External render - width of board and render coats

Hi!

We are building an extension with external render going onto a wooden frame. We have 20mm space between the wooden frame and the boundary with our neighbour. Our architect is recommending K-Rend with specs of 12mm cement particle board, a 4mm first coat and 8mm top coat. 12+4+8=24mm and a big problem with the neighbour! The stud wall is already in place and we don't want to move it back if at all possible. Has anyone any suggestions about a lighter render and/or thinner board that would give us the extra 4mm we need?

Many thanks

jimmyb67 said:

Hi!

We are building an extension with external render going onto a wooden frame. We have 20mm space between the wooden frame and the boundary with our neighbour. Our architect is recommending K-Rend with specs of 12mm cement particle board, a 4mm first coat and 8mm top coat. 12+4+8=24mm and a big problem with the neighbour! The stud wall is already in place and we don't want to move it back if at all possible. Has anyone any suggestions about a lighter render and/or thinner board that would give us the extra 4mm we need?

Many thanks

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At first glance , it seems like your architect has left you a problem with the space which there was no need for, if you only have 20mm to play with left.

He should be coming up with a board for you , as in fairness he knows what thermal, weatherproofing and structural issues are important.

Hopefully someone else will help you , but off the top of my head -

I would have thought his K rend first coat is to mesh the boards, like a rendaid product. It will be hard to finish Krend with 8mm anyway. You will be looking at using 10, 12 or 15mm beads. 15mm are standard.

You could try STO render, which beds mesh in a first coat of 3-4 mm, and top coat of 2 or 3 mm. (It was on Grand Designs last week , although they made a mess of it). It is a good product if used properly. I have used the 1mm finish coat, but inside on ceilings and it is less forgiving than the 2 or 3mm finish.

Trowel tex is similar, a meshing coat (3-4mm) applied one day, and thin final coat with primer, 2-3mm, the next day.

You could possibly Rendaid the lot , nice and flat covering all the mesh , and then use Hi Build.

Thanks, Micilin. Our neighbour has disputed where the boundary is, which is what has caused the problem and meant we need to be flush with the existing wall rather than step out slightly. Will take a look at your suggestions.