Bitpipe

Underlying boards showing through render - suggestions?

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We had the frame renderd back in Dec 15 / Jan 16 just after the frame was erected.

 

System is 25mm battens onto the MBC exterior panel, 12.5mm Gtec Render board, 4mm Parex Maite undercoat with mesh reinforcement, 4mm Parex Maite second coat and 1mm Parex DPR topcoat.

 

Application went well, they were very diligent, only working when the conditions were suitable and the finish looked superb when complete. They were back a few months ago to do the garage and some other areas originally inaccessible.

 

However this last few weeks I've  really noticed the outlines of the underlying boards, especially in direct sunlight and wondering why this is only now obvious and how to remedy.

 

Want to get some wisdom here before engaging with the contractor (who I've always found fair to deal with).

 

I'm wondering if it's just the accumulation of dust on the render or something more serious. 

 

Have to stress, there are no cracks or blown areas etc and the problem is consistent across the house.

 

 

 

 

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Do you like the Tudor look? You could paint all those lines black.....I'll get me coat!

 

Gently wash an area and see if it looks different?

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Did they counter batten and were the battens kiln dried. Several manufactures say counter battening is a no no

 

Also some boards need the joints taping before the first coat, were they taped? 

 

To me it looks like the board had a tapered edge have you a bit left to see

 

 

 

 

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It looks to me as though the boards have shrunk at the edges or the render has pulled into the joints as its dried (and contracted). A bit like pulling a balloon tight over an uneven surface.

 

You often see this type of result in an area that has been painted over and filled area. Its caused by the filler shrinking back over time and also the paint pulling into a differing substrate. Sorry, I have no idea if that's helpful as I know nothing about render systems.

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Thanks all. 

 

No counter batten, just batten onto the external panel of the TF.

 

Boards were square cut, not taped but tightly butted up and the render process was pretty thorough, acres of green poly mesh between coats etc.

 

I'll try and clean a bit to see if there's any difference - running my hand over its amost completely smooth, no noticeable depression.

 

Strange thing is why it's only noticeable now - I'd have been straight on it even a few months ago when they came back to do the garage.

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How about some faux stitching and it'd look like a quilt / puffer jacket? :)

 

Is this like the leopard spotting I've seen with some EWI? I'd be well peed off tbh.

 

It's not to do with heat is it?

 

(A weird analogy but the old Fibre Sports bonded on X-packs on Capris were ace from the Ford dealers. Aftermarket jobs affixed with pop rivets improperly, used to show up where the pop rivets got hot in the sun and showed thru the paint).

 

 

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I think it is to do with a big flat panel the angle of the sun and the light colour. 

I bet if you put a straight edge on it, it will look really good with hardly any gaps behind the straight edge, but to the eye with that white you will pick it out. 

Have you ever looked at a poor spray job on a car? You can spot it a mile away in the right light, but at other times you would never know. 

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Talking to Joe from MBC, he thinks its lack of expansion joints in the render board.

 

Have taken it up with the contractor, will see what they say. I think the recent warm spell has exacerbated what ever the underlying issue is.

 

 

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11 minutes ago, Bitpipe said:

Talking to Joe from MBC, he thinks its lack of expansion joints in the render board.

 

15 hours ago, Bitpipe said:

Boards were square cut, not taped but tightly butted up

 

Seems plausible. Hope you get the right answer from the contractor.

 

 

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That explanation sounds like the right one - the heat causes the boards to expand, and as they are constrained at the edges that expansion causes them to bow out.  Once they've bowed out they may well have pulled the fastenings out a bit, probably the batten fastenings rather than the panel ones.  That then stops the panels going flat again when they cool down.

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Start with the contractor, they will get in touch with Parex, who will send a rep out who will know what has caused the problem and suggest a fix.

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Both the specifications that i had prepared by the manufacturers specified a movement joint at 1st floor joist level. They also stated a 3-5mm gap must be left between the boards for expansion. 

ProRend did not require taping but Knaff did 

 

 

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Have had an email exchange with Parex rep (kindly supplied by PM) who confirm that the render board expansion gap is the likely issue, further compounded by the render board used not being one of their approved types. I need to review the site video and photos to see if I can determine the render board expansion gapping.

 

My error was accepting the installer's spec and not knowing that I could/should have checked it with Parex first. 

 

So, installer is coming out to survey but feels like the remedy is to take it back to batten and re-do, which will be significantly expensive for them (especially when scaff etc is included) so I can't imagine them offering that willingly.

