Spreader plate floor covering - 10mm ply?

[blankton]

I have just installed some spreader plates for a wet UFH system. Due to the existing floor being uneven and noisy, I have build a framework of 3x2 CLS at 400mm centres. The attached datasheet gives heat output with two floor coverings - wooden floor or 10mm ply and carpet.

 

Have I misunderstood this - the manufacturer is recommending 10mm ply as the deck on top of the spreader plates. I can understand that its best to keep it as thin as possible, but 10mm seems very thin. We have tried a sheet and put a lot of screws into it, but if you are between the centres, it does depress slightly. The small amount of deflection would probably not be noticeable, but I am concerned that this repeated movement might eventually cause the pipes to wear or fatigue. After the mammoth undertaking of fitting this system, I'd like it to last  very long time and not be pulling up boards due to leaks in a few years time. 

 

So - am I worrying over nothing? Have I misunderstood the manufacturers spec? Has anyone used 10mm ply in this application before. If not, what should I use. I guess if I stick with ply I can keep it thinner than chipboard (22mm) as its stronger. 15mm, 18mm? 

 

Many thanks for any advice. 

 

 

[ProDave]

I used 12mm ply as a floor at 300mm centres for the mezanine (I wanted to minimise floor build up) and I thought that was pushing it.

[saveasteading]

I reckon 10mm of good quality is fine, just. To deflect it has to compress or stretch, and it really shouldn't if fixed tight.

What do you mean by ' lots of screws'? 200cc?

 

But the heat barrier of another 2mm will be very little. 

 

The underlay for ufh is expensive, and the carpet has to have an open backing too. That will matter more than 2mm of ply.

[blankton]

3 minutes ago, saveasteading said:

I reckon 10mm of good quality is fine, just. To deflect it has to compress or stretch, and it really shouldn't if fixed tight.

What do you mean by ' lots of screws'? 200cc?

 

But the heat barrier of another 2mm will be very little. 

 

The underlay for ufh is expensive, and the carpet has to have an open backing too. That will matter more than 2mm of ply.

about 48 screws on a 8 x 4 sheet.