sub-floor lip

[Guitardedleon]

starting to get somewhere with this bathroom Ive had planned.

so far I've:

Replaced door and lining.
removed all the old tiles
removed the old suite
removed the lino & tore up all the floorboards
re-plumbed
new electrics for heated & lighted mirror and IP65 spots I've had installed.
strengthened the joists and installed noggins

Ive also ply lined the floor , 25mm wbp primed on back and sides with SBR.
screwed to joists at 150mm centers.

however,along the one long edge is a lip of between nothing up to 2mm at the worst point.

this is a join going at 90 degrees to joist direction.

I plan on using a Ditra matt under the tiles.

is this lip ok?

thought it would go when screwed down, but can not fix it.

thanks in advance

 

[beanz]

2mm? That's the worst bit? How flat is the rest of the floor?

 

[Guitardedleon]

2mm? That's the worst bit? How flat is the rest of the floor?

2 or 3mm , yes mate.

rest of the floor is flat as was possible to get it.

room is only 8ft x 6ft so took two boards - has a total of 2 joins on the entire floor.
one long join (across the joists) and one parallel on the second board.

only the long joint is a problem, as mentioned has , at worst, a 3mm lip between boards.
hope this makes sense?

 

[Guitardedleon]

Just checked what was what exactly and the height difference between the two board edges is actually 4mm at the worst point and between 0-1mm most the way along
( highlighted inside of the green boxed area below )

Im due to be at the property at 3pm - so will take a couple photos of the actual floor too.

 

[beanz]

Have you considered SLC? As flat as you could get it, doesn't really say much.. Ditra won't make it any flatter, and I'd be worried about getting a proper bond in the area where you've got a 4mm drop. Personally, I'd latex it.

 

[Guitardedleon]

luckily I have two bags of slc sitting here!
as flat as i can get it is - level in all directions and a lip of less than 1mm. ( other than the area mentioned )

with the small gaps around the perimeter of the room, how would you prevent it from flowing down into the void between floor and ceiling?

also- any preperation tips?

 

[beanz]

You could attach some strip wood/battens around the perimeter.. Or silicone, if you were so inclined.. as for prep, just follow the instructions on the bag, and make sure it's suitable for Ply.

 

[Guitardedleon]

You could attach some strip wood/battens around the perimeter.. Or silicone, if you were so inclined.. as for prep, just follow the instructions on the bag, and make sure it's suitable for Ply.

just realised what the real issue is - the timber yard have given me two boards of slightly different thickness's, by a mill or two! (we have had nothing but trouble with their timber, since stopped using them! )

anyhow - some pics of floor:

 

[Stef]

Unscrew that sheet of ply & get a fivers worth of two pences & use them as shims!!

 

[Mr Tiler]

that doesn't look like 30mm centres to me! lol

 

[Stef]

that doesn't look like 30mm centres to me! lol

30mm centres?? You would use a box of 500 screws for one sheet!!

 

[Martyn Leeds]

You might be alright with 35mm centres

 

[Guitardedleon]

that doesn't look like 30mm centres to me! lol

sorry?

the ply is screwed at 150mm - ( apart from where pipes are below )

regarding shims - would that work good enough for tiles?
rather than the pennys ill just grab a bag of packers from the shop. i think its like £3 for mixed bag of 1mm-10mm packers

 

[Stef]

Was only having a laugh.
I would lift that sheet & put shims in & bring it up to the height of the other boards.
A lot cheaper than flinging slc at it.

 

[Guitardedleon]

Was only having a laugh.
I would lift that sheet & put shims in & bring it up to the height of the other boards.
A lot cheaper than flinging slc at it.

that's alright lol.

such a straightforward and obvious solution that I didnt even think of it! :lol:

is there an "acceptable" lip in subfloors? say 1mm between adjoining boards?

 

[Stef]

Depends on what size trowel?
I wouldn't bother about 1mm, tiled to a lot worse than that.

 

[Mr Tiler]

30mm centres?? You would use a box of 500 screws for one sheet!!

yeh is that not b.s? or is it the other b.s? lol

 

[Mr Tiler]

the floor I done recently fixed down ply at 20mm centres took me all bluddy day! think I used around 250-300 screws cant remember exact

 

[Stef]

the floor I done recently fixed down ply at 20mm centres took me all bluddy day! think I used around 250-300 screws cant remember exact

150mm centres is more than adequate.
At 30mm centres you would use 3240 screws,a bit much if my calculations are correct.

 

[beanz]

20mm or 200mm? 20mm centres would be a LOT more than 200 screws lol!

 

[Mr Tiler]

7.5m2 room overboarded and screws went down at 20cm/200mm centres drew the centres on boards and away I went had to wait ages cuz my crappy drill kept going flat.... I have been told in the past on this site that when boarding up 30mm is standard. I purchased 300 screws and there where about 15-20 left in the box

 

[Guitardedleon]

Depends on what size trowel?
I wouldn't bother about 1mm, tiled to a lot worse than that.

say for a pretty standard 300x300 ceramic floor tile - what trowel would you use (over ply+ditra)?
the ditra is only 50 quid so for the sake of say £70 and an hours work Id rather use it anyway.

regarding screws.. i used around 170 :lol:

 

[Stef]

say for a pretty standard 300x300 ceramic floor tile - what trowel would you use (over ply+ditra)?
the ditra is only 50 quid so for the sake of say £70 and an hours work Id rather use it anyway.

regarding screws.. i used around 170 :lol:

I think? Ditra goes down with a 4/6mm trowel,
I would just overboard with 6mm Hardie on top of the ply.
If its only ceramic I wouldn't bother with Ditra but if your getting it at a decent price then go for it, it won't do any harm.

 

[Guitardedleon]

sorry for yet more questions..

with hardiebacker do I need to tape/fill/anything where the ply joins, before spreading addy for the backer?

 

[Stef]

I never do, just stick the Hardie down, glued & screwed.