Fixing Plywood onto Concrete

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Hi

I am planning on laying an Amtico floor in my lounge and through to an extension. The lounge has a wooden floor whilst the extension is concrete and ever so slightly lower.

I have read the stickies and a few other artiles on preparing the subfloor. As I will be fixing 6mm WBP ply to the wooden floor in the lounge this will cause the gap in height from the concrete extension straight to the lounge to be around 7-8mm which is a lot to level our for a newbie! Can I lay ply onto the concrete extension as well and then screed the odd 1-2mm difference so the two floors are the same height? If so can the ply be fixed to the concrete with adhesive or is it best to screw in?

Thanks
Paul
 
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Firstly, please reconsider doing this yourself!!!!

This is a very expensive floorcovering that installed correctly gives many years service. However laid badly it causes no end of grief.

You have done some homework and your post shows that you have already realised that correct floor preperation is absolutely vital to the sucsess of this type of flooring. In my opininion laying the tiles is the easiest part of the job, and I agree that 99% of the DIY population could handle this part of the job.(cutting them accurately is a different matter!!)

However fixing the plywood correctly is quite a skill in itself - if you muck it up your floor will pop-up very quickly. never the less a half decent DIY-er should be able to do this also.

Screeding to a good standard is not however a skill you can pick up easily - it takes years of experience to judge correctly - it involves many aspects of knowledge including moisture levels DPM`s etc - if this were for a carpet or cushion floor vinyl then I accept you may get away with it
BUT - for this type of flooring getting it right is critical.

The internet is full of sites selling Amtico/Karndean very cheaply and once they have your money you get a delivery of boxes. However most Independant shops will sell you the same stuff for the same price. What you are now realising is that 50 -75% of the cost of this flooring is for adhesives, screed/board and labour.

By the way also be wary of the bloke in the pub who has been "on the course" - If they are any good why arent they doing it for a living??
 
Thanks for the info, yeah have done the bathroom floor before which was Karndean so have a bit of experience but to be honest I just enjoy doing doing these kind of things so really want to give it a go!

I theory would it be OK to ply on top of the concrete floor as well and then get the two levels the same with superflex 700?
 
The correct reply is no - you should screed in several layers until level

However, you will find it difficult to know exactly what your height differences will actually be until you start. (i.e. have laid the ply to your wooden section)

...you will hopefully get it level with two screeds (let the first one dry properly first)

I am not a fitter, so have no experience of actually laying a screed, but have enough estimating experience to know that there is usually a way.

Talk to your screed supplier once you know the exact thickness you require and he will reccomend a system suitable for you
 
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OK looks like better option would be to ply the wooden part of the floor then for the concrete area:

1) Prime current concrete floor with P131
2) Add screed around 3mm of F-Ball Stopgap 300 HD
3) Prime with F Ball P131
4) Add DPM of F Ball P46
5) Prime again with F Ball P131
6) Final screed to get level with through lounge (lined with ply) of Stopgap 300 HD.
7) Prime with F Ball P131 ready for Amtico Adhesive

Does that look OK?

Thanks Again
Paul
 
Looking into this for stage 2 maybe better to use Stopgap 900, does this sound OK to the experts out there?
 
OK looks like better option would be to ply the wooden part of the floor then for the concrete area:

1) Prime current concrete floor with P131
2) Add screed around 3mm of F-Ball Stopgap 300 HD
3) Prime with F Ball P131
4) Add DPM of F Ball P46
5) Prime again with F Ball P131
6) Final screed to get level with through lounge (lined with ply) of Stopgap 300 HD.
7) Prime with F Ball P131 ready for Amtico Adhesive

Does that look OK?

Thanks Again
Paul

step 2- use acrylic 200 or 900 under a DPM. But do you need a surface DPM? Have you taken moister readings of the subfloor or are you doing this as a safe guard? Its alot of money wastred if you dont need a surface dpm.



I would plywood the wooden area. Then get a rapid repair mortar (400) and creat a ramp upto the plywood. Then skim the concrete section with 200 acrlic primed with 131 mixed at 4/1 with water or 900 with no primer. (i dont like 900 and the lack of primer, it can cause pin holeing that you dont want.

Next apply epoxy dpm if its needed?

Then neat coat of 131 and skim over the concrete and wood section with 700 flex.

You should have a perfect subfloor.


Here is a step by step guide i done with pictures for another forum, you will have to sign up as a member i think to view but i think it would be worth it for you- http://www.theflooringforum.com/viewtopic.php?f=32&t=368


Please note that a flex compound was used from the start as dpm was not needed, if a dpm was needed i would of done the skim in acrlic and then a final skim of flex
 
Wow great guide thanks!

Couple of questions - am I right in thinking to leave a slight gap between the ply and to then fill this with caulk as per your other guide to stop the levelling compund dripping through? Also just to confirm the Flex 700 is ok to use as a final coat on both the ply and concrete sections? One more what adhesive would you recommend to stick the over lapping ply to to concrete?

Thanks again for a superb guide.
 
caulking is needed to fill any 'small' gaps before your poor the compound over the top. However if you have a height difference between the two floors like you do you need to creat a ramp out of a mortar (400). You mix this stuff thick so it wont run, hence no need for caulking, you can fill any dips, cracks, gaps etc with this first!

BUT, you defo need to make sure there are no gaps before you lay the final compound down. Its like water so will disapear down any gaps.

As for gluing the plywood onto the edge of your concrete you need something like ' no nails' or simular.


Did you look at that link i posted up? there are pictures of me ramping with 400 onto the edge of the plywood on there along with filling dips and how to etc.
 
Yes thanks for the link was really helpful with the pictures too!

With the gaps I was just thinking if an expansion gap is left between the ply boards when laying and around the wall?
 
as lond as you acclimatise the plywood (exterior grade/wbp) and your the correct fixings it wont need expansion gaps between the boards and it will only need a matter of 2-3 mm around the edges of the room. This will be fine to fill with caulking as it will compress.
 

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