Stress Patches

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Rigsby

Rigsby

TPF Special Forces
Okie Doke. Carrying on with my obsession with cracking I have always wondered if stress cracks around openings are at 45 degrees to the corners then why do all manufacturers specify that the mesh strands are vertical and horizontal.

If you hold a square of mesh up and pull side to side the horizontal will take the strain and if like wise if you pull top to bottom. But if you pull corner to corner there is no resistance. As 45 degree cracks have no stands at 90 degrees to them then where is the resistance?

I asked this to the clowns at Weber and all they said is do what it says in the book which is V & H. All the others appear the same but SAS said if there is room then put a 300mm x 300mm min patch on top of the stress patch at 45 degrees as well and this will help. They did remind me that some stress cracks are vertical from window corners and usually join up to another opening corner below or above or an interference in the substrate like soil pipe or flues. I had a stress crack go from window corner to a down pipe bracket screw (45d)

What's your thoughts on the statutory vertical and horizontal stress patch?
 
its all bullshit. stress cracks if its going 2 crack its going to crack. u can do f uck all about it
 
My chemist said to put them on your temple rather than your forehead will give it a try tomorrow.
 
theclemo said:
its all bullshit. stress cracks if its going 2 crack its going to crack. u can do f uck all about it
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Not necessarily. A structural crack will tear mesh but render is under strain all over and a weak point like a corner can encourage a crack. My point with the manufacturers is it ought to be both ways 90 & 45 at corners.

As far as I know I have never had S&C crack on me at openings but I have had mono with V&H mesh installed. I know why Mono is more prone to cracking than S&C but I won't go it that right now. The manufacturers will also know why and their techs apart from Weber who agree with my theory but they get there advice from someone else.

Blone is right, and I fully mesh (now) all the base coat and chuck in the said 45 patch plus the standard manufacturers spec on the stress patches in the mono. Not had a crack since but does anyone else do a 45 degrees patch? L&D sell stress patches that are cut for 45d so someone uses them.

I have got 2 manufacturers specs who in their thin coat systems spec full mesh V&H and then 45d patches as well on opening corners but only thin coat? Why not thick coat?
 
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theclemo said:
its all bullshit. stress cracks if its going 2 crack its going to crack. u can do f uck all about it
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That's not what I've found mate. On one long running site a particular design of house kept cracking in roughly the same place. I tried using EML before first coating but still it would crack, paper and wire and sometimes it would stop it but not always. I then tried mesh in the scratch coat and voila no more cracks. This was using S&C not mono.
 
I use the pre cut so called stress patches on the odd occasion when the jobs a good payer and more work could be obtained, otherwise just mesh above and below windows and don't have problems with mono cracking, even weber! Mesh won't hold a building together because they are constructed from segmental pieces of masonary.
 
always mesh above and below windows,
aint worth the chance, mesh works out at roughly a pound a square meter, so its small beer.
 
Can you use this mesh stuff under multifinish ? Would it be better stopping cracking than skrim for example ? Thanks in advance guys
 
On new build you do have a get out of jail free card with stress cracks on openings. The manufacturers will expect reinforcing mesh in the block laying gobbo 1 & 2 courses above and below the openings. This rarely gets done and that's your get out clause! A metal detector will establish whether there is one or not.

Refurb is a bit more difficult so its full mesh as described below.

Chinese mesh is cheap and useless in the long term. The german stuff is £65 + vat a roll (Weber). Anyone know of the german made mesh any cheaper.
 
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Yes, we have used the 160g m2 in over skim situations where an existing wall has had a lot of cracks ( but not blown) typically a cement backing coat that was too strong a mix and displays signs of crazing.The resultant work has been succesful. Remember to factor in at least £1 to £1.50 for the scrim and the extra labour for applyng into the 1st coat of skim.
 
I saw a contractor pebbledashing a local council estate with that over dash polymer gear. They take of any loose and then fungicide wash. Build up any hollows and holes then give it a skim over, bed full mesh then skim over again and dash.

When they skimmed over they pinned back the mesh with hammer fix mushroom head pins. Bear in mind they are going through 5-6mm of wet render into the old dashing behind, these pins will be short. The only pins I can find are the insulation ones or the type for tanking membranes. Anyone know who sells them?
 
Rigsby said:
On new build you do have a get out of jail free card with stress cracks on openings. The manufacturers will expect reinforcing mesh in the block laying gobbo 1 & 2 courses above and below the openings. This rarely gets done and that's your get out clause! A metal detector will establish whether there is one or not.

