Sand & cement render

[Marshy]

I'm never too old to learn!!!
I've done the sbr slurry over a painted surface but never over thermalites . Always done the same as what I have on this job on thermalites in the past !!

The suction on thermalites is very very high and I know some who are happy to stand with a hosepipe soaking the wall for god knows how long!?? SBR wasn't around when I was serving my time etc so I'm very glad its been around a good while now and as for PVA used on external render work !!??? :rolleyes)

 

[shaky1]

never had aproblem withsand and cemment myself on thermes if your gauges are right.sounds like u got to much feds going in your gauges m8.u got to drown the block work and kill the suction uwont get no cracks then i never have.hppydays p.s why the fcuk are u using pva your aveing a laugh m8

 

[johniosaif]

scud it ..asif....:RpS_unsure:

is that the correct terminology..:RpS_wink:

Well ,yes, but some scud with a paint brush or roller, I scud with a Harling trowel

 

[johniosaif]

The suction on thermalites is very very high and I know some who are happy to stand with a hosepipe soaking the wall for god knows how long!?? SBR wasn't around when I was serving my time etc so I'm very glad its been around a good while now and as for PVA used on external render work !!??? :rolleyes)

Hosing is not the answer ,have to point this out to the greener ones,

 

[Metropolitan Plastering]

never had aproblem withsand and cemment myself on thermes if your gauges are right.sounds like u got to much feds going in your gauges m8.u got to drown the block work and kill the suction uwont get no cracks then i never have.hppydays p.s why the fcuk are u using pva your aveing a laugh m8

Lol it was just a shot in the dark it slows it down inside ,it may have worked it couldn't make it any worse ! I always soak with hose pipe
Feds ??

 

[johniosaif]

I'd have SBR slurried the thermalites before attempting any scratch coat !?

Good here ,where there has been problems before hand but not generally used, we will end up sbr ing plaster board soon.

 

[CTPlastering]

Lol it was just a shot in the dark it slows it down inside ,it may have worked it couldn't make it any worse ! I always soak with hose pipe
Feds ??

It can wen it gets wet and goes tacky again .....

 

[Marshy]

Good here ,where there has been problems before hand but not generally used, we will end up sbr ing plaster board soon.

What you don't do already John!??? :-0

:RpS_laugh:

 

[puddove]

I'd have SBR slurried the thermalites before attempting any scratch coat !?

hi marshy after SBR slurry would you go to the pub to quench your thirst, then scratch coat the next day:RpS_biggrin::RpS_lol:

 

[jesssop]

rend aid then ocr fuk the cost

 

[johniosaif]

4/1 is too strong whether it's worked for yrs or not,
hosing down too much is not recommended , lightly dampen /sprinkle is the way,
if you're hosing down for twenty mins or so join the fire brigade,
I don't think sbr is required on new block work, people are sbr ing everything these days, no one knows why. Waterproof in scratch is fine, the block work is 6/1 strength so you shouldn't apply stronger, night from me. We all live and learn from mistakes,

 

[johniosaif]

What you don't do already John!??? :-0

:RpS_laugh:

No just mix yellow grit ,and blue grit together,,

 

[Marshy]

hi marshy after SBR slurry would you go to the pub to quench your thirst, then scratch coat the next day:RpS_biggrin::RpS_lol:

Have you been watching me Phil !!?? :-0

 

[Marshy]

4/1 is too strong whether it's worked for yrs or not,
hosing down too much is not recommended , lightly dampen /sprinkle is the way,
if you're hosing down for twenty mins or so join the fire brigade,
I don't think sbr is required on new block work, people are sbr ing everything these days, no one knows why. Waterproof in scratch is fine, the block work is 6/1 strength so you shouldn't apply stronger, night from me. We all live and learn from mistakes,

I'm going to bed and going to "SBR" the missus and plan to leave slurry everywhere :-D

 

[jesssop]

heres some proper teck stuff to read
External finishes - Hanson - HeidelbergCement in the United Kingdom

 

[jdplast]

@jdplast where in wigan you from

@wiganlad pem mate, you?

 

[malc]

i would NOT consider rendering on thermalite blocks in sand and cement in the first place!
i would have talked the customer into a full mesh and thincoat , or full mesh and mono.

 

[puddove]

Have you been watching me Phil !!?? :-0

who me ------ just an educated guess, its the first thread I read from you that hasn't mentioned beer :RpS_thumbsup: :RpS_lol: or a pub

 

[jdplast]

Yea we did a flank on the side upto an expansion joint and wet the scratch down without pva and sucked in really quick, so thought I'd try pva it did hold back more without a doubt today with the pva !
What do you mean by curing it ?

curing means to spray a light (and i mean light) spray mist of water onto the surface of the render as it dries. especially important in hot conditions or on high suction backgrounds (like your extra dry scratch coat).

basically the suction of your scratch coat is sucking all the moisture of the top coat too quickly causing it to shrink and crack, you should dampen down the scratch coat (not soak it) then cure it when its finished and maybe the next day too. the curing replaces the moisture being sucked out of it by the backgroud, preventing the shrinkage which causes the cracking.

or summat like that...:RpS_thumbsup:

 

[Dr.B]

Thermalights are pigs to go over especially in the weather we have had recent.
But dampen them down, scratch in a mix that is no stronger than the block itself ie 5:1 and keep it hydrated. (That means getting it on then misting it with the hose to stop it drying too soon not getting it on and getting on the shandy!)
Topcoat 6:1:1 again keep it hydrated. I've spent a day, the day after finishing floating in hot times (summer 95) spraying floated walls.
Nothing wrong with waterproofer in all coats.

