Karndean prep to timber floor

I am informed that with Karndean, any preparation is to be finished with Karndean Skim Coat.
On a poor floorboarded sub floor, is it considered best practice to:

a/ Ply floor with 6mm, screed over, then skim coat.

b/ Ply floor with 9mm, then skim coat.

c/ Some other method.

Your reasons for your answers would be appreciated.
Thanks in advance.

 

I usually 3mm sp101 and then flexy the lot

 

On poor timber floorboards I always 9mm ply atleast or 12mm. Then feather .

Or

C/ use versalay system

 

The problem with using 3or 6mm ply on a poor floor boarded subfloor is that the ply will follow the bend and curves of the boards . In really bad cases even a flexi coat over still follows contours. Best bet is to use a thick ply screwed down securely ,then a feather on top . In past I've used two lots of 6mm on top of each other staggered to give a nice solid subfloor. Then the joints arnt so obvious. Feather on top and it's spot on mate. Prep is everything as the lads will tell you on here.

 

Really bab floors run a sander over it on the 45 degree then ply and flex

 

If its really bad then sink and nails, plane off high spots, min 9mm ply then feather finish. If worse than that, then flex over the top too.

 

6 or 9mm ply screwed down depending on how much light and how bad the subfloor is then flexable levelling compound over the top. Not 3mm coat tho! Enough to level it out!

 

And do you all use the Karndean skim coat as a final application? I ask because I have been told that the guarantee is invalid if this is not used. Is this correct? Is this product a form of screed or a sealant?

 

are you an installer?

 

I wouldn't be surprised if karndean say that. Typical of them , like there skim coat is any better than ardex feather ?, guarantee is worth jack s##t anyway .

 

Sorry mate if you are referring to karndean saying you must prep over ply with skim or feather , then you are right , they do insist on it .

 

Are you a floor layer?

 

You can do everything karndean tell you to do for there warranty but they will still send you materials that dont fit the best

 

Thanks for all the answers.
I am a very experienced carpet fitter who is buying a carpet and flooring business. I know little about lvt's and I am attempting to learn as much as I can about Karndean before talking to the employed floorlayers. The business sells a lot of this product and I've just found out about this skim coat they supply.
There seems to be a variation as to how to achieve the best prep. A floorlayer who installed Amtico to the company I used to sub contract to, used to fit 9mm birch ply and then put a 3mm expensive Uzin screed over. It was like glass and the best I have ever seen but it worked out hellish expensive.
I am looking for a cheaper equivalent finish. The application of three materials prior to installation sounds crazy.

 

I'm sure you are well aware amtico is an expensive product so taking short cuts in prep isn't a good idea . Unfortunately good preparation is necessary and fairly expensive but it's better to get it right first time than to rip it up due to poor prep work.

 

Make sure you use a good plywood mate, this last year all I've used is SP101 6mm or 9mm plywood.
Really good gear.
If you spend a big of time sanding floorboards or filling holes before you put the ply down then feather / skim coat the plywood you should be ok on most jobs.
On bad subfloors though you are best plywood then a wood fibre reinforced screed.

 

Get yourself on a few courses it works .