epsilonGreedy Posted February 16, 2021 Share Posted February 16, 2021 I have a sheet of 18mm exterior grade plywood which is comprised of about 10 layers. Does it resist bending better in any particular orientation? My guess is the laminate layers are oriented at 90 degrees to each other hence the sheet should be strong both along the length and width of the 8x4 sheet. I am going to liminate two 18mm cut outs 900mm x 250mm with West Systems epoxy and fix these diagonally across the corner of my roof wall plate. Once this ply corner tie is fixed down to the wallplate I will then screw a metal strap with a 90 degree twist onto the ply corner tie and screw the other end of the metal strap to the bottom of the hip rafter. The combined structure will function as a hip rafter dragon tie. 1 Link to comment Share on other sites More sharing options...
TonyT Posted February 16, 2021 Share Posted February 16, 2021 https://www.strongtie.co.uk/products/detail/hip-ridge-connector/342 one of these work instead? Link to comment Share on other sites More sharing options...
SteamyTea Posted February 16, 2021 Share Posted February 16, 2021 JFGI http://www.woodbin.com/calcs/sagulator/ Link to comment Share on other sites More sharing options...
Russell griffiths Posted February 16, 2021 Share Posted February 16, 2021 Nope, just mark it up and cut it out, glue it screw it. Just get it fookin on and get onto the next bit. Link to comment Share on other sites More sharing options...
joe90 Posted February 16, 2021 Share Posted February 16, 2021 6 hours ago, TonyT said: https://www.strongtie.co.uk/products/detail/hip-ridge-connector/342 one of these work instead? No, they are for the ridge. 6 hours ago, epsilonGreedy said: Does it resist bending better in any particular orientation? No 6 hours ago, epsilonGreedy said: I am going to liminate two 18mm cut outs 900mm x 250mm with West Systems epoxy and fix these diagonally across the corner of my roof wall plate. Once this ply corner tie is fixed down to the wallplate I will then screw a metal strap with a 90 degree twist onto the ply corner tie and screw the other end of the metal strap to the bottom of the hip rafter. The combined structure will function as a hip rafter dragon tie. We did this on my hip roof just using 4x2 across the corner, good detail but think epoxy glue etc may be overkill just annular ring shank nails into the wall plate ? 2 Link to comment Share on other sites More sharing options...
Mr Punter Posted February 16, 2021 Share Posted February 16, 2021 The ply orientation will not make any odds. You could use OSB if there is no ply about. Any glue will be OK or none if you don't have any. This is prob mostly a detail that get omitted but your drawing looks fine. Get on with it before someone felt and battens and you can't get to it. 1 Link to comment Share on other sites More sharing options...
epsilonGreedy Posted February 17, 2021 Author Share Posted February 17, 2021 16 hours ago, SteamyTea said: JFGI http://www.woodbin.com/calcs/sagulator/ Nice link. Having overcome my initial shock at the calculator complexity I input the numbers for my plywood wallplate tie and the calculator did not register much flex (0.5mm) until I increased the force to 250kg. Most of the force at the hip end will be a horizontal sheer as the weight of the slates might provoke the hip rafter to slip outwards from its footing at the wall plate. Given a total slate weight of about 3 tons spread across 6 hips and multiple trusses the force is low. The more significant risk would be a 100mph gust across the top of the hip ridge causing lift. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted February 17, 2021 Author Share Posted February 17, 2021 13 hours ago, Mr Punter said: The ply orientation will not make any odds. You could use OSB if there is no ply about. Any glue will be OK or none if you don't have any. This is prob mostly a detail that get omitted but your drawing looks fine. Thanks. The drawing was lifted off an NHBC technical web page. Despite the forum's general downer on the NHBC I do find their technical material useful. 13 hours ago, Mr Punter said: Get on with it before someone felt and battens and you can't get to it. It will be tight in that corner, the main 30 degree roof pitch translates into a 22 degree pitch along the hip raters. I am already worried about the practicalities of getting attic insulation in these corners and tucked into the top of the cavity. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted February 17, 2021 Author Share Posted February 17, 2021 15 hours ago, joe90 said: We did this on my hip roof just using 4x2 across the corner, good detail but think epoxy glue etc may be overkill just annular ring shank nails into the wall plate ? The yachtsman in me views West Systems epoxy as a wonder glue. I have previously concluded that builders do not understand ropes, tarpaulins or epoxy glue ? Previously on this forum expert builders had told me my tarpaulin roof would not last 24 hours. Two months later it is coping well, must be due to all that practice I had tying down winter boat covers. 1 Link to comment Share on other sites More sharing options...
epsilonGreedy Posted February 17, 2021 Author Share Posted February 17, 2021 21 hours ago, TonyT said: https://www.strongtie.co.uk/products/detail/hip-ridge-connector/342 one of these work instead? Interesting, not seen one of these before. So far I have managed to get a nice tight fit between the rafters at the ridge/hip junction by tweaking the angles on my compound mitre saw. When I got the truss manufacturer back onsite to review my interim roofing work he said that my proposal to add a few shaped wood infills at the hip rafter junctions would be a nice but OTT reinforcement. Think I will skip this metal bracket because it could interfere with the wooden roll tops if I decide to go for lead flashing ridges. Link to comment Share on other sites More sharing options...
joe90 Posted February 17, 2021 Share Posted February 17, 2021 50 minutes ago, epsilonGreedy said: Think I will skip this metal bracket because it could interfere with the wooden roll tops if I decide to go for lead flashing ridges. It shouldn’t do as it fits the sides and bottom of the ridge and hip timbers, not the top!. Link to comment Share on other sites More sharing options...
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