GreenGables Posted November 27, 2022 Share Posted November 27, 2022 Hello. I'd appreciate any advice please. Due to another issue we've just noticed that our builder has not included cavity trays throughout our build as per the plans. The trays should have been placed where external walls become internal (join to flat roofs), over door and window openings and steel, but they have not been done and there are no weep holes either. How much of a problem is this? I understand from reading online that the cavity trays can be retrofitted but is this necessary? This has somehow not been spotted by either the architect or building control. Link to comment Share on other sites More sharing options...
nod Posted November 27, 2022 Share Posted November 27, 2022 Probably not the answer you are hoping for Yes they are necessary and will have to be retro fitted Certainly over all external opening If your builder isn’t prepared to do this You will have to bring a contractor in and take your builder to court Trays normally take 10 minutes per opening Retro May take most of a day per opening Link to comment Share on other sites More sharing options...
Miek Posted November 27, 2022 Share Posted November 27, 2022 Really, this is basic stuff, the builder is taking the piss. Way more work to retrofit what is a super easy job in the first place. Link to comment Share on other sites More sharing options...
Conor Posted November 27, 2022 Share Posted November 27, 2022 Is your architect supervising the job or just stage inspections etc? Either way, need them or an independent engineer/surveyor to do an inspection. If this was missed, what else was? I hope it was a one off and you get it sorted. Link to comment Share on other sites More sharing options...
Dave Jones Posted November 27, 2022 Share Posted November 27, 2022 who is managing the build ? If not you then its down to them to sort. Link to comment Share on other sites More sharing options...
GreenGables Posted November 27, 2022 Author Share Posted November 27, 2022 The architect is administering the contract and doing regular inspections for valuation. I’m shocked this was missed. It’s so clear in the plans. Wouldn’t building control have checked? Link to comment Share on other sites More sharing options...
nod Posted November 27, 2022 Share Posted November 27, 2022 9 minutes ago, GreenGables said: The architect is administering the contract and doing regular inspections for valuation. I’m shocked this was missed. It’s so clear in the plans. Wouldn’t building control have checked? I presumed from your original post this was a small self managed job Yes BC should have picked this up It’s now up to your Architect to sort this out Poor management on his or her part Link to comment Share on other sites More sharing options...
GreenGables Posted November 27, 2022 Author Share Posted November 27, 2022 Are there lintels that don’t require cavity trays, so the lintel acts as a cavity tray? Link to comment Share on other sites More sharing options...
Kelvin Posted November 27, 2022 Share Posted November 27, 2022 Depends on the lintel. Some are designed to guide water to the weep holes. Reinforced concrete lintels will need a tray. Link to comment Share on other sites More sharing options...
GreenGables Posted November 27, 2022 Author Share Posted November 27, 2022 Here is a photo I took during the build. It’s an insulated steel lintel. Would this need a cavity tray? Link to comment Share on other sites More sharing options...
Kelvin Posted November 27, 2022 Share Posted November 27, 2022 (edited) Look at the spec for the lintel that was installed. Catnic do lintels that have a DPC ‘built in’ which look much like the one in your picture. https://catnic.com/products/lintels/overview/steel-lintels-for-cavity-walls Edited November 27, 2022 by Kelvin Link to comment Share on other sites More sharing options...
GreenGables Posted November 27, 2022 Author Share Posted November 27, 2022 16 minutes ago, Kelvin said: Look at the spec for the lintel that was installed. Catnic do lintels that have a DPC ‘built in’ which look much like the one in your picture. https://catnic.com/products/lintels/overview/steel-lintels-for-cavity-walls Thanks Kelvin, I’ll check with the architect. Hopefully that’s what was used. Link to comment Share on other sites More sharing options...
HughF Posted November 28, 2022 Share Posted November 28, 2022 Brick outer leaf? If so, definitely required. If you were going render onto block then it’s questionable whether they’re required. Our house hasn’t got them and we don’t have any damp issues. 1 Link to comment Share on other sites More sharing options...
