Recycled Plastic Lumber Or Timber Fencing?

[JtB]

A local fencing contractor has suggested concrete slotted posts with concrete gravel boards and Treated C24 Carcassing Timber Boards (1830mm x 150mm x 47mm) screwed into vertical timber rails per the following diagram:

View attachment 737896

Searching the internet I don't seem to be able to find any examples of this type of fencing construction. The closest I can find is "acoustic fencing", however this uses timber boards which are tongue and grooved. The main concern I have therefore with the above fencing construction suggested by the fencing contractor is that if the individual timber boards start to bow/warp over time, then gaps will start to open up between the individual timber boards because they are not tongue and grooved. Admittedly the individual boards will be screwed into vertical timber rails, but I'm not sure if this will be sufficient to prevent significant gaps opening up over time.

I'd appreciate therefore the opinions of anyone with knowledge / experience in this area.

Another concern I have with this design is whether the weight of 15 substantial timber boards on top of a concrete gravel board is going to cause the concrete gravel board to sink into the ground.

If the fence was constructed from feather edge boards attached to arris rails then the weight of the fence would rest on the posts instead which are firmly concreted 1 meter into the ground.

 

[Randomnerd]

As a mobile sawmillers in the winter months: sweet chestnut would be rotproof; larch and Douglas fir would last 20-25 years untreated.
We install posts direct in the ground with no concrete, no plastic coatings - drainage is a key factor installing good fencing.
I'm a drystone waller for the better seasons: stone boundary at 72" high would be circa £400 per yard.

 

[rogerzilla]

Wooden fences are fine, wooden posts are not. One of the 4" posts installed in my back garden (by professionals) in autumn 2015 has already rotted right through at the base. Concrete posts cost more to buy and to have installed, but they don't rot.

Slotted posts with panels can rattle in the lightest breeze, or the panels can bend and flip out in stronger wind. Best to have drilled concrete posts to which the horizontals are bolted.