MortarThePoint Posted November 12, 2020 Share Posted November 12, 2020 (edited) Does anyone have any advice when it comes to reviewing the roof truss design? We are having attic trusses. Edited November 12, 2020 by MortarThePoint Link to comment Share on other sites More sharing options...
Dave Jones Posted November 12, 2020 Share Posted November 12, 2020 what do you mean ? Link to comment Share on other sites More sharing options...
MortarThePoint Posted November 12, 2020 Author Share Posted November 12, 2020 1 minute ago, Dave Jones said: what do you mean ? Cautionary tails Make sure they've included X in the price You may have forgotten a loft hatch (cough cough) I don't know what it is that I don't know Link to comment Share on other sites More sharing options...
Dave Jones Posted November 12, 2020 Share Posted November 12, 2020 truss company was one of the easier suppliers to deal with I found. You give them the plan they provide you the truss and fixings to make it work to the drawing and calcs they have done for building control. Get the hatch yourself they cheap. 1 Link to comment Share on other sites More sharing options...
MortarThePoint Posted November 12, 2020 Author Share Posted November 12, 2020 1 minute ago, Dave Jones said: truss company was one of the easier suppliers to deal with I found. You give them the plan they provide you the truss and fixings to make it work to the drawing and calcs they have done for building control. It has been very smooth and I've enjoyed working with the designer, but I'm hoping it hasn't been too easy and I've forgotten something. Link to comment Share on other sites More sharing options...
Thorfun Posted November 12, 2020 Share Posted November 12, 2020 26 minutes ago, MortarThePoint said: You may have forgotten a loft hatch (cough cough) thanks for the tip! just checked my roof truss plans and the loft hatches have been accommodated, but I hadn't previously checked so is a great tip. Link to comment Share on other sites More sharing options...
Dave Jones Posted November 12, 2020 Share Posted November 12, 2020 truss centres are normally 600 so plenty of room to fitch a hatch. Link to comment Share on other sites More sharing options...
Mr Punter Posted November 12, 2020 Share Posted November 12, 2020 You can get attic trusses with EasyJoist bottom chords so you can run services through them. You cannot otherwise drill any part of them without written agreement from the designer. 1 1 Link to comment Share on other sites More sharing options...
MortarThePoint Posted November 12, 2020 Author Share Posted November 12, 2020 39 minutes ago, Mr Punter said: You can get attic trusses with EasyJoist bottom chords so you can run services through them. You cannot otherwise drill any part of them without written agreement from the designer. That's worth knowing. I was presuming there was a diameter of hole (e.g. 25mm) that as long as drilled in the middle of the joist was OK Link to comment Share on other sites More sharing options...
markc Posted November 12, 2020 Share Posted November 12, 2020 1 minute ago, MortarThePoint said: That's worth knowing. I was presuming there was a diameter of hole (e.g. 25mm) that as long as drilled in the middle of the joist was OK Bottom cord is in tension so the whole cross section of material is loaded. Central holes are fine on joists and beams subject to bending stresses are fine because the top third (ish) is in compression, lower third in tension and the central area is only keeping the tension and compression areas apart. Link to comment Share on other sites More sharing options...
Oz07 Posted November 12, 2020 Share Posted November 12, 2020 Yes check on the quote what their delivery terms are. We've handballed a full attic off Donaldsons once driver had to wait quite a while! Link to comment Share on other sites More sharing options...
Dave Jones Posted November 12, 2020 Share Posted November 12, 2020 no telehandler on site ? How you getting the roof tiles up ? Link to comment Share on other sites More sharing options...
Mr Punter Posted November 12, 2020 Share Posted November 12, 2020 1 hour ago, Dave Jones said: no telehandler on site ? How you getting the roof tiles up ? Bumpa? Link to comment Share on other sites More sharing options...
Dave Jones Posted November 12, 2020 Share Posted November 12, 2020 bet the tilers will love that treble handling everything. There goes the bill doubled!!! Link to comment Share on other sites More sharing options...
