Rendering. PLEASE HELP

Members online

G2607

New Member
OK first time post so go easy on me..

I have been plastering for about 15 years. I do the occasional rendering job if it's not too big as I work solo. In the last few years I am having constant issues with the top coat of my sand and cement render shrinking, with small hairline cracks.
The mix I am currently doing is:

1st coat
8 Plastering sand
Half bag cement
500ml waterproofer

Top coat
10 plastering sand
Half bag cement
2 shovels hydrated lime.

On existing painted render, thermalite and engineering bricks I do an SBR slurry 2:1 cement to sharp sand. On high suction backgrounds I try and soaking the wall as much as possible. I also use pink Weber mesh on cracked walls.

I understand rendering is not a great idea in certain weather conditions. It's such a shame as I enjoy doing it but very disheartening when a nice job is spoiled by cracks, its got to the point where I'd rather just work indoors! Hopefully someone can tell me where I'm going wrong?

Thanks
 
Gary - 07712182282
ray donovan omg GIF by Sky
 
May I refer you to essex andy's newbie rendering mix guide, if it's still there on the stickies. Should be a mandatory text on courses.
 
Had a look on here but can't seem to find anything. I'm just after a bit of advice. Thought I'd done a fairly decent job. Gutted to see shrinkage but I'm assuming the top coat is drying out too quick
 

Attachments

  • 20231229_152229.jpg
    20231229_152229.jpg
    1.7 MB · Views: 47
  • Screenshot_20240104_213419_WhatsApp.jpg
    Screenshot_20240104_213419_WhatsApp.jpg
    1.2 MB · Views: 46
Don't use mastercrete for external render. A builder I worked for used to get it and had similar problems. It would rub up mint then next day little cracks would appear, drove me nuts. After trying allsorts went to ordinary portland cement and everything went back to normal. Whatever additives they put in it must make it shrink.
 
Funny you should say that as I used rugby cement on a different area and it's absolutely fine. Would never have put 2+2 together though as mastercrete state that their cement is suitable for render. So thanks for that

I'm guessing you're constantly getting 'experts' like me coming on here asking why their render has failed. So apologies for sounding like a broken record
 
Funny you should say that as I used rugby cement on a different area and it's absolutely fine. Would never have put 2+2 together though as mastercrete state that their cement is suitable for render. So thanks for that

I'm guessing you're constantly getting 'experts' like me coming on here asking why their render has failed. So apologies for sounding like a broken record
Glad I could help, every day's a school day.
 
Thanks for all the advice

Potential schoolboy error..
I'm always paranoid about knocking the beads out of plumb/level so I usually put them up after I've done the scratch. But where I have to bring certain beads out I'm potentially increasing the depth for the top coat, thus having to put it on too thick. Would this cause shrinkage?
 
Guttering is covering the very top, hence the screws. Tried using an arch bead but struggled to make it stay put, was a bit springy over such a short distance
 
Don't use mastercrete for external render. A builder I worked for used to get it and had similar problems. It would rub up mint then next day little cracks would appear, drove me nuts. After trying allsorts went to ordinary portland cement and everything went back to normal. Whatever additives they put in it must make it shrink.
We always use ordinary Portland.
 
Glad I could help, every day's a school day.
Massive thank you theshed. Cut out the mastercrete and switched to general purpose. No shrinkage whatsoever. Had no idea about the additives in it so would never have guessed where i was going wrong
 

Attachments

  • 20240328_090727.jpg
    20240328_090727.jpg
    2.8 MB · Views: 35
  • 20240328_091005.jpg
    20240328_091005.jpg
    3.5 MB · Views: 36
Massive thank you theshed. Cut out the mastercrete and switched to general purpose. No shrinkage whatsoever. Had no idea about the additives in it so would never have guessed where i was going wrong
You could always send @theshed some appreciation for his input.
 
20240402_125938.jpg
spoke to soon
This wall took all day to go off so surely can't be drying too quick..
I'm stumped
 
Top