Awkward floor

[jbuk]

My kitchen diner is 9 metres long by 3.6 metres wide

7 metres of the floor is suspended and I'm going to t&g chipboard over the joists, the other or last 2 metres is concrete which isn't flat, I'm going to build a stud wall over about 1.4 metres of the concrete part to make a utility room and a downstairs toilet, I also want to tile the toilet , utility room and about 3 metres or so into the dining room (this will form the kitchen area) the rest of the dining room will be laminate

I've got the joists ready and built them so that the concrete will end up slightly lower (about 5 mm) from the top of the chipboard, this is so I can use some levelling compound to get it flush

my question is really about the best way to level the concrete and to tile between the two areas

my thoughts are to screw and seal a baton across the concrete then level the concrete flush with the chipboard surface then tile directly onto the chipboard and concrete using the appropriate bonding & grout for each surface (or an all in one if there's such a thing?)
the problem I envisage with this is that water could get into the chipboard and damage it (even though it is P5)

my other thought is that I need to put some kind of backer board onto the chipboard to make it water proof then level the concrete flush with the backer board then tile it

if anyone can offer any advice ?

I've so many questions such as, which backer board to use (if I go that direction)
how to attach it?
how much extra will it add to the height of the floor?
which levelling compound?
if I insulate between the joists would backerboard affect the moisture that needs to evaporate from the void thus causing damp and rot?

probably many more to ask as i go along


one final thought is that I should just scrap the tiling and only tile the utility room/ toilet and just laminate the whole dining kitchen area, but I suspect this could lead to more problems with water ingress

 

[1john]

why not make your joists fairly flush with the concrete and then attach battons down them and over the concrete, tap con them into the concrete and pack them so they are level. expanding foam up the voids and then use WBP ply over the whole lot. make sure you seal the ply edges and underneath. This way the entire tiling substrate is the same material and you wont have any varience or expansion and contraction between the substrates. Dont use chip board to tile over. Just my 2p's worth.

 

[jbuk]

HI

The joists are already down and I already had to raise them up an inch where they meet the concrete end, I didn't want too much of a slope

I could level the concrete flush with the chipboard and screw/glue ply to that?

not sure if that brings in its own problems?

 

[tictic]

ok ....
the chipboard even p5.. is.. s h i t for tile fixing to..ok..
first.. what type/size of tile you planning on fixing?
are you having any type off UFH?..

i take it the insulation between the joist will be celotex/kingspan etc..?
if so and you aint planning on any form off UFH, these will need to be flush with your joists..

then overboard with wbp ply min 22-25mm sealed at the edges and underside with a SBR....then screwed down every 150-200mm..

then to bring the concrtete level (5mm) then use a good quality SLC..mapei/F Ball..etc)....fibre based would be best to build it up..

then you WILL NEED TO HAVE AN EXSPANSION/MOVEMENT JOINT BETWEEN THE TWO DIFFERANT SUBTRATES...this is a must!!!!..

then prime the two subtrates with an sbr or an acrylic primer before tile fixing..up the room then when dry across the room(100% coverage)..

you will also want to have an exspansion joint around the perimeter of the room/rooms..

you will have about 35m2 of tiling there mate...have you done any tile fixing before??....

 

[jbuk]

No UFH, it was an idea but I've canned it.

The insulation I have right now is glass fibre, this is what I had planned to use


No tile size as yet, I'm just planning ahead

can the ply be thinner? the joists are at 400 ctrs with 22mm t&g and seems fairly solid , not sure I want to raise the kitchen area so much

the tiled area is about 18m2

never done any tiling and I'll be getting a pro to do this, I'll just want to get the floor prepped for later

 

[Richard C]

18mm WBP can be sufficient in light use/load areas such as bath/shower rooms, depending on joist size/pitch/span but I would not advise anything less than 22mm in a heavy load/use area such as a kitchen, in fact you’d do better to go for 25mm which is the British Standard recommendation.

For the rest of it take careful note of Tictic’s advise; mine would be exactly the same. Bear in mind that not everyone who tells you they are a tiler will know what they are doing or even be capable of laying tiles to an acceptable standard, especially these days; get references & check out previous work in you can.

 

[jbuk]

18-25mm ply on top of the 22mm chipboard?

hmm I'm going to end up with an inch step in the middle of my kitchen/diner which is what I really wanted to avoid really

what about no more ply? will that work?


as for an expansion gap, how would I go about that? do you mean a gap between the tiles on each of the subfloors or just a gap between the subfloors?

 

[IJWS15]

18-25mm ply on top of the 22mm chipboard?

hmm I'm going to end up with an inch step in the middle of my kitchen/diner which is what I really wanted to avoid really

No - you misunderstood them, use plywood INSTEAD of the chipboard.

