New render veins appearing

Members online

Total: 440 (members: 2, guests: 438)

Share this page

K

kw38

New Member
Hope someone can help
I have scratch coated wall using 3:1
1 sharp,2buiding sand: 1 cement with waterproofer . Left it cure for 1 and half weeks, wet scratch prior to top coating , waited for water to soak in so just damp and still suction then top coated using 6:1:1 , 3 sharp Sand, 3 building sand:1 cement: 1 lime no waterproofer and cement used is opc
And wetted down for 3 days after to help curing
About week and half later I'm getting veins showing when soaked and drying out. Will this lead to cracks like I think it will
I've only top coated a 1 m2 patch as I know the problems everyone has been getting with render on here
Any professional input would be much appreciated
 
Last edited:
For rendering I use a 5:1:1 mix or 4:1:1 is fine. A 3:1 is quite strong and a 6:1 quite week I use waterproof or Feb admix in both scratch and top coat
 
I forgot to add that it's had 2 scratch coats as the wall was pretty uneven, first 3:1 and second 4:1 with relevant curing times in between so 6:1:1 should of been fine and it didnt dry out too quick either
 
No not this time, i did the first patch, i used a 6:1:1 with waterproofer and it crazed , then i tried patch 2 without waterproofer as it states on back of waterproofer tub " do not use with lime based mixes" which is pretty vague. does this mean lime putty, hydraulic lime, or lime in general, very vague. So i tried the same mix ratio without the waterproofer, but still crazed which is highlighted when wetting down the next day.
 
and also lime is a natural plasticiser. so dint add any instead of waterproofer as the problem may have been over plasticising
 
Not at all
Appreciate all feedback but I really think it's the sand we 're getting in South Wales is not well graded enough. We're getting all the dredged s**t.
I'm gonna try some pit sand that Travis can get in from up north. See how that works out. I tried a 5:1:1 with waterproofer but still crazed. So I have been listening. Really think it's sand
 
kw38 said:
Not at all
Appreciate all feedback but I really think it's the sand we 're getting in South Wales is not well graded enough. We're getting all the dredged s**t.
I'm gonna try some pit sand that Travis can get in from up north. See how that works out. I tried a 5:1:1 with waterproofer but still crazed. So I have been listening. Really think it's sand
Click to expand...
Definitely worth a try changing sand, few years ago I was using a dodgy batch of silver sand and I was getting small hairline cracks as soon as I changed to yellow 50/50 it was fine. Trial and error sometimes.
 
Yea I think it is . I have Bern plastering rendering for over 20 years and never had this problem before. It's been frying my brain to be honest. Have been doing mostly internal work for last year and I come to this and am really disappointed with this happening
 
I always put a dash of waterproofer in even when using lime only for top coat and when I mean a dash I mean gob ful never had a come back and never had a craze touch wood I use 4-1 top and 5-1-1 top have done a 6-1-1 as well and worked well
 
Pagey said:
I always put a dash of waterproofer in even when using lime only for top coat and when I mean a dash I mean gob ful never had a come back and never had a craze touch wood I use 4-1 top and 5-1-1 top have done a 6-1-1 as well and worked well
Click to expand...
What sand do you use?
 
Normal render sand although it's become a chore getting decent sand if it's not that great I will put a bit of building in it had some great sand lately though nice yellow colour and nice to rub up,down here we get a lot of Leighton buzzard but I'm not a fan seems to hold water to much I prefer the westerham myself if I can get hold of it took me a while to do my mix that I felt suited me,I've only ever used sharp sand on restoration work as a scratch coat myself them boys who do that work are on a different level rule off last min and rub up as they go hard to get used to that as a plasterer I would get on then rule off these blokes would put a panel on then go have a tea break then come back and rule it off always came out perfect though
 
Pagey said:
I always put a dash of waterproofer in even when using lime only for top coat and when I mean a dash I mean gob ful never had a come back and never had a craze touch wood I use 4-1 top and 5-1-1 top have done a 6-1-1 as well and worked well
Click to expand...
what part of the country you from as different places have different sand
 
Pagey said:
Normal render sand although it's become a chore getting decent sand if it's not that great I will put a bit of building in it had some great sand lately though nice yellow colour and nice to rub up,down here we get a lot of Leighton buzzard but I'm not a fan seems to hold water to much I prefer the westerham myself if I can get hold of it took me a while to do my mix that I felt suited me,I've only ever used sharp sand on restoration work as a scratch coat myself them boys who do that work are on a different level rule off last min and rub up as they go hard to get used to that as a plasterer I would get on then rule off these blokes would put a panel on then go have a tea break then come back and rule it off always came out perfect though
Click to expand...
That yellow sand your on about, is it pit sand?? ive just got some of that in, really fine, mixes up really nice and creamy and gives a really fine finish if its the same stuff. and this stuff holds the water better too which shows its well graded, the building sand the water used to come to top of the mix within 5 minutes and the bottom of mix was left dry. lets hope this works anyway
th
 
kw38 said:
That yellow sand your on about, is it pit sand?? ive just got some of that in, really fine, mixes up really nice and creamy and gives a really fine finish if its the same stuff. and this stuff holds the water better too which shows its well graded, the building sand the water used to come to top of the mix within 5 minutes and the bottom of mix was left dry. lets hope this works anyway
th
Click to expand...
Last couple of Ton we got came from local merchants and was pukka but feel more luck than judgement the sand that water separated from drives me mad and defo dried grey once finished that was from travis Perkins
 
We only ever use a half shovel of lime to 15 sand and 3 cement with about 100ml of waterproofer+plasticiser(2in1). Don't like using too much lime from late April to late September. Most of the time we go 4-1 scratch coat with plasticiser. We seem to get a better soaking of the scratch coat and holds damp better when finishing. We find when wetting down a scratch coat with waterproofer the water is just running off it and not soaking in fully.
 
solway said:
We only ever use a half shovel of lime to 15 sand and 3 cement with about 100ml of waterproofer+plasticiser(2in1). Don't like using too much lime from late April to late September. Most of the time we go 4-1 scratch coat with plasticiser. We seem to get a better soaking of the scratch coat and holds damp better when finishing. We find when wetting down a scratch coat with waterproofer the water is just running off it and not soaking in fully.
Click to expand...
do u use that much water proofer in scratch coat, see i find that too much
 
The Travis plastering sand is exactly the same grade as their building sand. And the only plastering sand we can get here is wickes or b& q but I done a silt test on both and both 20-25% silt . So shite
 
kw38 said:
The Travis plastering sand is exactly the same grade as their building sand. And the only plastering sand we can get here is wickes or b& q but I done a silt test on both and both 20-25% silt . So shite
Click to expand...

their plastering sand is bright orange... never seen sand like it :D
 
actually trying the wickes plastering sand now. it is better than i thought. its well graded and alot cleaner than i thought.
Its the b & q diall sand thats crap, way to much silt in that s**t.
 
I just wanna say i have found the problem after many test patches
Its the lime
My last test patch ( top coat)consisted of 5:1, s:c 3 x 5 litre caps of freeflow w/p using wickes plastering sand and no lime. and after 3 weeks still no crazing,
It must be the lime ive tried everything else
Even using the exact mix using plastering sand with lime it cracked so its gotto be the lime
But i will keep on using the plastering sand as it is much better graded
Thanks for all your imput guys
Keith
 
You must log in or register to reply here.
Top