Screed on chipboards

[Anthony30]

Hi.

We are currently doing the bathroom up and laying porcelain tiles on the floor but have found the floor not level by approx 10mm over 600mm length. We have PVA bonded the floor and layed screed - we had to put a second coat on top of the first but the second coat was a lot runnier - is this going to cause any problems???

Thanks

 

[mattysupra]

what screed did you use?

 

[Anthony30]

Hi. Many thanks for your reply. I used Febflor Plus self leveling screed. What it is, the chipboard floor in the bathroom is arced so to speak and it dips about 10mm over a 600mm level (there must have been joist slightly higher when the house was built and they have nailed down the chipboard to contour the joist).

Yesterday I mixed some screed and poured it over the floor (I believe I should have put plywood down before I did this but that is to late now).

Once it was dry enough I put the level on it just to realise it was still out. This time I mixed more screed and poured it over the area in question. The second batch was slightly more watery but it has solved the problem of the dip. The colour of the second batch of screed is a lot more of a lighter grey than the first batch. Will this cause any problems in the future?

Many thanks

Anthony

 

[mattysupra]

you may be lucky, but you have done a few things wrong. Unless your going to start over i wont scare you with the problems you may have. Unless you want me to??

 

[Anthony30]

Go on tell me what I have done wrong and what the aftermath is if I was to carry on

Thanks

Anthony

 

[mattysupra]

First problem is that the compound is not suitable to lay over flexible subfloor. There is a chance it will start to crack, and then separate parts move up and down from each other.
2nd problem is that you went over chipboard and not plywood. Chip board does not have a strong shear strength and the compound may come away from the chipboard.
3rd problem is that if you have not mixed correct and are left with more of a white powder colour you will have weakened the shear strength of the compound. Which can lead to your tiles parting from the screed.
4th problem is that the chipboard will suck up the moister and start to grow. Worse case moving stud walls , w.c etc with it. ( but dont worry. only seen this happen on large areas. )
So up to you if you chance it or start again. If starting again, take up straight away to minimise amount of moister getting into chipboard. Good luck

 

[Anthony30]

Many thanks for your swift reply.

Just so you know I used PVA prior to screeding. Would this eliminate problem 2 of your last post?

The area screeded in the bathroom is 1800mm by 1400mm. Would this small space be a problem?

How would u recommend lifting the screed? The first batch went down yesterday at about 3 o clock GMT and the second at 9 o clock pm

Also what other screed would you recommend

And lastly what would you do if you was me.

Cheers

Ant

 

[mattysupra]

Still going to have shear problem and if i was you i wouldn't of done what you have done! To be safe i would start again. Thing is if i do a job for someone i have to guarantee my work, so if i come accross this problem the customer has to pay me to do it properly or i wont do the job. In a diy job you only have yourself to blame. Its on your back if you risk 30 quid of screed over a few hundred of tiles! But still every thing may work out o.k??If you read the sticky at the top about how to level a very uneven wooden subfloor you will find how to do it correct and products here. Let me know if you need anymore help.

 

[Anthony30]

Ok ill do it again. I am going to get my work gear on. I would appreciate it if you could tell me what to use to get the screed up. Any tricks of the trade

Many thanks for your help. I suppose doing it this way I will have confidence it being done properly.

Cheers

Ant

 

[mattysupra]

large very sharp scrapper. Will fly up. When you have it up put fan in room and leave a couple of days before re trying.

 

[Anthony30]

Mattysupra, You are a superstar. I will let you know how it goes. Many thanks for your help. I am sure you have saved me a few hundred quid down the line somewhere.

Im getting started now.

Cheers again.

Ant

 

[Moz]

"uk captain of european floor laying competition. finishing 2nd place in europe."

screed on wood ..????

give yer Mickey Mouse trophy back an excuse youself ...

floating floors need to be levelled up on a timber substrate ..duh

 

[mattysupra]

really? And you are ?

 

[Moz]

mattysupra
me just ....
a Professional tiler that had one of the biggest bathroom fitting firms in Manc ...
20 odd years on the tools
I forgot more than you know ...

have YOU ever read the building regs ?
floating substrate floors need to be levelled up on a timber substrate
straight from regs ...
an you say
screeding a suspended timber substrate is ok to tile on ??????????

 

[mattysupra]

Funny people who say they have been it the trade for 30+ years come to me for training. The biggest companys in europe ask me to develop and test + train for them .And i wonder who was involved with writing british standards and nvq's ?? Your behind the times. And who said it was a floating floor? I guess that 2 of the biggest floor levelling companys in europe dont know what they are doing when they sell a product made for levelling a wooden subfloor? And why be so rude? Someone says they have levelled a floor with compound , asking if done correct and when i try to help them , you come out with that rubbish. Not that you dont agree or i have not heard of this method, can you tell me more! Im not saying dont rip out your bathroom and struggle to take up chipboard with stud walls on top. They have already decided how they want to do it. And let me guess( you should put down 25mm of plywood)! If they already have 18mm chipboard + 6mm of ply with 5-10mm Very dense fibre reinforced smoothing compound, How solid is the base going to be? Maybe you should re-cap on todays methods. And i dont care how big your shop is or was , every wondered what i might have? I guess you get flown around the world showing new methods, in most months flooring magazines and known to every one who is a top man in the trade. Or is that just me