Rendering

[Corky47]

I'm rendering 3 bricked up windows approx 1m x 1.2m each I've put water proofing in the first coat with out thinking and now the 2nd coat won't stick due to lack of suction. Is there anything I can do to avoid hacking off the 1st coat. Help please.

 

[Micilin]

I'm rendering 3 bricked up windows approx 1m x 1.2m each I've put water proofing in the first coat with out thinking and now the 2nd coat won't stick due to lack of suction. Is there anything I can do to avoid hacking off the 1st coat. Help please.

The second coat will stick,lack suction has nothing to do with it. The lack of suction just means it will take longer to set - also, it will set properly rather than just dry out

. Have you keyed with a scratcher?

Perhaps you have left the first coat too far back, so your second coat is too thick. a coat of 8-10mm is what you are looking for. What is the mix you are using?

You should be putting waterproofer in your scratch coat if you want your bricwork sealed up, using w/p was not a mistake.

 

[wozza56]

Waterproofer is meant to go in the scratch coat so i dont know what you are doing wrong ,you did scratch it didnt you ? and by not sticking what do you mean ,is it rolling off or just sliding off ?

 

[external]

o dear w/p =no grip ,old story,if your gonna stop the suction make sure you have a a strong mechanical bond ,ie a deep scratch,after all thats all thats holding the two coats together!

 

[Corky47]

thank you for your replys they have been very helpful. I did scratch the 1st coat the 2nd coat stayed on but sounds hollow, It was a very hot day though and I also put waterproofer in the 2nd coat was this ok

 

[roy c]

That was ok but not necessary, it sounds like the second coat dried out too quickly. in hot weather you have to keep the work sheeted and keep the cement hydrated by spraying it and keeping the work damp,but not over exsessively wet..Not easy to do in some case's. All last week I went back on the evenings to spray the work I had done during the day,,,

 

[roughcaster]

That was ok but not necessary, it sounds like the second coat dried out too quickly. in hot weather you have to keep the work sheeted and keep the cement hydrated by spraying it and keeping the work damp,but not over exsessively wet..Not easy to do in some case's.

All last week I went back on the evenings to spray the work I had done during the day,,,

And that's what makes all the difference as Roy said. You really have got to keep the moisture in the render for as long as possible during hot spells, or it'll just dry out and powder away.

 

[external]

or you could try the old trick of not using waterpoofter,saturate the wall the day before and damp down before you top ,i now it may sound old fashioned but trust me it will work
edit to say.this way the water comes back thru the render,stops it drying out untill the sets done,which id give a day or two,you wont keep an 8mm coat on wp scratch damp for that long unless you sleep with it.
been nice educating you