Jml Posted March 17, 2018 Share Posted March 17, 2018 Our bungalow was modified in various ways by previous owner. Our lounge, which will become our new entrance hall, has an open void above to the roof, above the ceiling. Having spent a few hours crawling around and pulling back the fluffy insulation, I have found that the there are two joist present, 2 x 4” ceing joists and 2 x8” floor joists for a boarded out central area ( I lifted a small portion to confirm). These joists run in the same direction as the roof ridge line. My understanding was that both ceiling and floor joists are structural as they stop the ouside walls from spreading under the roof load, but that is when they are at right angles to the roof ridge line. As my ceiling and floor joists run parallel with the roof ridge, are they structural? Also what stops the roof weight from pushing the outside walls outwards? Link to comment Share on other sites More sharing options...
PeterW Posted March 17, 2018 Share Posted March 17, 2018 Have a look above your head and see if there are purlins in the roof - will probably be 3x10 or 4x8 timbers or steels running parallel to the ridge. Also check the rafter depth - usual giveaway that it’s a cut roof not a trussed roof is if they are over 75mm deep - and you may find at purlin level there are additional timbers joining both sides of the roof like an “A” and these stringers or collar ties hold the roof together. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted March 17, 2018 Share Posted March 17, 2018 (edited) Sounds a bit odd. You need to know how the roof is braced have you any pictures of the internal structure. (Cross posted with Peterw) Edited March 17, 2018 by MikeSharp01 Cross post Link to comment Share on other sites More sharing options...
Jml Posted March 17, 2018 Author Share Posted March 17, 2018 (edited) 33 minutes ago, PeterW said: Have a look above your head and see if there are purlins in the roof - will probably be 3x10 or 4x8 timbers or steels running parallel to the ridge. Also check the rafter depth - usual giveaway that it’s a cut roof not a trussed roof is if they are over 75mm deep - and you may find at purlin level there are additional timbers joining both sides of the roof like an “A” and these stringers or collar ties hold the roof together. Purlins mid height 3x 6” each side, ridge 1.5 x 7”, rafters 4x 2”. No collar ties, this is only half the old roof length though as a roof with dormer was created in the other half. Joists run to a downstairs structural wall in middle of original bungalow, I think. 31 minutes ago, MikeSharp01 said: Sounds a bit odd. You need to know how the roof is braced have you any pictures of the internal structure. (Cross posted with Peterw) Pictures attached, wall shown was original end of bungalow, a side extension was added hence the door, floor joists in that area do run at 90 deg. to roof ridge! Edited March 17, 2018 by Jml Link to comment Share on other sites More sharing options...
MikeSharp01 Posted March 17, 2018 Share Posted March 17, 2018 Ah so looks like the roof is supported by the ridge beam and the purlins each of which are supported on structural walls at the ends so the loads on the sidewalls are low and spread is not likely to be an issue. If the rafters run to those structural walls then that explains the issue with the rafter runs. Those walls are key to the structure so treat with care. Get structural engineer to check it all over once you have a plan and before you impliment it. Link to comment Share on other sites More sharing options...
Jml Posted March 17, 2018 Author Share Posted March 17, 2018 16 minutes ago, MikeSharp01 said: Ah so looks like the roof is supported by the ridge beam and the purlins each of which are supported on structural walls at the ends so the loads on the sidewalls are low and spread is not likely to be an issue. If the rafters run to those structural walls then that explains the issue with the rafter runs. Those walls are key to the structure so treat with care. Get structural engineer to check it all over once you have a plan and before you impliment it. So that would suggest the floor and ceiling joists are not structural? Link to comment Share on other sites More sharing options...
MikeSharp01 Posted March 17, 2018 Share Posted March 17, 2018 26 minutes ago, Jml said: So that would suggest the floor and ceiling joists are not structural? It looks that way but you need to get an SE to look at your plans, there may well be something we have missed. Link to comment Share on other sites More sharing options...
Jml Posted March 17, 2018 Author Share Posted March 17, 2018 11 minutes ago, MikeSharp01 said: It looks that way but you need to get an SE to look at your plans, there may well be something we have missed. Many thanks. Was definitely getting SE, was just surprised joists running counter to what expected. We hope to take out at least half of joists to make open hallway, with skylight in roof, it will certainly be cheaper if not structural. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted March 17, 2018 Share Posted March 17, 2018 4 hours ago, Jml said: We hope to take out at least half of joists to make open hallway, with skylight in roof, it will certainly be cheaper if not structural. Might be able to take half out by doubling up those that are left. Link to comment Share on other sites More sharing options...
