Karndean directly glued to Screed and 22mm particleboard

[NewToAllOfThis]

Hi,

 

We have UFH with liquid Screed on the ground floor that has been sanded to remove laitance. We are looking at having Karndean flooring. W

 

On the first floor, 22mm Norbord “Cabershield+” particleboard with a heavy duty PU coating on 600mm wide Posijoists.

 

We have just had our first quote for installing Karndean and they want to lay ardex primer and a 3-4mm coat of ardex N/A latex screed.

 

On the first floor they want to lay 6mm ply on the 22mm particleboard.

 

Is it correct, or could the Karndean be laid directly on to the floor surfaces?

[Nickfromwales]

3 minutes ago, NewToAllOfThis said:

We have just had our first quote for installing Karndean and they want to lay ardex primer and a 3-4mm coat of ardex N/A latex screed.

 

On the first floor they want to lay 6mm ply on the 22mm particleboard.

 

Is it correct, or could the Karndean be laid directly on to the floor surfaces?

All 100% correct. Fail to prepare, prepare to fail.

The screed is a feathering compound which rids the floors of all imperfections, without it you will see every divot made by the laitance-removal machine head.

The ply could be thicker TBH, but that will also need the joints and screw holes filled, feathered and sanded.

Sounds like you have the right guys for the job. 

[Hobbiniho]

i presume that your liquid screed floor isnt perfectly flat?? there is no real need to use latex on a concrete floor but they are maybe taking a belt and braced approach, the plywood is needed and should be glued, nailed at 4" grids then a latex acreed applied over the top dont underestimate how little it takes to show a flaw in karndean, if it isnt completely snooker table flat you will see the flaws