hairline cracks in render

[roughas]

just wondered if any of you guys could help not far off oasis thead but the few bits of rendering ive done seem to turn out nice but do have a few hairline cracks when dry have asked other spreads and they say its normal and just happens but it pees me off i want perfection,just wondered what you guys thought? cheers

 

[ziggy2]

What sand do use mate? Do you dampen down before applying your render to control suction?

 

[flynnyman]

And what mix?

 

[church]

Are the cracks visible when the render is dry or can they be seen after the walls have got wet ? Also what have you been rendering over ?

 

[Liam Murray]

what was the background, and did you use building sand for the rendering

 

[roughas]

just use whatever plastering sand i get hold of tp last time it was a bit rubbish i must amit,left scratch 2 days dampened it down a bit didnt pull too quick. 4/1 scratch 5/1/1 top and was on concrete blocks last time and the cracks are visable when dry,cheers.

 

[essexandy]

Is your scratch coat thicker than your top coat? And about what thickness is your top coat?

 

[church]

As you can probably tell there can be quite few reasons why render hairlines my guess is that if the render does not sound hollow when knocked its shrinkage also thickness of render

 

[roughas]

usually each my my coats is about 10mm its not hollow so prob is shrinkage paints up fine tho just when i see it when its dry the little hairlines annoy me

 

[spredz]

usually each my my coats is about 10mm its not hollow so prob is shrinkage paints up fine tho just when i see it when its dry the little hairlines annoy me

How long did you wait between the scratch coat and the top floating coat? Also did you use any lime in the top coat as it reduces the risk of cracks as it helps retain the moisture longer allowing for less shrinkage (more relevant in the summer especially)

 

[bodplasterer]

Also try adding fibers to the mix you can get 2 grades for scratch and top coat.