 

Any suggestions on how to take the next steps to ensure that it's put right? 

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I would ask your rendering contractor to put it right. Don't take any of the blame yourself, if you asked for a Parex system they should provide a Parex system, are they approved Parex contractors? Parex won't offer any guarantee (not that its worth much) if they haven't been on their course.

 

If the contractor refuses to redo it see if he will come back for a site meeting with the Parex rep.

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Thanks, i'm not accepting any blame, just realising that there was more due diligence that could have been done.

 

Installer coming to site on Friday so will see what he says, will keep my powder dry on the information from Parex.

 

They're not fly by night contractors and when one of their guys accidentally scratched one of our alu framed doors with a float (despite applying protection etc) they were quick to pay to have it repaired so hoping that they do the right thing.

 

Now that the weather has cooled, the effect is more subtle but still noticeable.

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I can't offer any help, but best of luck with this.

 

Agree with what others have said: you paid a professional to do the job. He should be familiar with what board to use and how to install it.

 

That said, it's surprising that someone who clearly knows what they're doing would make this sort of rookie mistake. Maybe the guys installing the boards were less experienced?

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Just an idea, but can expansion slots be cut in and then finished over?

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Installer's site manager came out and straight away agreed that it's not right. He's bringing Parex rep (who I've also been talking to) on site and will discuss remediation with them.

 

Best case is if they determine that the boards have moved as much as they will, in which case it's a re-application of a base and top coat. More serious if the boards themselves need attention.

 

Stay tuned, must say I'm a bit more relaxed now that they're not running away from the problem.

 

 

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On ‎26‎/‎07‎/‎2017 at 11:21, Vijay said:

Just an idea, but can expansion slots be cut in and then finished over?

 

I've got to be honest I think this is a bad idea.

 

This would cut through the mesh which stops the render cracking, even if it was patched up it would not be ideal. I don't think you would get the render off without damaging the ewi boards. Even if these problems could be overcome, the colour would not match exactly so would need to paint it, but then what is the point of paying for through coloured monocouche?

 

I imagine they will want you to accept that it is painted (if its not out of plumb and it turns out they have actually used the correct boards). It will be up to you to consider if that's acceptable or not.

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13 minutes ago, bassanclan said:

 

I've got to be honest I think this is a bad idea.

 

This would cut through the mesh which stops the render cracking, even if it was patched up it would not be ideal. I don't think you would get the render off without damaging the ewi boards. Even if these problems could be overcome, the colour would not match exactly so would need to paint it, but then what is the point of paying for through coloured monocouche?

 

I imagine they will want you to accept that it is painted (if its not out of plumb and it turns out they have actually used the correct boards). It will be up to you to consider if that's acceptable or not.

 

Just to be clear, these are not EWI boards but standard 12.5mm renderboard.

 

No, whats been initially proposed is whole new layer of Maite (undercoat), mesh and DPR (topcoat) - subject to the option of Parex obv.

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On 27/07/2017 at 13:22, bassanclan said:

 

I've got to be honest I think this is a bad idea.

 

This would cut through the mesh which stops the render cracking, even if it was patched up it would not be ideal. I don't think you would get the render off without damaging the ewi boards. Even if these problems could be overcome, the colour would not match exactly so would need to paint it, but then what is the point of paying for through coloured monocouche?

 

I imagine they will want you to accept that it is painted (if its not out of plumb and it turns out they have actually used the correct boards). It will be up to you to consider if that's acceptable or not.

 

Just had director of render firm plus local Parex rep round. Board rep couldn't make it today but is planned to visit at some point. There is a definite 3-4mm dip between boards now when putting a straightedge over the top. Boards do not seem to have any give and the system is intact, no cracks.

 

If they're all confident that the boards have settled into their final position then they will apply a top coat of maite, mesh and DPR (top coat) all round. We have generous reveals and drip gaps on the cills and other fascia so no issue there.

 

May get away with using a scissor lift vs scaff.

 

If they think the boards are subject to more movement then something more radical will be required.

 

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Glad to hear they're taking responsibility.

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I wonder why the boards are moving.

Surely there is always going to be a problem with expansion and contraction in the heat/cold.

Why are the boards "wrong"

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1 hour ago, bassanclan said:

I wonder why the boards are moving.

Surely there is always going to be a problem with expansion and contraction in the heat/cold.

Why are the boards "wrong"

 

This is exactly what they need to understand - nothing's happening until then.

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