Gus Potter Posted November 28, 2022 Share Posted November 28, 2022 44 minutes ago, HughF said: If you were going render onto block then it’s questionable whether they’re required. Yes a bit depends on the exposure.. normally they would always be included but if your back is against the wall then sometimes a case can be made for not having them if the outside leaf is rendered. On 27/11/2022 at 09:01, GreenGables said: The architect is administering the contract There is a big difference between contract administration and site supervision / clerk of works function. Best to check what agreement you have with your Architect. Link to comment Share on other sites More sharing options...
ETC Posted November 28, 2022 Share Posted November 28, 2022 Stepped DPC and weep vents should really be installed. Some steel lintel manufacturer’s will have the requirement for a stepped DPC in their small print and on any relevant (installation) BBA Certificate. Building Control should have picked this up. Have you asked them if they did pick it up and have they informed the builder? Normal practice to inform the builder of issues at the end of an inspection. BC may also have issued a letter to you (the applicant?) in relation to the missing DPC. I had the same issue on site a couple of months ago. Builder had to retro fit them. Link to comment Share on other sites More sharing options...
GreenGables Posted November 29, 2022 Author Share Posted November 29, 2022 Thanks ETC, We are now working to establish where cavity trays are missing. It looks like there are some thankfully, but large areas have been missed especially over lintels and around parapet roofs. We will then speak to Building Control to find out if they noticed and make a plan for retrofit as necessary. On parapet roofs for example are they essential, or could we seal the tops over the cavities (under copings) and then waterproof the facing brickwork with permagard cream or similar? We are checking with the lintel manufacturer if the lintels need protection. Thanks for all the advice. Link to comment Share on other sites More sharing options...
ETC Posted November 29, 2022 Share Posted November 29, 2022 If you completely seal the inside skin and the top of the parapet wall a cavity tray may not be required. I’d always specify one anyway if the height of the parapet is high. Belt and braces. Look at the Sarnafil/Trocal details for inspiration. Link to comment Share on other sites More sharing options...
Dave Jones Posted November 30, 2022 Share Posted November 30, 2022 if they missing elecmentary items like trays check they have put in any DPC at all. Link to comment Share on other sites More sharing options...
GreenGables Posted November 30, 2022 Author Share Posted November 30, 2022 35 minutes ago, Dave Jones said: if they missing elecmentary items like trays check they have put in any DPC at all. Thankfully I’ve got photos which show the dpc is in place. What else is worth checking at this stage?. I am shocked building control didn’t pick this up. Link to comment Share on other sites More sharing options...
GreenGables Posted November 30, 2022 Author Share Posted November 30, 2022 23 hours ago, ETC said: If you completely seal the inside skin and the top of the parapet wall a cavity tray may not be required. I’d always specify one anyway if the height of the parapet is high. Belt and braces. Look at the Sarnafil/Trocal details for inspiration. The parapet isn’t high inside so we may be able to do without. Everything is being checked. Link to comment Share on other sites More sharing options...
GreenGables Posted December 4, 2022 Author Share Posted December 4, 2022 We've been checking back through all our photos of the build and see that no cavity trays have been added over upstairs window lintels. Are they needed and can they be retrofitted here if the roof is on? Thank you . Link to comment Share on other sites More sharing options...
MJNewton Posted December 4, 2022 Share Posted December 4, 2022 2 hours ago, GreenGables said: Are they needed Not in that instance as the roof overhang prevents any rain hitting and going through the wall (indeed, what wall?!). Link to comment Share on other sites More sharing options...
Canski Posted December 4, 2022 Share Posted December 4, 2022 Not needed there Link to comment Share on other sites More sharing options...
Mr Punter Posted December 4, 2022 Share Posted December 4, 2022 I often see bricklayers putting in cavity trays and weeps when there is almost no brickwork above. Completely pointless. Link to comment Share on other sites More sharing options...
GreenGables Posted December 4, 2022 Author Share Posted December 4, 2022 Thank you both. That’s good news. Link to comment Share on other sites More sharing options...
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