Rendering Advice

[grim_d]

Had a search on google but cant decide what to go for.

Have bult a small retaining wall from dense block and want to render it, i was thinking of doing a 2:1:1, (soft sand, sharp sand, cement) for the scratch coat and a 3:1 (soft sand, cement) for the top coat, then paint with a good outdoor paint.

What about a sealer or anything on the blocks beforehand?

Does this sound about right? I keep seeing lots about adding lime/plasticizers but i think it's unlikely to do much moving as the ground is very settled and I used strong mix for the entire thing

Any help appreciated!

ta.

Edited by grim_d on Wednesday 24th June 17:00

[mrmaggit]

Seal the blocks beforehand and the render won't stick.

[Slagathore]

I always thought a mix of PVA and water should be applied to the surface before rendering?

Not every time, though. As I remember jobs where we haven't needed to do it before rendering?

ETA - forgot to say, we always put lime in the mixes.

Edited by Slagathore on Wednesday 24th June 20:28

[V12Les]

You can(if you must) put PVA in the mix but no need to paint on the blockwork. 3:1 is to strong a mix, 4:1 is plenty strong enough. Dont use building sand, use plastering sand. Add waterproofer to both coats.

[grim_d]

V12Les said:

You can(if you must) put PVA in the mix but no need to paint on the blockwork. 3:1 is to strong a mix, 4:1 is plenty strong enough. Dont use building sand, use plastering sand. Add waterproofer to both coats.

I wont bother with a sealer or anything then, whats plastering sand?, washed soft sand? any idea how much more it is than builders sand? Just as i have to pay cash!.

[V12Les]

Plastering sand is slightly grittier than soft building sand, and is slightly cheaper too!. Tip: when its ready to float up, lightly finish with a firm sponge in a circular(ish) motion, keep the sponge clean by rinsing out in a bucket of water.

[grim_d]

V12Les said:

Plastering sand is slightly grittier than soft building sand, and is slightly cheaper too!. Tip: when its ready to float up, lightly finish with a firm sponge in a circular(ish) motion, keep the sponge clean by rinsing out in a bucket of water.

ok, could i not just use a mix of building and sharp sand as i have some of them lying around?

do 2 coats of the same mix?

[V12Les]

Building sand shouldnt be used in render. Yes, two coats of the same mix.