Rendering over scratch coat

[James189]

Please help. I'm rendering a extension it's thermolite block and I've put the scratch coat on but that was a week ago now and when I did 1 site it dryed very quickly and some bits just peeled off. I realise it was too dry but not sure how much water to put on the scratch coat first? Please help

 

[Micilin]

First of all Is the remaining scratch coat sound ?

If it is perished you willl have to take it off - or at least anything that is loose or dusty.

 

[James189]

Thank u for such a quick response yer it seems to b sound.

 

[peaps]

If it's sound get your hose pipe out and give the wall a good soak.

 

[peaps]

You can tell how much when you look at the water soaking into the wall. When it freely runs down the wall you are ok to go. Remember to keep an eye on the job as you go because it will drink much water. You may need to wet the wall as you go along.

 

[James189]

Sorry to keep on mate but will it matter how much water cas will too much stop it sticking

 

[peaps]

Sorry to keep on mate but will it matter how much water cas will too much stop it sticking

No too much will not stop it sticking but you will not get away with putting it on heavy, take your time with it and don't put it on in lumps. you will find that there is some suction and as you go you will find it's still drinking although slower. If you do put enough water on it will crack and lift. Your scratch coat will give it enough key so don't worry, soak the wall.

 

[James189]

Thanks so much mate. When I done the drip beads should they of completely covered the damp course.

 

[mac391]

The drip bead should always be above the damp course. Also your final coat should be weaker than the scratch coat, i.e less cement. If a5/1 mix was used in the scratch then a 6/1 should be used in the finish coat.