epsilonGreedy Posted May 7, 2018 Share Posted May 7, 2018 Talking to a potential slate tile roofer the other day he said he had not encountered a cut roof on a new build in recent years. Does cost rule them out? My house will have a 30 degree all-hipped roof and the L-shape creates one valley. Further complexity arises from the utility L portion of the roof having a slightly lower ridge than the main block, I also want some usable attic storage space in what is a smallish house short of storage space. Reading the House Builders Bible (HBB) I got the impression that attic cut prefab trusses bump up cost and so will the valley plus the ridge complexity. My reading of the HBB is that my roof will be close to the point where a cut roof is a reasonable option from a cost perspective. Now I am wondering about the experience of the roofer. Link to comment Share on other sites More sharing options...
ProDave Posted May 7, 2018 Share Posted May 7, 2018 My house has a cut roof and probably pretty much any house with a ridge beam and vaulted ceilings. Link to comment Share on other sites More sharing options...
Stones Posted May 7, 2018 Share Posted May 7, 2018 Mine has a mix of trusses and ridge beam / cut rafters. Depends on complexity of your build and what you want to achieve internally. Link to comment Share on other sites More sharing options...
PeterW Posted May 7, 2018 Share Posted May 7, 2018 Same here. Full cut roof, 2 big valleys, 3 full lead dormers each with a pair of lead valleys and 6 Velux rooflights... We we could have gone with an attic truss with a drop chord to give me the floor too but there were too many cut bits to do to fit between the trusses it wasn’t worth it. A big cut roof with no traditional ceiling joists need steels at purlin or ridge and these need detailing carefully. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted May 7, 2018 Author Share Posted May 7, 2018 9 minutes ago, Stones said: Mine has a mix of trusses and ridge beam / cut rafters. Depends on complexity of your build and what you want to achieve internally. A limit on ridge height might mean the ceiling joists will intersect with the rafters higher than the wall plate. I also want to create some attic storage under the ridge portion of the hipped roof on the main block, a 4m x 3m floor plan for the storage would be fine. There are no other plans to utilize the roof space, conventional flat ceilings are planned. Link to comment Share on other sites More sharing options...
PeterW Posted May 7, 2018 Share Posted May 7, 2018 Just now, epsilonGreedy said: A limit on ridge height might mean the ceiling joists will intersect with the rafters higher than the wall plate. I also want to create some attic storage under the ridge portion of the hipped roof on the main block, a 4m x 3m floor plan for the storage would be fine. There are no other plans to utilize the roof space, conventional flat ceilings are planned. Ok so you will either need an engineered truss or a cut roof with steels as purlins just above the sloping ceiling height. Have you tried the truss manufacturers ..? DWB in Hull would design and cut the whole roof for you - they also do engineered joists for the first floor and will use engineered joists for rafters too if you need to get the depth for insulation. 1 Link to comment Share on other sites More sharing options...
epsilonGreedy Posted May 7, 2018 Author Share Posted May 7, 2018 15 minutes ago, PeterW said: A big cut roof with no traditional ceiling joists need steels at purlin or ridge and these need detailing carefully. The roofer's comment about not seeing a cut roof in years is either a reflection of the budget jobs he undertakes or perhaps the poor state of the local economy means well speced self builds are few and far between. The largest roof segment will be 10m x 6m by external wall plan and there will be ceiling joists. Does this count as a big cut roof? Link to comment Share on other sites More sharing options...
ProDave Posted May 7, 2018 Share Posted May 7, 2018 6 minutes ago, epsilonGreedy said: A limit on ridge height might mean the ceiling joists will intersect with the rafters higher than the wall plate. I also want to create some attic storage under the ridge portion of the hipped roof on the main block, a 4m x 3m floor plan for the storage would be fine. There are no other plans to utilize the roof space, conventional flat ceilings are planned. You need attic trusses. Common up here for part room in roof houses. It also gives you an uncluttered loft space. For hipped roofs they make a set where the end trusses are shaped to the hip, or that but can be cut on site. 1 Link to comment Share on other sites More sharing options...
epsilonGreedy Posted May 7, 2018 Author Share Posted May 7, 2018 10 minutes ago, PeterW said: Ok so you will either need an engineered truss or a cut roof with steels as purlins just above the sloping ceiling height. Is an attic truss an example of an engineered truss or is any truss where the joist does not rest on the wall plate, deemed to be engineered? I am surprised to read I might need steel purlins as I have been watching Aussie and Yankee YouTube videos showing hipped roofs being cut on site with nothing more complex than a graduated measuring triangle and lots of wood. Link to comment Share on other sites More sharing options...
Ferdinand Posted May 7, 2018 Share Posted May 7, 2018 We are all really closet Victorians where roofs are concerned ?. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted May 7, 2018 Author Share Posted May 7, 2018 14 minutes ago, ProDave said: You need attic trusses. Common up here for part room in roof houses. It also gives you an uncluttered loft space. Thanks. Between posts I was doing some simple geometry and now realize that given my 10 x 6 size of the main house, then by definition the main ridge is only 4 meters long. Previously I had imagined the main roof been comprised of regular fink and attic trussed under the main ridge, this felt like a recipe for mathematical disaster at the remote cutting shop. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted May 7, 2018 Author Share Posted May 7, 2018 1 minute ago, Ferdinand said: We are all really closet Victorians where roofs are concerned ?. Do closet Georgians outrank Victorians? Link to comment Share on other sites More sharing options...
PeterW Posted May 7, 2018 Share Posted May 7, 2018 7 minutes ago, epsilonGreedy said: Is an attic truss an example of an engineered truss or is any truss where the joist does not rest on the wall plate, deemed to be engineered? I am surprised to read I might need steel purlins as I have been watching Aussie and Yankee YouTube videos showing hipped roofs being cut on site with nothing more complex than a graduated measuring triangle and lots of wood. Treat anything not cut and fitted on site as engineered and you won’t go far wrong. So so as I look at your roof layout you have a full run down the back of the house that is circa 8-10m which is going to need a support somewhere on the midpoint of each rafter. Unless you go with a glulam beam that will be probably 400mm deep, you will not get the depth and length from a UK timber yard without splicing and you don’t seem to have many internal structural walls ..! The US and Aus can get away with smaller section roof timbers as they rarely use concrete or slate on their rooves so the static loading is less. To put it into perspective, I have 11 tonnes of tiles and 1.3 tonnes of lead on my roof - in shingles or sheet that would be 1/3rd of that at best. Do the maths.... Unless you are an engineer then I would leave the roof design to a specialist. The truss companies will do it for free usually and they give you an accurate design, assurance it’s correct, and most of all the insurance cover if they get it wrong ..!!! Link to comment Share on other sites More sharing options...
ProDave Posted May 7, 2018 Share Posted May 7, 2018 49 minutes ago, epsilonGreedy said: Is an attic truss an example of an engineered truss or is any truss where the joist does not rest on the wall plate, deemed to be engineered? All pre made trusses are engineered. It's just that the truss company doe the sums, makes them to size and certifies them. They provide a roof plan of how to assemble them. Providing you stick to that plan, no other engineering input is normally needed. Link to comment Share on other sites More sharing options...
Ferdinand Posted May 7, 2018 Share Posted May 7, 2018 40 minutes ago, epsilonGreedy said: Do closet Georgians outrank Victorians? In build quality I think they probably don’t. London Georgian houses are notorious imo for being built of all kinds of crud; there are often spontaneous collapses in London. My impression is that the Georgian are worse. Ferdinand Link to comment Share on other sites More sharing options...
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