Oz07 Posted November 12, 2020 Share Posted November 12, 2020 I meant trusses handballed off Link to comment Share on other sites More sharing options...
epsilonGreedy Posted November 23, 2020 Share Posted November 23, 2020 To be competitive truss designers spec to minimum industry standards. You could always challenge them and say for an extra £200 which part of the design would you re-spec to the next timber size up. Link to comment Share on other sites More sharing options...
joe90 Posted November 23, 2020 Share Posted November 23, 2020 (edited) As yours are attic trusses, what do you propose to put in your loft?, are the designers aware of what you propose goes up there and worked the loading adequately? If it’s Christmas decorations and empty suitcases it won’t be a problem but 40 years worth of beano comics ? Edited November 23, 2020 by joe90 Link to comment Share on other sites More sharing options...
MortarThePoint Posted November 23, 2020 Author Share Posted November 23, 2020 54 minutes ago, joe90 said: As yours are attic trusses, what do you propose to put in your loft?, are the designers aware of what you propose goes up there and worked the loading adequately? If it’s Christmas decorations and empty suitcases it won’t be a problem but 40 years worth of beano comics ? I kept on seeing the symbol below on almost all the trusses and wasn't sure what it was so asked. It's a water tank and the truss designer has allowed for that load on pretty much all trusses that don't have specified dead/live loads. So as long as 40 years of Beano comics weight less than 230kg I'm OK. 1 Link to comment Share on other sites More sharing options...
MortarThePoint Posted November 23, 2020 Author Share Posted November 23, 2020 4 hours ago, epsilonGreedy said: To be competitive truss designers spec to minimum industry standards. You could always challenge them and say for an extra £200 which part of the design would you re-spec to the next timber size up. I had a similar discussion. The top chords were 197mm and I asked if we should increase them he said it wasn't worth it. I then realised I needed the rafter depth for insulation anyway. Link to comment Share on other sites More sharing options...
Thorfun Posted November 23, 2020 Share Posted November 23, 2020 4 minutes ago, MortarThePoint said: I had a similar discussion. The top chords were 197mm and I asked if we should increase them he said it wasn't worth it. I then realised I needed the rafter depth for insulation anyway. we're having 197mm top chords, I'm just going to fill with insulation (obviously leaving the 50mm gap) and then put PIR on the inside against the chords. I believe that's a pretty standard way of doing it? means don't need to pay for thicker trusses. Link to comment Share on other sites More sharing options...
MortarThePoint Posted November 23, 2020 Author Share Posted November 23, 2020 1 minute ago, Thorfun said: we're having 197mm top chords, I'm just going to fill with insulation (obviously leaving the 50mm gap) and then put PIR on the inside against the chords. I believe that's a pretty standard way of doing it? means don't need to pay for thicker trusses. Good plan. That greatly reduces the top chord cold bridge as well. 1 Link to comment Share on other sites More sharing options...
Russell griffiths Posted November 23, 2020 Share Posted November 23, 2020 Get another design and quote and compare the two. If there attic trusses surely the load would be would be the same for any habitable space. Link to comment Share on other sites More sharing options...
MortarThePoint Posted November 23, 2020 Author Share Posted November 23, 2020 Check that the lowest corner of the truss eave won't clash with your scaffolding. They will come cut off simply even if you intend to add a horizontal cut. That means they extend down further at first. I've just been out in the dark checking I have the height and thankfully I do ?. Could be cut during installation, but that wouldn't be fun. Link to comment Share on other sites More sharing options...
Dave Jones Posted November 23, 2020 Share Posted November 23, 2020 just take the scaff board up if it tight 1 Link to comment Share on other sites More sharing options...
epsilonGreedy Posted November 23, 2020 Share Posted November 23, 2020 2 hours ago, joe90 said: As yours are attic trusses, what do you propose to put in your loft?, are the designers aware of what you propose goes up there and worked the loading adequately? If it’s Christmas decorations and empty suitcases it won’t be a problem but 40 years worth of beano comics ? When discussing loading with my truss designer I expressed my disappoint with the low kg figure and replied "no that is your allowance for floor material weight per m2". He then quoted another larger number for storage load per m2. His final comment was that in practice it is archived paperwork stored in attics that concern him the most. Link to comment Share on other sites More sharing options...
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