TRUDI Posted February 3, 2019 Share Posted February 3, 2019 We have completed a closed panel timber frame self build with MGO internal board. We have huge issues with plaster - cracks on on every joint, bowing to every panel and cracks through coving & cracking tiles. We have been advised that this is because the wrong bonding agent was used but no-one seems to know how to repair this. We have been assured that structurally it is sound - the damage is cosmetic but of course expensive (& not covered by structural warranty or site insurance). Suggestions to repair are easifill (tried & better but hairline cracks have reappeared), acrylic filler or complete re-boarding. Has anyone else had similar issues or can help in anyway?? Any assistance would be gratefully received, as we feel that everyone is shutting up shop and we are going round in circles!! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 3, 2019 Share Posted February 3, 2019 Welcome. Sounds like an interesting problem. As you say this is a closed panel system, presumably it was manufactured off-site as prefabricated panels, is that right? If so, then what does the closed manufacturer have to say about the problem? I looked at an MgO closed panel system a few years ago and have to say it looked pretty good, my only concern was traceability of the MgO boards, as the manufacturer was bringing them in from China and I wasn't 100% convinced they had the proper BBA certificate. The only thing I can remember that may have a bearing on your problem is that MgO boards need very rigid fixings, made from materials that will not corrode (because of the possibility of chlorides coming from the panel material if it gets damp during construction). The need for very rigid fixings seems to be associated with the need to try and limit movement from thermal expansion. I've certainly heard of thermal expansion causing problems with MgO boards, but usually bowing off the wall, rather than cracking along the joints. Cracking sounds to me as if the fixings may not be adequate, perhaps. There are special screws for fixing MgO that are both corrosion resistant and have a sharper angle under the head, with little nibs to ensure that they countersink properly. Were these used to fasten the boards? Link to comment Share on other sites More sharing options...
Mr Punter Posted February 3, 2019 Share Posted February 3, 2019 I thought that MgO was normally used for external sheathing instead of OSB. Was it scrim taped and coated with multi finish? Link to comment Share on other sites More sharing options...
scottishjohn Posted February 3, 2019 Share Posted February 3, 2019 (edited) If it is timber frame ,they are well known for shrinking as wood dries out -,which could be causing cracks in joints and bending of the MGo boards ? were the panels well protected from water when on site before assembly Edited February 3, 2019 by scottishjohn Link to comment Share on other sites More sharing options...
Ferdinand Posted February 3, 2019 Share Posted February 3, 2019 2 hours ago, TRUDI said: We have completed a closed panel timber frame self build with MGO internal board. We have huge issues with plaster - cracks on on every joint, bowing to every panel and cracks through coving & cracking tiles. We have been advised that this is because the wrong bonding agent was used but no-one seems to know how to repair this. We have been assured that structurally it is sound - the damage is cosmetic but of course expensive (& not covered by structural warranty or site insurance). Suggestions to repair are easifill (tried & better but hairline cracks have reappeared), acrylic filler or complete re-boarding. Has anyone else had similar issues or can help in anyway?? Any assistance would be gratefully received, as we feel that everyone is shutting up shop and we are going round in circles!! Welcome. Link to comment Share on other sites More sharing options...
nod Posted February 3, 2019 Share Posted February 3, 2019 Shrinkage is more likely If was a matter of the wrong bonding agent You could get tandem areas blowing But cracking like you have described will be down to the structure under the boards The majority of my work is plastering or tiling onto MF framing We always have far more snagging on timber As already pointed out It drys out But even with the MF We always add deflection heads to allow movement Link to comment Share on other sites More sharing options...
John malone Posted October 31, 2019 Share Posted October 31, 2019 MGO is open vented breathable board using PVA based products will lead to issues you must always us acrylic products to slow the curing time down when using multi finish products such as blue grit and others will not work with MGO Link to comment Share on other sites More sharing options...
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