Rendering. PLEASE HELP

[G2607]

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

 

[Stevieo]

Theres your problem right there.

What's your number pal?

 

[G2607]

Gary - 07712182282

 

[Dollar]

 

[themucky1]

Gary - 07712182282

 

[zombie]

Ffs

 

[Brimstone]

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.

 

[G2607]

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

 

[theshed]

Are you using mastercrete cement?

 

[G2607]

I use whatever is on the shelf, but yes normally blue circle

 

[theshed]

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.

 

[G2607]

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

 

[Stevieo]

8

 

[theshed]

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.

 

[Dollar]

Glad I could help, every day's a school day.

Go to bed

 

[Stewie03]

Would of looked nice if them sills were rendered aswell would look sharp

 

[G2607]

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?

 

[bobski]

View attachment 769508

I cant help but read that in an I n d ian accent.





Or Chinese.

 

[themucky1]

Would of looked nice if them sills were rendered aswell would look sharp

Would’ve looked nice had the bead gone right up to the roofline and used an arch bead on that window head but wtf do I know

 

[G2607]

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

 

[G2607]

View attachment 76956
Would’ve looked nice had the bead gone right up to the roofline and used an arch bead on that window head but wtf do I know

But I do take your point

 

[Shovel120]

Looks like bad sand. Was it plastering sand.

 

[G2607]

Yes mate only use plastering (think the top coat was mainly wickes)

 

[Shovel120]

Hard to get a clean sharp plastering sand. We cut bac in the lime when sand is poor

 

[Stevieo]

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.

No ot shouldn't

 

[Stewie03]

View attachment 76956
Would’ve looked nice had the bead gone right up to the roofline and used an arch bead on that window head but wtf do I know

It will settle m8

 

[essexandy]

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.

 

[Spitandpolish]

We always use ordinary Portland.

Shut up

 

[Stevieo]

We always use ordinary Portland.

No you don't

 

[Spitandpolish]

No you don't

Does he f**k.

 

[G2607]

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

 

[Cockney]

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.

 

[Monkey Boy]

You could always send @theshed some appreciation for his input.

Someone coming back with a just thanks is a rare good start

 

[essexandy]

Someone coming back with a just thanks is a rare good start

Thank you for that.

 

[G2607]

spoke to soon
This wall took all day to go off so surely can't be drying too quick..
I'm stumped