How to support a cathedral ceiling or vaulted roof

we're looking here at a small single storey extension and what you've got here is a typical tied roof you can see here that it's triangulated because you've got the rafters at the top you've got the ceiling tie tying everything together so the forces form a triangle so what happens if you want a vaulted roof a cathedral style ceiling and therefore you need to take this ceiling tie out well let's demonstrate this we'll remove it now and we can see now that if we have any load on this roof so we're going to put tiles up here there may be snow that settles on here there will be a vertical um reaction so coming from the wall plate reacting here at the end pushing upwards to counteract the vertical load and on the wall plate on this side vertically up counteracting the vertical load from above now the issue is is that this isn't a flat roof so there's going to be a horizontal component coming down this rafter and this rafter trying to push out at the wall plate and a wall cannot resist any horizontal load or only a very small amount before it basically starts to push over so we either have to have the ceiling tie in here or what we have to do is support here at the ridge so what we can do is put a steel beam in here looking now at the way that the loads work we've now got a vertical reaction at the steel beam and at each wall plate so there's a vertical reaction here here and here but what about the horizontal reaction that's coming because these are angled well what we have here at the top is that we get rid of this ridge board and that we actually join these together and make sure that they're well connected over the top so the horizontal pulling force this way counteracts the pulling force that way now let's just take away the beam again and put the ridge board back in because that's tying force that reaction is still there even if we don't have the beam but it's in the other direction we've got this pushing against the opposite rafter which is pushing in the same manner but in the opposite direction now because these two are resting together they're pushing together against the ridge board that's why you have the counteracting reaction pushing this way and this way at the wall plate which the wall isn't able to withstand so if we put this steel in here let's have a look at where it actually goes so to do this we're going to need some color so we can see here the steel beam is going from the wall of the original building here because the extension is extending out from the original building and let's just get rid of the section cut so here we've got the full drawing of the building and we'll get and we'll get rid again of the ridge board so we can see that this steel is supported on the gable end and it's supported on the original external wall of the house which we're extending so if we look at this on plan we've got a support here and a support here and each rafter is supporting at the ridge on this ridge beam so we've got a beam here each one of these rafters also is a beam spanning from the wall plate to this ridge beam and as we saw earlier having done this we now don't have any horizontal reaction at the wall plate and that's what we do if we want a vaulted or a cathedral ceiling now the issue here is if we look at the gable end is that this section here is blocking all the light so actually we want to get rid of that and most of the time when we have a vaulted ceiling we will have also an open gable frame so let's get rid of this lintel and you can straight away see now what the issue is here we've now got a ridge beam that isn't supported at this end so how are we going to support that the way i suggest this should be done and is usually done is with a steel a-frame and we'll color this in red so that we can see what's going on so we can see where this is going i'll just remove these two piers so we can see that this a frame is going to be extended a bit further than this actually to go down onto the foundation we've basically got a square hollow section post or a rectangular holo section that goes all the way up and over and down the other side and this has to be a fully welded frame because it's a moment frame or goal post frame and it's supporting simply the ridge beam here let's just hide the rafters and what we'll have here is some kind of connection we'll have a plate a thin plate probably that will go onto here that will get welded here we'll probably have some kind of gusset plate in there and then the holes will go in this plate to bolt it to this to the steel ridge beam so that's basically how you do a vaulted ceiling for a single storey extension let's bring everything back again because the other advantage of this is that what we can now do is reduce these peers the dimensions of this in the uk needs to be 665 or thereabouts but with this moment framing here this is taking the lateral wind loading that this pier usually would take so what we can do now is reduce the size of these so this one this inside pier here can be removed completely and this one we can push back so once this is clad out we can have a totally smooth or nearly smooth transition through from the wall to the window so let's just do this side as well and you can see now the amount of light that's going to be able to go in here obviously this needs now a glazing frame put in there but essentially this stability is taken care of by this frame because any of the wind that's blowing on this side or the or the other side will get transferred through the wall the wall plate the rafters and the ridge beam to this frame which is also connected into to the wall here and to the wall plate there so that's how i would do a single storey vaulted roof extension the other thing possibly to think about is that you would have some timbers coming just across here a collar tie just under the steel beam just to help you form that slight flat section of the roof there now if you want to get hold of this 3d model so that you can interrogate it and see what's going on here i'm thinking about maybe making these available so if you just leave your thoughts in the comments either whether you would find that useful or not then i might think about making these available as a download do please like and subscribe this and do please leave your comments particularly if you're in the trade and you have any thoughts about the buildability of this a lot of builders don't like mixing steel work with timber and they actually prefer to just go with a more simple solution which would be the lintel across here and then the gable masonry but as we've seen that cut out quite a lot of the light and the benefit of having this vaulted roof and this can be mitigated by having roof lights which we would form by moving some of these rafters so essentially most of the time you just double them up and then you can create your roof light in there and then we'd need to put some trimmers also around that

Channel: Robin de Jongh

Views: 48,656

Keywords: Cathedral ceiling, Cathedral roof, Vaulted ceiling, Vaulted roof, gable frame, home extension how-to, how to extend your home, how to support a vaulted roof, ridge beam, robin de jongh, single storey home extension, steel gable frame, uk home extension, vaulted roof structure, vaulted roof support, cathedral ceiling structure, cathedral roof support, how to support a cathedral ceiling, how to support a roof

Id: BtsZk0UR2EI

Length: 9min 42sec (582 seconds)

Published: Thu May 26 2022