rendering

[sharky]

Hi
Can anyone tell me if you need to pva a semi engineering brick to take render?

Many thanks

 

[pwi]

Pva has no place in external rendering so either sbr slurry or hpx and mesh

 

[Chris W]

nope, mechanical key being the best...

 

[carlos]

I have no idea what hpx is

 

[church]

Here you go Carlos http://www.k-rend.co.uk/range-view.aspx?title=K Rend Base Coat Products&dataid=234866

 

[S a plastering]

rendaid then top it over with ocr

 

[pwi]

I think one of the mods need to put somthing in the tips section about pva used externals

 

[spunky]

it needs a key depends on what youre rendering it with

 

[carlos]

thanks church

 

[Journeyman]

Class 'B' engineering have little suction so I tend to either 1) Apply SBR/cement slurry with a soft hand brush in a stipple pattern 2) Fix expanded metal lath with Hilti nails or stainless penny washers and screws 3) Grind out the horizontal bed joints to 10mm.
Sometimes a combination of the above, depending on the specifics of the job.

 

[flat boy skim]

sub it out 8)

 

[kirk johnstone]

there are lots of ways to get a key but i find the best way to do it is to rake out the joints (angle grinder with masonry disk) fast, good key and cheap

 

[RMK]

I'm new to rendering, so I apologise in advance for my neivety, but why do you need to rake out joints? I know to create a key, but doesn't the pointing alone give something for the render to bind to?

 

[kirk johnstone]

I'm new to rendering, so I apologise in advance for my neivety, but why do you need to rake out joints? I know to create a key, but doesn't the pointing alone give something for the render to bind to?

i would say that if you were working over a rough faced brick then no dont bother cutting the joints out but if the face is glazed then i would strongly recommend it, the joints are normally finished to let water run down the wall and not sit in the joints therefore it will have the same affect on your render.

oh and always wet the wall down before plastering, the water acts like flux and will bind the two materials together. if you soak the wall it will have a shine or a glisten on it from the water, as soon as this disappear's start rendering

 

[Render Systems]

there are lots of ways to get a key but i find the best way to do it is to rake out the joints (angle grinder with masonry disk) fast, good key and cheap

I agree with Kirk on this one but i would also roughen up the brick face with angle grinder held at 45 degrees... if you use pva it would be like floating a bloody mirror