2nd render coat not stuck

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Ed30ste

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Hi please go easy i am new to cement rendering. I've got a 6.6m by 1.5m block wall i used a 4-1 plastering sand/cement mix on the scratch coat then 5-1 coat. The scratch coat has stuck solid but my top coat cam away in parts so i have removed it all. Not sure what to do next. Thanks for any advice
I would of paid a professional but out of the 3 i contacted only one turned up but then failed to even call back.
 

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Hi please go easy i am new to cement rendering. I've got a 6.6m by 1.5m block wall i used a 4-1 plastering sand/cement mix on the scratch coat then 5-1 coat. The scratch coat has stuck solid but my top coat cam away in parts so i have removed it all. Not sure what to do next. Thanks for any advice
I would of paid a professional but out of the 3 i contacted only one turned up but then failed to even call back.
Was your topcoat thicker than your scratch coat
 
First up. That don't look 4 - 1.


Secondly, your supposed to scratch for a key, not for looks. There is no depth in the scratches - and for me not regular enough.

Also my base for traditional topcoat is always rough, not uneven but rough for final coat to lock onto. The perfect key would be like a tyrolean or pebble dash where your coat would mechanically lock on.

Yours is flat and bald.

I'd slurry that to coat over.
 
First up. That don't look 4 - 1.


Secondly, your supposed to scratch for a key, not for looks. There is no depth in the scratches - and for me not regular enough.

Also my base for traditional topcoat is always rough, not uneven but rough for final coat to lock onto. The perfect key would be like a tyrolean or pebble dash where your coat would mechanically lock on.

Yours is flat and bald.

I'd slurry that to coat over.
Thanks for the reply. I measured it out in buckets and it is definitely 4-1. Should I continue or try and get someone in to sort it out as I don't want to do it all again for it to fail.
 
First up. That don't look 4 - 1.


Secondly, your supposed to scratch for a key, not for looks. There is no depth in the scratches - and for me not regular enough.

Also my base for traditional topcoat is always rough, not uneven but rough for final coat to lock onto. The perfect key would be like a tyrolean or pebble dash where your coat would mechanically lock on.

Yours is flat and bald.

I'd slurry that to coat over.

I thought same but as I'm not a renderer, I kept me gob shut.

I've just bought a new scratch comb actually. The tines are flat. The fuckign thing is lethal if you don't pull the scratchcoat off the wall with it, if leaves one helluva key.
 
There are quite a few mistakes you could have made . Was the second coat plastering sand? Why feb and waterproofer? Most liquid waterproofers have a plasticiser already in so may have been over plastercised. Over mixing would also have killed the mix. That scratch although in waves doesn’t look deep enough.

Also did you put waterproofer in the scratch coat then wet it down well? You could have had a film of water between the two coats. A light damping with no surface water is sufficient. Also how wet was it when you rubbed it up? Of you was too late you could have caused separation by rubbing up too late and too hard.
 
You also look like you’ve troweled over your scratch to make it look all pretty, problem is that this closes the face in (seals it), your better to rule off flat and leave the face open and just key it.
Is that a bellcast on a garden wall?
 
There are quite a few mistakes you could have made . Was the second coat plastering sand? Why feb and waterproofer? Most liquid waterproofers have a plasticiser already in so may have been over plastercised. Over mixing would also have killed the mix. That scratch although in waves doesn’t look deep enough.

Also did you put waterproofer in the scratch coat then wet it down well? You could have had a film of water between the two coats. A light damping with no surface water is sufficient. Also how wet was it when you rubbed it up? Of you was too late you could have caused separation by rubbing up too late and too hard.
Hi thanks for your reply. Yes the 2nd coat was the same materials just 5-1. I used feb and wp because that's what I read on the net before I started. Not sure if I over mixed it or not I don't think I did but I am a total novice as you can see. I agree with the scratch its crap. I did put wp in the scratch and dampened it before top coat with a small hand pump sprayer. The rubbing was quite hard to do and I do think that's some of the problem also it was quite a hot day.
What should I do next in your opinion I am thick skinned and know ive dropped a bollock : (
 
You also look like you’ve troweled over your scratch to make it look all pretty, problem is that this closes the face in (seals it), your better to rule off flat and leave the face open and just key it.
Is that a bellcast on a garden wall?
Hi thanks for your reply. Yeh its very flat and quite smooth :muyenojado: I put the bead on to try and guide me for the depth with wood on top of the wall with the depth set. I only tried to do it because I couldn't find a plasterer who was interested in the job and I am just trying to get the garden something like before the winter. Ive done bits of plastering in the house and done a very nice job so I thought how much different can it be :endesacuerdo:.
Now I know.....
 
