Rendering celcon blocks

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What happens when the door slams? doube skin brick work, tied, strapped, weighted by the roof timbers, tied to the joists.....what happens?
House will fall down most likely.

Best thing to do is get paid cash and change your number as soon as you do.

That way if it's still up when you shut the gate, the jobs a good un

#90sbuilderboomtownpartydays
 
Evening all,

I have asingle story building with celcon blocks that I need to render. I’m thinking my options are either making a brush on slurry of sbr, sand, cement, water, wait to dry then scratch coat as normal.

Or would galvanised steel mesh be a better option?

or am I well out and someone here has done a few of these and found something that works? Ratios would be great.
Thanks.

ps, the building has had an alteration after completion hence the odd block work to the left of the door. Not looking for comments on this. Thanks again.
I would give it a slurry coat with sbr. Leave it dry. Scratch coat. Top coat. Job done. I'm with you on the block work who gives a s**t what it looks like when its going to be plastered . Like a school playground with some of the replies you've had, just lads showing off acting like they know it all instead of actually helping out
 
House will fall down most likely.

Best thing to do is get paid cash and change your number as soon as you do.

That way if it's still up when you shut the gate, the jobs a good un

#90sbuilderboomtownpartydays
If that wall fell down nothing would happen as it had no load bearing to the roof so what you’re saying doesn’t make any sense. Stick to skimming plasterboards.
 
I would give it a slurry coat with sbr. Leave it dry. Scratch coat. Top coat. Job done. I'm with you on the block work who gives a s**t what it looks like when its going to be plastered . Like a school playground with some of the replies you've had, just lads showing off acting like they know it all instead of actually helping out
Hi, thanks for a normal reply! Yeh unfortunately for me that’s what I thought I’d do before I thought about asking the question on here...should have stuck to my guns and trusted myself.
thanks again, really appreciate the answer.
 
I would give it a slurry coat with sbr. Leave it dry. Scratch coat. Top coat. Job done. I'm with you on the block work who gives a s**t what it looks like when its going to be plastered . Like a school playground with some of the replies you've had, just lads showing off acting like they know it all instead of actually helping out
Slurry coat and “Leave it dry”
Stupid boy, go to bed!!!
 
I would give it a slurry coat with sbr. Leave it dry. Scratch coat. Top coat. Job done. I'm with you on the block work who gives a s**t what it looks like when its going to be plastered . Like a school playground with some of the replies you've had, just lads showing off acting like they know it all instead of actually helping out
Point is a man who does blockwork like that and hacks plastic to bits with what I can only imagine was a bread knife isn't going to then get render looking spot on. As that would require pride in one's work. Classic bodged self build, that I see customers do from time to time
 
I would give it a slurry coat with sbr. Leave it dry. Scratch coat. Top coat. Job done. I'm with you on the block work who gives a s**t what it looks like when its going to be plastered . Like a school playground with some of the replies you've had, just lads showing off acting like they know it all instead of actually helping out
Yeh the blockwork isn’t great. I could have done better but I know it’s being rendered so just made sure it was level etc.
Point is a man who does blockwork like that and hacks plastic to bits with what I can only imagine was a bread knife isn't going to then get render looking spot on. As that would require pride in one's work. Classic bodged self build, that I see customers do from time to time
the cladding is having edging cap on the ends so you won’t see it. Get a piece and try and cut it long ways. The blockwork is being rendered....why does it matter if it looks 100 percent....it doesn’t, it’s level and plumb and that’s what counts. The render will look fine don’t worry
 
Have you used rendergrip on celcon blocks before?

If its sand and cement you are using then Rendagrip will work a treat. It will kill most of the suction but not all which is good for a bit of grab but still manageable. Apply it the day before it has to be dry.
 
If its sand and cement you are using then Rendagrip will work a treat. It will kill most of the suction but not all which is good for a bit of grab but still manageable. Apply it the day before it has to be dry.

think it’s going to be the safest way. Haven’t used it before though. Does it just paint on? Is it messy like blue grit
 
think it’s going to be the safest way. Haven’t used it before though. Does it just paint on? Is it messy like blue grit
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Yes paint it on and you can add 5% water. It jelly like so not bad to use but if it gets into woodgrain plastic and dries you are done for. Cover up well.
 
If you spent a bit more time on here you'd know that the answerers really do know their stuff but have higher standards than most site monkeys. They therefore get a bit offended when they see poor workmanship, and advise the poster accordingly. If they call it crap then it probably is crap, and accept the piss take and learn.

You've actually had a lot of advice, but don't want to try something new and learn from it, when it's your own job and relatively low risk/low cost. I'd jump at the chance myself.

It probably won't fall down unless the mortar mix was too weak or too dry, or conversely too strong, but it is almost guaranteed to crack, and badly. You've built in a huge, thick mortar joint over 4 or more courses, no amount of metal is going to stop cracking. When I was a heavily over qualified and experienced site QS I would have failed it and refused to pay you.
I'm not going to give you advice on rendering beyond that, others far better have already done that.
 
