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Discuss Suspended Timber Floor Tile Prep in the Tiling Forum | Tile Advice area at TilersForums.com

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You can fix mechanical expansion joint to bridge where the 2 floors meet,& by cutting up to the joint continue it with the off cut & it still gives the impression that the floor runs through
 

Deyna

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Thanks guys, this stuff is good.

I've got spare timber, so I will go ahead and double up the spans showing deflection and re-test. I think this will solve any lingering deflection problems and shouldnt take a great deal of my time.

I'll look into Blanke Permat for this subfloor. The extra expense might be worth it (12m2), but Ditra would be more suitable for the adjacent room with screen/WUFH and more cost effective. Both add the same height so would work.
 

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  • #44
I live in Warwick if you would like to pm me. I can come have a look.
Cheers buddy, I'll be working on it this weekend so will report back after bolting some more 4x2's together. A second opinion would be much welcomed.

I should have gone gone 6x2 really and just cut back at the ends. Wouldn't have got anything bigger than that in though.
 

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I've given it a bit more testing, and I've come to the conclusion that bolting more timber together will not reduce vertical movement to an acceptable level to be considered for tiling. However given the sleepers are 2 courses, I'm going to basically add another 2 walls mid span either side so the max clear span is 1m. I've got aload of spare blue engineering bricks here from the previous owners. A quick test of deflection over that span with some offcuts shows it will not move.
 

acaciaguy

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I agree. The thing with bolting them together is that you aren’t increasing the x4 part. They do need support underneath. You are doing the right thing.
 

Deyna

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I agree. The thing with bolting them together is that you aren’t increasing the x4 part. They do need support underneath. You are doing the right thing.
Ye, the strenght comes from the depth not the width. I can leave the existing frame "as is" then (the extra support for board joins isnt a bad thing plus it'll still be where foot traffic is).

Realistically its about 50 bricks and I'll just have to make do with workaround around the existing frame. I will feel a helluva lot more comfortable with it then!
 

Deyna

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  • #49
Ye for sure! I'll do the first two and consider rebuilding the others if thats the case to take up some of the slack underneath (upto 20mm shims in places). Feels like an extra weekend on it will be worth it in the long run.
 
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If you've got 50 bricks you could support most of your beams shown in your orginal pictures ,this would hopefully stop any bounce what so ever
 

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If you've got 50 bricks you could support most of your beams shown in your orginal pictures ,this would hopefully stop any bounce what so ever
Thats the plan! Max span will about around 1m then. Just need to decide on appropriate underlayment but I think Ditra would be OK to keep the height down to a minimum.
 

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Morning @Andy Rhodes !

I'm a little tight on height yes! The new subfloor is flush with the adjacent screed and the wood floor. Both substrates need a decoupling layer so Ditra would be the best bet from herein.

I built a couple more sleepers over the weekend, went back around and packed out with slate and plastic shims for small adjustments. Blocked in the frame at opposite corners. The max clear span now is approx 800m at any point. Ply joints have a small expansion gap.

Probably give it a more rigorous test this evening as I left the mortar to go off but on first showing it was much improved the missus did a bit of jumping mid span on a few joists and the laser was moving at most 1mm and nothing at all if you're walking around normally.

The length of the tiles are 1200mm, so when you run them perpendicular to the joists you're actually spreading the load along 4 lengths so I'm not worried about any interstitial deflection between them due to the ply thickness.
 

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I'm still torn on Ditra or 6mm hardie though. I can accept the extra height to strengthen the subfloor a little more for belt and braces

Would someone be able to recommend me suitable adhesive/grout for such large format tiles. Something thats got a bit of "flex" in it.
 

pjc

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A little trick I found is cut strips of 3/4 ply the size of the joists and glue and screw to side of joists, it can make quite a bit of difference sometimes.
 

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  • #61
To be honest I've spent the last couple of nights poking and prodding and even with the extra walls its just not good enough...

View media item 16018
Even with overboarding again I don't think this can be eliminated or at least reduced to an acceptable level.
 

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  • #62
Back again...the things you do for love :)

I did a slightly more visual test by running some building line over a specific joist and put a 3mm shim for reference. The building line was 2mm at most.

So while the the movement looks bad to me (I really have no point of reference though), the visible deflection cannot be more than 1.5mm as at no point does the building line rise above the shim but you can see clear air underneath.

So if the allowable deflection over a 3ft span is 2.5mm (36/360) then the L value is more like L/720 observed.

If someone were tiling a standard bathroom i.e. 8x2 joists, 10ft span and 16"OC then the allowable deflection is 120/360 which is about 8mm. I cannot imagine doing the same jump test on this setup would yield zero movement.

I'm still feel like some extra noggins or doubling up with the left over timber would provide some more assurances though I just dont feel like it would further reduce what I'm observing.

View media item 16019
 

pjc

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Put a full glass of water till its convex. Then jump on the floor. if it OK the floor will be dry. That's the old way.
 

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I did however spill my beer last night after foolishly putting it on the floor. Didnt even have a sip :/
 
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What you need to ask yourself Denya is can you live with the 1.5 mm deflection, because if you can you answered your question you asked us all & all this has been possible because of all the good information you have provided us with
 

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  • #68
@Andy Rhodes Thanks fella, you guys have helped massively. Like I said its hard not having a point of reference for what is acceptable. I feel more confident given the additional steps I took on everyones advice and I am happy to take this risk now. The overboarding with cement board removed any flex in the ply as well.
 

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So heres my progress...

Had to use the levelling clips due to slight bend in the tiles would not have managed to lay without lippage so something to be mindful of when evaluating plank tiles next time.

Unfortunately I think they are expensive junk (the clips) but in this case a necessary evil to get a good finish. I found that probably 80% of them snapped incorrectly so I'm using my multitool with to grind them down to where they should be. Obviously this is due excess adhesive squeezing up around the clip when putting the tile in place but it seems difficult to find a balance without leaving voids around the clip areas. Didnt feel like I had too much addy though so I will need to find a solution for the extension as I wont have the patience to make good such a large area!

Again, thanks guys for the help. Had some good fortune with end of tile landing right on the pipes so saved me taking the rad off :)

WhatsApp Image 2019-04-14 at 12.05.06.jpeg
 

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No! I'll admit it looks like it doesnt it. 6mm Cement board.

Unfortunately it was a case of local availability. If there is a better product please let me know I would rather not use these again.
 

Tom Astley

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No! I'll admit it looks like it doesnt it. 6mm Cement board.

Unfortunately it was a case of local availability. If there is a better product please let me know I would rather not use these again.
Just buy them from ebay..... you have used the lash clip set that have curved bases.
 

Deyna

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Ye I know what I bought. Ebay has a lot of junk so is there a better design I should be looking for? Anything similar to this will just have the same problems. Ideally a system that is re-usable given the area I need to work on...
 

Tom Astley

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Ye I know what I bought. Ebay has a lot of junk so is there a better design I should be looking for? Anything similar to this will just have the same problems. Ideally a system that is re-usable given the area I need to work on...
you can only reuse the wedges......
 

Deyna

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Unfortunately I wont trust those wedge style ones again. Long evening ahead :D
 

Deyna

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Fair enough...if you care to expand I would be more than happy to learn!

Too much addy? Bed too small (10mm + back buttered)? Laying the tile incorrectly? Not kicking them straight?

Why would a similar design work any better?
 

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