 

[Richard C]

18-25mm ply on top of the 22mm chipboard?
hmm I'm going to end up with an inch step in the middle of my kitchen/diner which is what I really wanted to avoid really

No you’ve misunderstood as stated, forget the chipboard its total crap; marginally suitable for carpeting over but useless as a tile base

what about no more ply? will that work?

I wouldn’t; ditch the ply & go for 25mm WBP ply straight onto the joists .

as for an expansion gap, how would I go about that? do you mean a gap between the tiles on each of the subfloors or just a gap between the subfloors?

The problem with tiling over two different substrates is they will expand/contract at different rates & even move independently; this will cause the floor tiles to crack where the two meet. This is an expansion joint;
http://www.contractflooringmagazine...ement-joints-in-floor-tiles-why-where-and-how

This link may also be of help;
http://www.schluter.co.uk/2095.aspx

They should be fitted every 6-10m into the tile line & at 9m length, it's desirable to have one even without the different floor substrates you have. It’s a large floor area so you should also leave an expansion gap around the perimeter of the tiles; don’t grout this & cover with skirting. It’s very important you use quality trade tiling materials of the correct type for your tiles & tile base not cheap DIY products which are generally crap. In your case this will be at least a flexible powder adhesive & flexible grout.

Don’t know if you’re aware but new w/c installations must comply with several building regulations regarding drainage, forced ventilation & sound insulation if you use a stud wall between it & a “habitable room”. Creating a new room with a w/c is also notifyable building work requiring a Building Notice submission, inspection & possible witness test by LABC before they issue you with a compliance certificate.

 

[jbuk]

thanks

I did not know the new room would be notifiable although my plan mostly included what the regs ask for anyways

is this a legal requirement or just if I want a certificate?


I will definitely consider going the ply route if i'm going right onto the joists , although i've already got the t&g for the job :/

what about between joist insulation with glass fibre under a tiled floor, is this still ok to do?

 

[Richard C]

I did not know the new room would be notifiable although my plan mostly included what the regs ask for anyways is this a legal requirement or just if I want a certificate?

It’s not a legal requirement but why would you not want a certificate of compliance You will be asked specifically about any building work that’s been done when you come to sell & if you can’t produce the necessary compliance certificate it may cause problems with your sale both from the prospective buyer & the company who is lending them the money. Lying on the seller’s questionnaire is not advisable; surveyors aren’t stupid (well not the good one’s anyway) & if you subsequently get found out after the sale you could find yourself subject to a claim for considerable civil damages; it’s happened. If you are forced to go through the regularisation process to obtain a retrospective certificate, the cost will be 3x the cost of a Building Notice. The Building Regulations you need to comply with & the inspection process is not onerous & I would advise you to submit rather than have the potential hassle of unauthorised building works. Also consider that any future insurance claim may be declared void if the claims assessor believes unauthorised work has any connection with the cause of the problem.

I will definitely consider going the ply route if i'm going right onto the joists , although i've already got the t&g for the job :/

You would be ill advised to use the chip, either return if for a refund, board your loft out with it (about all it’s fit for really) or skip it.

what about between joist insulation with glass fibre under a tiled floor, is this still ok to do?

I would not use glass fibre under the floor; as already stated, use a proprietary insulation such as Celotex, Kingspan or similar; another option might be to use Marmox insulation board or something similar; http://www.marmox4u.co.uk/marmox_insulation.php

 

[jbuk]

thanks

I will phone building control today , i've already got a few notices in so another won't hurt , heh

what is wrong with using glass fibre insulation? I'd like to use celotex or similar but it's so expensive compared to the fibre

what ply would i need, just 25mm wbp structural?

I understand that although p5 t&g is water resistant it's not great for wet areas but out of interest why are people so negative towards it overall?

 

[Richard C]

what is wrong with using glass fibre insulation? I'd like to use celotex or similar but it's so expensive compared to the fibre

Well it’s the same as anything really, good quality insulation materials of the correct type & performance for the job usually are more expensive. I won’t attempt go into why it's not really suitable for floors personally but here's a link which pretty well sums it all up;
http://www.energyvanguard.com/blog-...ems-with-Fiberglass-Batt-Insulation-in-Floors

what ply would i need, just 25mm wbp structural?

WBP, seal the back & edges with an SBR or acrylic primer.

I understand that although p5 t&g is water resistant it's not great for wet areas but out of interest why are people so negative towards it overall?

It’s almost universally used in new builds of which I’ve owned two in the past but you can’t get it up easily if you need to & once you do you can’t put it back again. It starts to move around, creak & groan after a few years & I once hade a washing machine eat it’s way through & fall into the floor void after just 4 years; this was caused by vibration in the back feet alone, no water involved. If you’ve ever had proper floor boards either close boarded or T&G the difference is very noticeable; personally I don’t like chip at all & have not used it in my extensions. It’s cheap & OK for laying carpet or vinyl floor I suppose but it’s unsuitable as a tile base & just doesn’t compare with WBP for rigidity which is essential if you want to avoid tile failure; personally I wouldn’t overboard it either.