If you spent a bit more time on here you'd know that the answerers really do know their stuff but have higher standards than most site monkeys. They therefore get a bit offended when they see poor workmanship, and advise the poster accordingly. If they call it crap then it probably is crap, and accept the piss take and learn.

You've actually had a lot of advice, but don't want to try something new and learn from it, when it's your own job and relatively low risk/low cost. I'd jump at the chance myself.

It probably won't fall down unless the mortar mix was too weak or too dry, or conversely too strong, but it is almost guaranteed to crack, and badly. You've built in a huge, thick mortar joint over 4 or more courses, no amount of metal is going to stop cracking. When I was a heavily over qualified and experienced site QS I would have failed it and refused to pay you.
I'm not going to give you advice on rendering beyond that, others far better have already done that.

I used larger mortar joints and a wetter 5-1 mortar mix as advised by h+h. I know these blocks are prone to cracking though but the building has actually been like this for 2 years now. Only had one crack underneath the front windowsill whichI’m no surprised about as this wall is taking the load of the roof on the lintel. The side walls aren’t taking any weight and have had no cracks at all.
I have a feeling the render may crack but hopefully the lime in the mix will help.

I have explained this many times but the block work wasn’t crucial from a beauty aspect as it was being rendered.
 
I used larger mortar joints and a wetter 5-1 mortar mix as advised by h+h. I know these blocks are prone to cracking though but the building has actually been like this for 2 years now. Only had one crack underneath the front windowsill whichI’m no surprised about as this wall is taking the load of the roof on the lintel. The side walls aren’t taking any weight and have had no cracks at all.
I have a feeling the render may crack but hopefully the lime in the mix will help.

I have explained this many times but the block work wasn’t crucial from a beauty aspect as it was being rendered.
I still don't understand that if you knew it was going to be rendered why you would chose to build out of celcon and not a concrete block ,knowing full well the problems that may occur when rendering over a poor unsuitable material. Celcon blocks should only be used internally when dry lining is the plastering method chosen. Only builders with limited or no experience of wet plastering use this type of block because they love the fact they are easy and light to lay . Never a thought for the problems the plasterer will have and the effect of excessive suction on a gypsum based plaster or sand and cement render. Its just making a straight forward job over complicated.
 
I still don't understand that if you knew it was going to be rendered why you would chose to build out of celcon and not a concrete block ,knowing full well the problems that may occur when rendering over a poor unsuitable material. Celcon blocks should only be used internally when dry lining is the plastering method chosen. Only builders with limited or no experience of wet plastering use this type of block because they love the fact they are easy and light to lay . Never a thought for the problems the plasterer will have and the effect of excessive suction on a gypsum based plaster or sand and cement render. Its just making a straight forward job over complicated.
For internal solid plastering I'd rather work over Celcon blocks than anything else.
 
whys that Andy?
Because if you get a decent suction from the substrate you'll get less suction when skimming. Same as with external rendering.
Plus I just like getting a wall on and not having to wait to long before scratching up.
I always use screeds though and I know that those who free rule prefer low suction backgrounds.
 
Which bizarre reinforcement are you talking about? Galvanised straps being used for their purpose?
Over the years I’ve seen plenty of doorways blocked or bricked up without being tied in the way you suggest.
you answered my question about why would it fall down by saying because it’s a bodge.
so I’m asking structurally how it would fall down.....is this another question you don’t have the brains to answer :)
You may have seen it done a fair few times but rendered or not you have created a straight joint which will crack so you either need to make it an expansion joint or the better idea press the plastic mesh into your scratch coat. It’s hard to say what mix to use in all fairness if you use the proper gauge for the scratch coat it will be to strong for the blocks and could fail ie drop off the wall later on as @Tom81 said your next coat after the scratch should be thinner and that may be a problem if your block work isn’t straight, you may need more than one scratch coat to bring it out to level
 
I still don't understand that if you knew it was going to be rendered why you would chose to build out of celcon and not a concrete block ,knowing full well the problems that may occur when rendering over a poor unsuitable material. Celcon blocks should only be used internally when dry lining is the plastering method chosen. Only builders with limited or no experience of wet plastering use this type of block because they love the fact they are easy and light to lay . Never a thought for the problems the plasterer will have and the effect of excessive suction on a gypsum based plaster or sand and cement render. Its just making a straight forward job over complicated.

well I’m not a builder, and yes they are easier to lay. Also better thermal qualities. Tbf there’s been a few solutions here about rendering celcons so I’m sure it’s not that big of a deal.
 
You may have seen it done a fair few times but rendered or not you have created a straight joint which will crack so you either need to make it an expansion joint or the better idea press the plastic mesh into your scratch coat. It’s hard to say what mix to use in all fairness if you use the proper gauge for the scratch coat it will be to strong for the blocks and could fail ie drop off the wall later on as @Tom81 said your next coat after the scratch should be thinner and that may be a problem if your block work isn’t straight, you may need more than one scratch coat to bring it out to level

thanks, the blockwork is straight and level it just doesn’t look great (knowing I was rendering it)
Yes the joint will have eml over it.
 
All render systems reinforced meshed whatever you want will not hold back structural cracks when it's applied directly onto substrate,
the mesh reinforced systems are just to prevent the render failing not the substrate,
 
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