Hi all. Rendering a newly built house the past week or so. Scudded 2-1. Scratched 4-1 with evoplast waterproofer. Nap finish at 5-1-1/2 with evostik plaz. Scud and scratch went fine but the finish is baffling. Scratch would be wet down the evening before a couple of times and again in the morning wet down 2 r 3 times before applying finish coat. Elevations would be nice and damp. The problem is when we go back screeding there are dry patches and wet/moist areas. Dry patches are about 12-18 inches square and are going "crusty" while other areas are as I said holding well for a float. It's not where the sun/wind are hitting the wall because some parts are in shaded places. We are thinking maybe it's a s**t waterproofer or the sand is dodgy. Anyone ever come across this before. The walls are wet down consistently so it's not because areas are missed when wetting down. Usually only 2 r 3 spots the size of a football on a decent size gable....? Again I stress the walls are wet down consistently well.
Rendering problem
- Thread starter solway
- Start date
From October to end of March we would use plaz in scratch and w'proffer in finish. But from April to Sept/Oct it's w'proffer in scratch and plaz in finish for "suction control"(my arse). Happened last year aswell when using w'proffer in scratch,never happens when plaz in scratch. Iv read reviews on evoplast w'proffer and the reviews are not great....its the green slimey stuff. It's what's stocked here 90% of place's.
Nicm
Well-Known Member
We use the Bostick waterproofer now seems to be the best lately.Evoplast used to be good a few years ago but seems more diluted now and weaker.As regards the issue with the dry spots it may be when you straight edge the wall the scratch coat may be over a bump in the wall thus leaving the finish coat very thin in those areas.Even if the wall is wet consistently you have a finish coat of different thickness drying at different times.
No all fresh blockwork(5newton). No bumps in scratch because we always screed/straighten scratch coat aswell.
Just on the conc blocks Flynnyman I have a bro in law working for a concrete plant. His role was to mix the concrete for foundations/footpaths and blocks. Boss man comes through the door 1 morning while he was mixing up a batch of concrete for a raft foundation. He says "Jesus Christ do you know the price of cement these days" and turns down the volume of cement required. When he leaves the bro inlaw turns it back up to the proper amount. The funny thing is all his products/concrete are certified.......so we think.
I will have to change waterproofer/plaz as all we have here usually is evoplast or evostik. I also on occasion see here, Larsen/everbuild/Sika. When ordering materials the client/builder 99% of the time buy them.
Just on the conc blocks Flynnyman I have a bro in law working for a concrete plant. His role was to mix the concrete for foundations/footpaths and blocks. Boss man comes through the door 1 morning while he was mixing up a batch of concrete for a raft foundation. He says "Jesus Christ do you know the price of cement these days" and turns down the volume of cement required. When he leaves the bro inlaw turns it back up to the proper amount. The funny thing is all his products/concrete are certified.......so we think.
I will have to change waterproofer/plaz as all we have here usually is evoplast or evostik. I also on occasion see here, Larsen/everbuild/Sika. When ordering materials the client/builder 99% of the time buy them.
CeeVee
Well-Known Member
I like everbuild the best. Never tried larsen but always have trouble with sika.
i think you have not added the waterproof additive correctly.
we mix the waterproof ad. into the water bucket and stir with an off cut of angle bead it then runs through the sand and cement evenly.
if you just pour the waterproof into the cement mixer you will get dry patches as it does not run completely through the gauge.
when you hose the wall down the next day you are washing the waterproofer out of the gauge. leave the scratch coat for a week to cure.
we mix the waterproof ad. into the water bucket and stir with an off cut of angle bead it then runs through the sand and cement evenly.
if you just pour the waterproof into the cement mixer you will get dry patches as it does not run completely through the gauge.
when you hose the wall down the next day you are washing the waterproofer out of the gauge. leave the scratch coat for a week to cure.
