Dingdongler

I know it's Christmas morning but we're having Christmas supper this year rather than lunch as some family members are working during the day.

Anyway, as soon as the holidays are over I'm having a large area tiled. To complicate matters part of the room has a sub floor that is suspended timber and part is concrete.

I've spent quite some time ensuring the timber section is rigid, ie joists have been replaced or doubled up, lots of noggins inserted, brick or wood supports inserted. It's then been covered with 22mm WBP ply and then 6mm marmox board which has been placed such as to cross cover any joints in ply.

Anyhoo, I keep seeing stuff on the web that says that any run of more than 5m (especially if you have underfloor heating) should have an expansion gap rather than grout. Some people advocate just using a flexible silicone others use preformed profiles.

Could anybody (who knows what they are talking about and hasn't been on the sherry already) shed some light on this? Should I have an expansion gap after 5m?

Thanks and seasons greetings

stevebt

iTrader: (8)

It can't hurt but why not just ask the tiler that is doing it? There are plenty of big shops and toilets that have tiled floors and no expansion joints so

wrx300scooby

Mix PVA into your grout mix, it makes it much more flexible.

andy97

iTrader: (1)

It is recommended to have an expansion joint especially with a difference in bases. My tiler used a colour match silicon.

ALi-B

iTrader: (1)

Well we've just had that and no expansion joint between the old build (suspended with underfloor heated) and new concrete (underfloor heated too).

This is the first thing I questioned with the builder at the time as it was going to be awkward getting underfloor heating and a identical level floor throughout, and he said it'll all be OK.

Well, one tile has cracked in the divide between teh old and new. Now this could be bad luck or the plumber running the underfloor at 80degree and 36+degree floor temp (yes, he's a idiot), or teh screed/building settling.

The builder wants the broken tile replaced ASAP, but the tiler reckon to wait a few months and see if others crack. I'm siding with the tiler at the mo.

Eitherway I'm not too pleased and I do think an expansion joint probably would have allowed for some movement. Problem is I don't know what they did with the subfloor or screed as I was away, so have no idea of whats going on under there. Really p*ssed off with myself about this, because if I was there my OCD would have spotted anything untoward and I'd have questioned it at the time it was built, rather than now when its all horse stable bolted.

Now I'm not got anything against the builder as he does have good intentions. But he is very trusting of the people he employs on issues that are not his expertise, he takes on their opinions a bit too readily, which is fine as long as that person is right. The problem is is when they talk out of their ****, the plumber and polyplumb rep has since proven to be just that.....they said I would be "mad" (their own words) that I should have additional radiators to boost/support the underfloor....guess what? With teh UF on 24/7, stat on full the downstairs loo refuses to get above 16degrees on a cold day. Also the coldest area is the area where you sit and chill and I get cold convection from the big window on the extension - not a nice feeling on the neck whilst sat down. Supplementary radiators would have overcome this. But hey, I'm just a customer who knows **** all, when have I ever been right? After doing room calcs, myself - guess what? The UF heating is borderline.

Also word of advice on underfloor, Ive been researching this heavily since I've become aware of teh issues.....make sure the flow and rtuen pipes are ran side by side over their entire length....Polypipe and other UK suppliers seem to show it in a single pipe in zig-zag pattern....this give uneven floor temps, and hence uneven room temperatures.....like this:



Guess what layout I have?

Dingdongler

Because I'm OCD and prefer to do my own homework

He's a decent tiler but I doubt he's done a single area of this size that also happens to have two different sub floors

Dingdongler

Hi Ali

I'm using electric underfloor heating (to keep the floor warm only, there are plenty of rads) and so am no expert on water ufh. However I remember reading somewhere that there are strict recommendations of slowly increasing the temp of water ufh in screed over a number of weeks

Anyway, did you do anything to strengthen the original suspended floor?

(Merry Xmas btw)

stevebt

iTrader: (8)

There really is no need for underfloor heating as a concrete floor will maintain heat in it for weeks and you only need to put kingspan in the timber floor and they will be warm to walk on. I have kingspan in my ground floor and it's quite warm on solid wood floors and barefoot

ALi-B

iTrader: (1)

Yes I read that too. And that's whats worried me - I've no clue of what this muppet plumber was up to whilst I was away. The underfloor was not turned on or used while I was there for 3months after the tiled floor was layed as it was during the summer so hopefully that may have negated any curing processes. I'm just having to wait and see because whats been done is done. Hopefully its just that one tile and nothing else.

