render over stainless steel mesh hairline cracking

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valboy

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Hi guys, hope you can help. I've just insulated externally the top half of my house as it's single skin which used to have tiles on the front of it. I used the suitable insulation and fixed the stainless steel mesh over the top of it over lapping it by 100mm, the mesh in question is deep ribbed. Mix's applied are 3/1 scratch with freeflo in it and 4/1 top coat with freeflo and lime in, it's been 3 days and there are hairline cracks appearing where the lines of the mesh are. The render has gone off lovely and solid it's just these b*****d cracks. I left the scratch coat a week before the top coat went on so I'm a little baffeled. Thanks.
 
It was recommended to me at the building suppliers, I don't do a lot of rendering myself so reaserched as much as I could, got a really good finish except for these bloody cracks. It was a warm day but kept it nice and wet through out and into the evening and next day. It was kingspan with like a fibre skin on it not foil back. I did question weather 3/1 was a bit strong but was do paranoid about it falling off I thought to make it nice and strong. Could this cause the cracks? I will get some pics up for you to see.
 
 
Kingspan K3-5-8-18...... Which one did you use? I though it was funny when someone came on here with the idea EWI with s&c . Never thought that's possible ! I am really keen to see these pics. Also , how long did you wait before the top coat? Was the mesh tidy where the joints are ? And how did you fix the mesh to the insulation?
 
Not sure how to post pics up lads, so do you think k rend would have been better?. I left it a week before top coat went on, there where no cracks in the scratch coat either so I assumed all was ok. The mesh was very tidy, overlapping all joints by 100mm. I thought waterproofer stopped a lot of the water getting in but not all of it.
 
Also the bottom of the house is a cavity wall so didn't need insulating and I did that at the Sam time and its great, no cracks hollow patches nothing, gone off lovely.
 
Is
Rigsby said:
The insulation will have absorbed the heat. If you used freeflo then watering down would have been pointless, it is waterproof. Too strong a mix and rapid drying.

Should have used a polymer modified render. Let it dry out and skim over with something like Weber Lac with Weber mesh embedded
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This similar to k-rend hpx? Or is it a finish coat. Thanks
 
If it's ribbed lath maybe towards the ribs it's a bit thin having only two coats which are strong btw sounds like it could of expanded in these parts with the heat maybe hard to know without seeing it really
 
Not sure if someone has given you a spec for that but if so then that sounds very wrong to me.
A sand and cement render must never be stronger than than the previous coat and def never stronger than the substrate.
In this case it sounds way way to strong.
I usually mix approx a 5/6-1 scratch and then 6/7-1 Top.
May not sound strong but bricke's muck is about 5/6-1.
So if that's used for block work then Imagine what it needs to be for EWI.
In my opinion I would never use sand & cement over EWI any way.
Was the insulation fixed to a dodgy surface?
 
Really don't know how to get pics up lads and I've got loads of the whole process.all the products came recommended by the manager of the building suppliers. The surface beneath was sound, concrete blocks.
 
Hope these help, and thanks for all the input
 

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That's ridiculous ! Whoever recommended the products and method statement is an idiot! You shouldn't do it in a first place! I tried to zoom the picture with the mesh and boards, but can't see the details! You didn't told us what kingspan did you use? Was it k5? It looks more like brick slip wall to me, but as I said, I can't zoom in to see it.The cracks are most likely caused by the boards and mesh, not the render ratio .One more think, the mesh is faaaaaar at the back of the render,by the look of it, which pretty much eliminates the effect.
 
By the way thanks for the pics , now I know there are very brave and sharp minds in this industry . I thought I will never see it - EWI with sand and cement, but hey ho, now I am waiting to see the next c**t who will do EWI+ s&c + tiles:risas:.Just wondering how long until we see the pics on here:maraca:
 
vfr12 said:
By the way thanks for the pics , now I know there are very brave and sharp minds in this industry . I thought I will never see it - EWI with sand and cement, but hey ho, now I am waiting to see the next c**t who will do EWI+ s&c + tiles:risas:.Just wondering how long until we see the pics on here:maraca:
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We live and learn Vfr12, fair does to the op, he has asked for help and clearly said he knows little of rendering. I would be blaming the building supply company as it was them that gave him the spec.

Yes maybe if he had a mesh embedded in the S&C that may have helped but sand and cement on insulation is a no brainer.

Maybe suggestions on how to rectify will be of help. Mine is Weber Lac with mesh and a acrylic finish like Weber.plast TF150 that will have some stretch to it. Better still Santane if finances allow. Even High Build will have some give.
 
Rigsby said:
We live and learn Vfr12, fair does to the op, he has asked for help and clearly said he knows little of rendering. I would be blaming the building supply company as it was them that gave him the spec.

Yes maybe if he had a mesh embedded in the S&C that may have helped but sand and cement on insulation is a no brainer.

Maybe suggestions on how to rectify will be of help. Mine is Weber Lac with mesh and a acrylic finish like Weber.plast TF150 that will have some stretch to it. Better still Santane if finances allow. Even High Build will have some give.
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Yes, Rigsby I do agree with you! I am not perfect either!The post you was quoting is part of the first one. Never intended to critic the op for following the spec. I do follow the spec every time and if I don't like something I do make sure the man above knows . And if he says it's ok , than its ok. I was aiming at the manager , who gave him the spec, not the op if that makes sense. Apologies if it felt the other way around!
 
vfr12 said:
Yes, Rigsby I do agree with you! I am not perfect either!The post you was quoting is part of the first one. Never intended to critic the op for following the spec. I do follow the spec every time and if I don't like something I do make sure the man above knows . And if he says it's ok , than its ok. I was aiming at the manager , who gave him the spec, not the op if that makes sense. Apologies if it felt the other way around!
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No bother pal, thanks
 
Right I've spoken to kinspan and they never recommend sand and cement render over the top of any of there products, I e in formed the building supplier who arranged the spec and so on and they are basically washing there hands of the bastards, so is the best solution a polymer base coat with mesh then a top coator shall I hack of the top coat of render and put a base of polymer on then a top of coat. Tha nd again guys.
 
No you would go ontop of it all mate , basecoat with fibreglass mesh embedded in it , then a acrylic top coat at colour of there choice . If you started hacking off god knows what would happen lol
 
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