rendering

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GDS

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what mix dose every one use for rendering on a out side wall and the scractch coat, how much waterproofer do you lads put in per mix? out side wall block of flats
 
all depends on the substrate mate,the harder the surface,the stronger the mix,say ordinary concrete blocks ill use 5-1-1 scratch an top with 6-1-1,thats lime by volume not weight,if you dont use lime just the same exept ad waterprof-admix per spec.
 
Waterproofers vary aswell different makes different amounts it normallys says the amount to use on the tub.
 
Waterproofers  vary aswell different makes different amounts it normallys says the amount to use on the tub.
wise words,seen more render fkucked up by overdose of admix than anything else!
 
SO THATS 5 SAND 1CENTENT 1 LIME FOR SCRATCH?  LONG DAY MATE PATCH WORK ALL DAY !!!!!!!
thats it mate ,i must admit to lashing half a gallon of pva to every 50kg of torment in with a patching mix ,seems to stop any cracking.
 
Waterproofers  vary aswell different makes different amounts it normallys says the amount to use on the tub.
wise words,seen more render fkucked up by overdose of admix than anything else!
What tends to happen if you overdoes on the admix???
tend to have the consistancy of a digestive biscuit,ie not set an very sandy,it will allso suck the water out of the top coat.way past this ,but only on a scratcht coat is to pva an lots of it,to the point of saturation an then its just the glue holding it together.
 
what does lime do if u add it to your mix. cheers
dont now the chemistry but it livens the mix an makes it more workable,use fresh lime,a month or two old an it will feel dead imo.
 
reason 4 not putting waterproofer in topcoatis it will allow the topcoat to breath,why do you need it?your scratch is waterproof.when it rains the topcoat will suck in the water through to the waterproof scratch then that will push it back to the surface,then runs down the walls and drip drip drip of beads,sun comes out walls dry out and breathing starts again,its the way of keeping our lovely external work fit and well
 
trowel,lime is a natural plasterciser,and in some ways the most underated material within the plastering game.since torment became cheap and readily available in the 30s/40s lots of the majic of lime has been overlooked
 
reason 4 not putting waterproofer in topcoatis it will allow the topcoat to breath,why do you need it?your scratch is waterproof.when it rains the topcoat will suck in the water through to the  waterproof scratch then that will push it back to the surface,then runs down the walls and drip drip drip of beads,sun comes out walls dry out and breathing starts again,its the way of keeping our lovely external work fit and well

Fair comment , i surpose opinions vary just like belly buttons
 
reason 4 not putting waterproofer in topcoatis it will allow the topcoat to breath,why do you need it?your scratch is waterproof.when it rains the topcoat will suck in the water through to the  waterproof scratch then that will push it back to the surface,then runs down the walls and drip drip drip of beads,sun comes out walls dry out and breathing starts again,its the way of keeping our lovely external work fit and well
hows that work then mate?youve just stoped the greatest part of the wall drying with your scratch i wouldnt have thought the top 8 mm would/could dry anything else out but itself!
jmo
 
i dont mean the entire wall, the topcoat breathes.look at it a bit like your skin..moisture need s to go in and out but not to penetrate
 
i dont mean the entire wall, the topcoat breathes.look at it a bit like your skin..moisture need s to go in and out but not to penetrate
but youve just sealed any moisture in with your w/p scratch.
 
sealed what moisture in?the fraction thats gone in when scratching the wall?so if you got two waterproof coats on the walland you get a shrinkage crack wher does the moistur go then?not back out to the face as its waterproof,it will sit in the scratch and travel througt to the brickwork/blockwork wall ties because it cant breathe,why do you think external lime motars with little binder in them(and no waterproofer) lasted so well?why is it that when torment became readily available and the 3to1 brigade got there hands on it you would see walls leaping off?
 
no mate a load of reasons why damp can get in,but as a plasterer just do the best i can to keep my work as good as it can be
 
sorry,didnt mean to get heavy,but this subject cost me about a grand,just wouldnt like to see anyone else bit,appologies dicki
 
one of the lads i work with never heard of putting it in the backing coat always top coat, know he uses it in the backing coat and has never noticed much difference really........
 
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