Radiators alone wouldn't heat the area, mainly due to the kitchen units and vaulted ceiling area. And I loath to have another noisy kickspace heater (Is everything made by Myson shyte? ). So UF was needed in part of the room regardless.

The joists should have been reinforced, again, I wasn't there at the time, but that was the builder's job so I have faith in him in that area, he's also a master carpenter and what been done on the new structure in terms of support and steels I have no issue with, so I'd expect the same with the floor.

Dingdongler

You're probably right Steve but this area is where the family will spend most of its time so I didn't want to take the risk.

Dingdongler

What is the theory behind that Andy? Is it that the tile will move differently over the two substrates or that the substrates themselves will expand and contract at different rates?

Does the expansion joint have to run directly over the meeting line of the two floors? ie do you have to ensure that a single tile doesn't straddle both kinds of sub floors?

Cheers

dpb

How much does ply expand anyway , when its nailed down ?

i can see not a great idea putting a tile across two different adjoining floor substrates



i must completely miss understood the expansion space youre supposed to put around a solid wooden floor , surely if its all side screwed down its never going expand 1/2 " sideways as a whole

andy97

iTrader: (1)

Simple physics, different materials will expand at different rates. Ideally you would have your joint line directly on the line of the two bases and use an expansion joint there. Flexible adhesive and grout would be my preference. You may be lucky but more likely not.

Dingdongler

Not sure what you mean by the bit in bold. Are you saying that the expansion joint should be made from flexible adhesive and grout??

andy97

iTrader: (1)

Anything tile that has a chance of movement use flexible adhesive and flexible grout. You still will need to have an expansion joint.

imprezagaz

iTrader: (2)

+1. Always used flexible on wooden floors and never had a problem.

Dingdongler

Yes, I see what you mean now. I'm using flexible adhesive mixed with latex liquid

john banks

My big room of tiles is broken up by a change in level so the largest dimension is 8m but all on one poured and well cured screed. There is no expansion joint and there are no cracks through mixed seasonal use. Any bigger and I would have put in an expansion gap. There is a slightly warmer zone at the bottom and top of the steps between the change of level because there are 14 pipes going through 900mm width, but it is not based around the uneven temperatures drawing above. Even the DIY Nuheat brochure informed about this and avoided this error. In a well insulated room the UFH output is generous.

john banks

ALi-B, can you transpose flow and return for some of the UFH coils at your manifold to try to even it out a bit and put the heat where you need it? Easier than lifting the floor to redo or adding radiators? Thermal imaging camera may show the loops and hot/cold spots?

ALi-B

iTrader: (1)

Its all ongoing, John. I could swap a few circuits on the manifold so they are closer to the feed, but that will need some pipes extending to reach.

First I need to stop it getting air in there, as its since become apparent that the routing the plumber chose for the underfloor feed/return from the boiler has created a natural air trap for the entire system (high point with low water velocity)....with no air vent to purge it. I thought after a few months the air would settle and work itself out. I've purged the manifold with the hosepipie as per instructions, but I still hear air going round there and from the feed pipe from the boiler. Its a sealed system that holds stable pressure, so I don't think there is a leak. I need to stop the air issue first before investigating further.

Second after resolving the air, I need to ascertain if there is a problem at design level in terms of layout and calculations they have used (as opposed to mine), or if the plumber didn't follow the plan. Obviously who is at fault will depends on what I find; Can't blame the plumber if the plans aren't ideal, which I suspect is likely that the room usage intent/kitchen layout may have not been passed on - which would explain why the cupboard units make for good plate warmers (and useless for storing chocolate biscuits).

Thermal imaging to map it out would be nice if I could get hold of a suitable camera at reasonable price. All I have is my infrared/laser thermometer. Tried getting my Canon to pick up infrared, but its not having any of it.

hodgy0_2

You must be able to rent one

Dingdongler

A friend rented one recently to try and find a central heating leak, it wasn't prohibitively expensive.