PeterW Posted March 17, 2018 Share Posted March 17, 2018 If nothing going above as it’s full height to the roof then you should be able to take then lot out. Purlins will be holding the walls but just watch for joists going through the structural walls and it leaving lots of holes or joists hanging on to nothing on the other side ! Link to comment Share on other sites More sharing options...
Jml Posted March 18, 2018 Author Share Posted March 18, 2018 15 hours ago, MikeSharp01 said: Might be able to take half out by doubling up those that are left. 14 hours ago, PeterW said: If nothing going above as it’s full height to the roof then you should be able to take then lot out. Purlins will be holding the walls but just watch for joists going through the structural walls and it leaving lots of holes or joists hanging on to nothing on the other side ! Many thanks for thoughts. Still to investigate next bit of roof and floor under dormer room so hopefully that will not throw further spanner in the works. Just realised may have problem with one of floor joists as 2x4 “ support for purlin rests on it, which assume cant just remove, its in wrong place, for design, so hopefully can easily be engineered around. Link to comment Share on other sites More sharing options...
PeterW Posted March 18, 2018 Share Posted March 18, 2018 22 minutes ago, Jml said: as 2x4 “ support for purlin rests on it Errr .... purlin should only be supported at the walls ..!! Have you got a photo..?? Sounds like someone has decided to reinforce a slight bend in a purlin. If you - or SE - think it needs it then the only way is to sister it with another purlin bolted to it. I’d be inclined to bolt 8x2 front and back with M12 coach bolts every 450mm and I doubt it would go anywhere ever again ... Link to comment Share on other sites More sharing options...
Jml Posted March 18, 2018 Author Share Posted March 18, 2018 1 hour ago, PeterW said: Errr .... purlin should only be supported at the walls ..!! Have you got a photo..?? Sounds like someone has decided to reinforce a slight bend in a purlin. If you - or SE - think it needs it then the only way is to sister it with another purlin bolted to it. I’d be inclined to bolt 8x2 front and back with M12 coach bolts every 450mm and I doubt it would go anywhere ever again ... Picture of support, to rhs is outside wall of dormer room. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted March 18, 2018 Share Posted March 18, 2018 So that upright by the green box is very probably, 99.9%, structural as is the one further to the right by the looks of it as they are supporting the Purlin. What is below the green box on the ground floor? Link to comment Share on other sites More sharing options...
RichS Posted March 18, 2018 Share Posted March 18, 2018 Is it V cut and sits under the purlin or is it just nailed to the face, could have been tacked in simply to run those cables up, as it's very close to the wall I wouldn't have thought it would be supporting much but it's hard to tell from the angle of that shot. Link to comment Share on other sites More sharing options...
Jml Posted March 18, 2018 Author Share Posted March 18, 2018 4 hours ago, MikeSharp01 said: So that upright by the green box is very probably, 99.9%, structural as is the one further to the right by the looks of it as they are supporting the Purlin. What is below the green box on the ground floor? Vertical 4x 2 sits on horizontal one directly under green box, this in turn sits on first of 2 x 8 floor joists, upon which flooring rests. Link to comment Share on other sites More sharing options...
Jml Posted March 18, 2018 Author Share Posted March 18, 2018 5 hours ago, RichS said: Is it V cut and sits under the purlin or is it just nailed to the face, could have been tacked in simply to run those cables up, as it's very close to the wall I wouldn't have thought it would be supporting much but it's hard to tell from the angle of that shot. V cut into purlin, see pics hope clearer. Link to comment Share on other sites More sharing options...
RichS Posted March 18, 2018 Share Posted March 18, 2018 In that case it could very well be structural. I assume there is a load bearing wall beneath what it is sat on. Link to comment Share on other sites More sharing options...
Jml Posted March 18, 2018 Author Share Posted March 18, 2018 1 hour ago, RichS said: In that case it could very well be structural. I assume there is a load bearing wall beneath what it is sat on. Many thanks. On 2x8” floor joist which runs between two structural walls. Link to comment Share on other sites More sharing options...
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