 

[lucius]

Something to think about, I was taught 4:1 and was told top coat should be weaker than scratch !

Not on Thermalite

 

[puddove]

heres some proper teck stuff to read
External finishes - Hanson - HeidelbergCement in the United Kingdom

nice 1 Jessop - an interesting read I think you've answered all the questions :RpS_thumbsup: hopefully some of the other guys will take time and read it before spreading

 

[jesssop]

nice 1 Jessop - an interesting read I think you've answered all the questions :RpS_thumbsup: hopefully some of the other guys will take time and read it before spreading

doubt it :RpS_laugh:

 

[Cranny77]

Next time scratch with hpx and mesh it on thermalites

 

[wiganlad]

@wiganlad pem mate, you?

Live facing hienze pal drink in pem. Lee jones

 

[johniosaif]

They're talking wiganese, anyone know it

 

[Fatarm]

Its a code i think??

 

[plasterjfe]

They're talking wiganese, anyone know it

I happen to be fluent many north western dialect j.

They live and drink in pem - pemberton. A suburb of Wigan.

They don't know it but I bet they shared a few taxis home pi55ed before

 

[church]

theres a clue in the fact that the dashing came off easy ffs , at least you wont have to much trouble getting the render off and doing it again . Theres so much info out there like the link jessop posted , yet people still fook it up :RpS_confused: amazing .

 

[wiganlad]

I happen to be fluent many north western dialect j.

They live and drink in pem - pemberton. A suburb of Wigan.

They don't know it but I bet they shared a few taxis home pi55ed before

Thas reet lad is.

 

[essexandy]

your main problem was that after a couple of weeks the scratch coat was dry as fook and sucking like a .....well fill in the blank yourself.

The pva wont do much you needed to wet the scratch coat down and possibly could have done with curing it during drying

I've left scratch coats for weeks on a number of occasions with suffering from excessive suction, it's all about getting the scratch coat to cure properly in the first place.

Right, I know there are loads of posts about render and cracks but this job is doing my nut in!!
We hacked off an old dash as it was blown and had no scratch we literally peeled it off no hassle..
We scratched over the thermalites with a 4:1 mix with plenty of water proofer. Left it a couple of weeks then started top coating using 5:1:1 with waterproofer/retarder .
Today we even unibonded over the scratch before top coating it all went well ruled off rubbed up sweet but then cracks appear everywhere, I don't have an answer for the customer it's so frustrating , can anyone help ???

Yea we did a flank on the side upto an expansion joint and wet the scratch down without pva and sucked in really quick, so thought I'd try pva it did hold back more without a doubt today with the pva !
What do you mean by curing it ?

If I can't work today due to my sides hurting you'll be getting an invoice:RpS_wink:

:RpS_lol:

Good here isn't it.

Everyone has had
problems,they rest are liars

Not necessarily @johniosaif, not if you listen and learn from those with past experience.

Hosing is not the answer ,have to point this out to the greener ones,

I'd disagree John. I almost always hose down aircrete blocks, not to the point of stopping any suction but lessening it. The water absorbed into the blocks will also slowly come back out through the scratch coat helping it to cure nice and slowly, meaning I don't have to go back as often to keep the scratch hydrated.

theres a clue in the fact that the dashing came off easy ffs , at least you wont have to much trouble getting the render off and doing it again . Theres so much info out there like the link jessop posted , yet people still fook it up :RpS_confused: amazing .

I'm only surprised that you're surprised mate:RpS_biggrin:

 

[theclemo]

I don't think this is a plasterers forum it's a chancer forum.

 

[irish_spread]

There is no absolutely 'correct' rendering mix, it's all down a mix of variables such as brick/block type, temperature, direct sunlight, proximity to sea, traffic vibration, coarseness of sand etc. It takes years of experience to determine which mix is best suited to each job, not necessarily what the block manufacturers dictate.

There are, however, completely wrong ways of rendering and no course will be able to educate these skimmers :RpS_thumbup:

 

[johniosaif]

I've left scratch coats for weeks on a number of occasions with suffering from excessive suction, it's all about getting the scratch coat to cure properly in the first place.





If I can't work today due to my sides hurting you'll be getting an invoice:RpS_wink:



Good here isn't it.



Not necessarily @johniosaif, not if you listen and learn from those with past experience.



I'd disagree John. I almost always hose down aircrete blocks, not to the point of stopping any suction but lessening it. The water absorbed into the blocks will also slowly come back out through the scratch coat helping it to cure nice and slowly, meaning I don't have to go back as often to keep the scratch hydrated.



I'm only surprised that you're surprised mate:RpS_biggrin:

For hosing, I mean soaking it for ages, , I dont think its like old brick work which absorbs ,as Irish says,lots of factors and we decide on the day using common sense and past experience and google of course...

 

[johniosaif]

Hosing is not the answer ,have to point this out to the greener ones,

See here, where the Essex lads get it wrong or perhaps I should of said excessive hosing,it's not recommended to hose down ,just a sprinkle but we all do to an extent..