22mm to be on the safe side.

I would lay the boards with the joists with the joint along the centre line of a joist. You may get away with 2 boards but it really depends on the exact joist pitch; 1200 isn’t exactly divisible by 430 so you may be stuck with trimming the edge of the boards back to get over the centre of a joist which means you’re stuck with 3 sheets. You could go across the room with 2 boards but you’re going to have the cost of extra timber & all the work of fitting noggins right across the bathroom. You should be OK with the thin strip of ply in the corner by the towel rail with adequate support; it’s not going to subject to any real loading. Usual advise is to fit noggins on the two unsupported sides of the room but, TBH, if it’s not subject to load it isn’t going to be a problem. I would only bother with the bit immediately inside the door up to & under the sink & also where the W/C is fitted; the rest is only subject to minimal loading & will be fine. Make sure the edge of the board is fully supported across the door threshold; sister the joist if you have to. Watch where the bath feet are located & if not directly over a joist, fit noggins to provide decent support.

Fix with screws every 200mm & seal the back & edges of the WBP with an SBR sealer before you lay it. Do not prime the tile surface unless your adhesive manufacturer recommends it (not usual). Only use a quality trade flexible adhesive (cement powder) & grout not cheapo DIY crap.

 

[tbear]

Many thanks for taking the time to give this info, much appreciated.

I had thought of laying the board across the joists but as you say I'd need a lot of noggins to to support the edges, hard work.

Is this board easy to cut? If not I could get the timber yard to cut it.

Just one thing, how did you figure out where the towel rail is?

 

[Richard C]

Is this board easy to cut? If not I could get the timber yard to cut it.

If you’ve got a decent, carbide tipped circular saw, some clamps, a sturdy batten & a decent table to support it all on it's not too bad; if not get the yard to cut it if you can but make sure you get it right!

Just one thing, how did you figure out where the towel rail is?

Could say because I’m a smart a rse but it’s a pretty safe bet it’s gonna be where it says “radiator”

 

[tbear]

Almost down, one strip to fit. Cut it by hand as was a bit worried that my viscious circular saw might have pulled the layers apart; joists gap varys by about 5-6 mm so couldn't use the timber merchants cutter.

The joists are 7 inches not 6 so used 18mm wbp, found it surprisingly easy to cut with a new saw.