Hi please go easy i am new to cement rendering. I've got a 6.6m by 1.5m block wall i used a 4-1 plastering sand/cement mix on the scratch coat then 5-1 coat. The scratch coat has stuck solid but my top coat cam away in parts so i have removed it all. Not sure what to do next. Thanks for any advice
I would of paid a professional but out of the 3 i contacted only one turned up but then failed to even call back.
This picture after the top coat was taken off ?
 
I'd say that you went wrong by wanting it done to cheaply. I can't see any reason why a spread would turn down such a nice simple little job if they were getting the correct money for it.
Not your correct, their correct.
Out of interest how soon did you put the top coat on after the scratch? One, maybe two days?
 
I'd say that you went wrong by wanting it done to cheaply. I can't see any reason why a spread would turn down such a nice simple little job if they were getting the correct money for it.
Not your correct, their correct.
Out of interest how soon did you put the top coat on after the scratch? One, maybe two days?
Hi i contacted 3 different plasterers 2 never even turned up and the one who did looked at it and said he would call me with a price and never did, so no i never expected it done cheaply. 2nd coat was about a week after because of weather.
 
Hi i contacted 3 different plasterers 2 never even turned up and the one who did looked at it and said he would call me with a price and never did, so no i never expected it done cheaply. 2nd coat was about a week after because of weather.
Should of contacted 3 more then tbh. Most tradesman are s**t and never get back to you. Was always a mission trying to find someone for my own house, now luckily I know good people in every trade though
 
Get it back to flat scratch coat with no bumps. Ordinary pva is no good but Wickes sells waterproof pva that will work. Look at the directions on the label but give it a primer coat and let dry then a tack coat and render over when it starts to go from wet to tacky but not dry.

Dont use feb and wp it will be over plasticiced use one or the other. Better still try and use Weber ocr or Johnstones one coat render. You only need to add water nothing else. Being on pva you might find it wants to slide down so wait for the pva to go tacky, get it on and dont play with it or it will either slide or slump crack so get it on and wait for it to stiffen up naturally before you play with it. Pick a dry day but not sunny or above 20c but above 15c.

Dont let it go dry or you will be back to it failing again. The bagged ocr will be easier than hand mixed sand and cement.
 
I do alot of sand and cement work both externally and internally for damp work.
It looks like a number of things are the issue.
Your scratch coat looks like it was trowelled up then scratched a big no no, also its not scratched up enough( any flat spot not keyed wil just hang and fall off.). If youve got it back to the scratch now use an angle grinder to (gently) create a better key. then go for your top coat(do not use pva) the waterproofer in your original scratch acts as a retarder if you pva it, it wont bond properly. Use your grinder to make your scratch look more like this.
 

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I am going to go at it with the grinder for sure. When i did the 2nd coat it was very hot high 20s. when i went to rough it up it had dried and i got a full bag of material on the floor after scratching. I have lost quite a bit of confidence after this but i will give it another shot before i take the lot of and pursue a plasterer to do it. Its not about saving money i would of paid in the first place but couldn't get anyone to do it. Anymore tips before i go at it?
Thanks for all the help its really appreciated.
 
I am going to go at it with the grinder for sure. When i did the 2nd coat it was very hot high 20s. when i went to rough it up it had dried and i got a full bag of material on the floor after scratching. I have lost quite a bit of confidence after this but i will give it another shot before i take the lot of and pursue a plasterer to do it. Its not about saving money i would of paid in the first place but couldn't get anyone to do it. Anymore tips before i go at it?
Thanks for all the help its really appreciated.
The key in your base coat is not the reason why it’s failed !
I think the base was dry and the hot weather dried out your next coat and that’s the reason

Try some methods in small areas to get it right mate
 
OK so today I got the grinder on it its not the neatest but my arms where like jelly. Before I attempt it is there anyone near Shaw oldham who fancy the job. I've got all the materiasl and a cement mixer I can also labour for you if needed. Cheers ste
 

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OK so today I got the grinder on it its not the neatest but my arms where like jelly. Before I attempt it is there anyone near Shaw oldham who fancy the job. I've got all the materiasl and a cement mixer I can also labour for you if needed. Cheers ste
Sbr the wall and go again
 
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