Refurb is a bit more difficult so its full mesh as described below.

Rigsby, I worked on a large new build this year, the contractor was crack paranoid. He used 7 newton block with stainless mesh bedded in every 3rd joint. I kid you not. The building was left for a fair while before rendering comenced. Now this building still showed very faint vertical stress cracks both above and below some window opening. He was very nervous at this finding.

We meshclothed around all opening as you would, and doubled up on areas where cracks were noted. The building was 2 coated with CPI rendermix and no signs of any hair lines to date.

Chinese mesh is cheap and useless in the long term. The german stuff is £65 + vat a roll (Weber). Anyone know of the german made mesh any cheaper.
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mesh
 
Rigsby said:
Chinese mesh is cheap and useless in the long term.
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I've used some of this Chinese gear on S&C renders and haven't noticed any problems, it seems pretty tough. Is it just a strength issue that you see as a problem with this stuff?
 
Rigsby, I worked on a large new build this year, the contractor was crack paranoid. He used 7 newton block with stainless mesh bedded in every 3rd joint. I kid you not. The building was left for a fair while before rendering comenced. Now this building still showed very faint vertical stress cracks both above and below some window openings. He was very nervous at our findings.

We meshclothed around all opening as you would, and doubled up on areas where cracks were noted. The building was 2 coated with CPI rendermix and no signs of any hair lines to date.
 
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essexandy said:
I've used some of this Chinese gear on S&C renders and haven't noticed any problems, it seems pretty tough. Is it just a strength issue that you see as a problem with this stuff?
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If you compare it with the German stuff it is softer but it may still be strong enough for now. It is the Alkaline resisting treatment that it has that lets it down. The Chineses mesh has it sprayed on as a coating as the German gear is soaked in it. The Chinese gear will eventually rot as the German stuff wont.

I suppose it down to your conscience and how long your warranty is. There is also the financial side of it. If the customer is a penny pincher and so long as your warranty (if there is one) is short then the Chinks stuff comes into it's own.

I have a couple of rolls of the slant eyed stuff but only for the cheap skates who deserve nothing better!
 
Oh I see, well I've only used the Chinese stuff on S&C where no one is expecting any mesh to be used at al so not really a problem. I've got a couple of rolls of the pink weber mesh in the unit for use with their gear.
 
Rigsby said:
On new build you do have a get out of jail free card with stress cracks on openings. The manufacturers will expect reinforcing mesh in the block laying gobbo 1 & 2 courses above and below the openings. This rarely gets done and that's your get out clause! A metal detector will establish whether there is one or not.

Refurb is a bit more difficult so its full mesh as described below.

Chinese mesh is cheap and useless in the long term. The german stuff is £65 + vat a roll (Weber). Anyone know of the german made mesh any cheaper.
Click to expand...

i get parex tv10 mesh [same as pink weber but green] for about £47 plus vat so getting on for 20 quid a role less.
 
owls where are you getting ur mesh from parex are great but getting there stuff delivered is a nightmare i tried to order 2 rolls from keyline and parex wanted 60 quid to deliver?? wtf ??
 
Minster was selling Weber mesh for £40 + vat but I think they made a mistake because before it was £65 + vat. For £40 I took 2 years worth lol.
 
pwi said:
owls where are you getting ur mesh from parex are great but getting there stuff delivered is a nightmare i tried to order 2 rolls from keyline and parex wanted 60 quid to deliver?? wtf ??
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howarth timber, theve just recently started stocking the entire parex range
 
Rigsby said:
Okie Doke. Carrying on with my obsession with cracking I have always wondered if stress cracks around openings are at 45 degrees to the corners then why do all manufacturers specify that the mesh strands are vertical and horizontal.

If you hold a square of mesh up and pull side to side the horizontal will take the strain and if like wise if you pull top to bottom. But if you pull corner to corner there is no resistance. As 45 degree cracks have no stands at 90 degrees to them then where is the resistance?

I asked this to the clowns at Weber and all they said is do what it says in the book which is V & H. All the others appear the same but SAS said if there is room then put a 300mm x 300mm min patch on top of the stress patch at 45 degrees as well and this will help. They did remind me that some stress cracks are vertical from window corners and usually join up to another opening corner below or above or an interference in the substrate like soil pipe or flues. I had a stress crack go from window corner to a down pipe bracket screw (45d)

What's your thoughts on the statutory vertical and horizontal stress patch?
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FFS John you need to get a fcuking life mate
 
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