Mock Tudor Gable

[Ads17]

We have a mock tudor gable above the upstairs bay window in a 2006 built house.
The makeup of this seems to be a plywood backing board with wooden mock tudor boards attached and an infill of render with metal mesh and pebbledash.

The wooden boards are starting to go in places so we are looking to replace with polyurethane equivalents, however the current boards are 170mm wide and the nearest size option in polyurethane is 175mm. So to get these to fit we would need to trim the edges of the pebble dashed infill a few mm to accommodate the slightly wider boards.

Should this be straight forward with a grinder and diamond blade or is it likely to cause any damage to the pebbledash which appears to be in good condition?

[wolfracesonic]

I shouldn’t damage the pebbledash as such but getting a clean cut on pebbledash can be tricky, the pebbles do their best to slightly deflect the blade.
If you go ahead, screw a batten to the existing timber board to fun the disc against. If you remove the waste first, there will be less chance of damaging the remaining pebbledash when you pry off the old boards.

[dingg]

Trim the new board by 5mm ,surely the easiest option?