ToughButterCup Posted July 23, 2018 Share Posted July 23, 2018 Roof on (ish) need to think about the flat roof and first floor now. Each is supported by metal web joists, POSIs in our case : MiTek. In measuring their length to assemble an order, how accurate do the measurements have to be? To within 5 mm? Its just that our wall is pretty wavy if you know what I mean (Don't ask, it just is ?) Link to comment Share on other sites More sharing options...
joe90 Posted July 23, 2018 Share Posted July 23, 2018 I would tend to order slightly over length, you can always trim to fit exactly, you can’t add really. Link to comment Share on other sites More sharing options...
Alexphd1 Posted July 23, 2018 Share Posted July 23, 2018 How are you hanging them. We where hanging on the top chord so ordered this long while we could pack out bottom chord/closer for our wavy walls. Link to comment Share on other sites More sharing options...
PeterW Posted July 23, 2018 Share Posted July 23, 2018 46 minutes ago, recoveringacademic said: Roof on (ish) need to think about the flat roof and first floor now. Each is supported by metal web joists, POSIs in our case : MiTek. In measuring their length to assemble an order, how accurate do the measurements have to be? To within 5 mm? Its just that our wall is pretty wavy if you know what I mean (Don't ask, it just is ?) The supplier measures ... they are non-standard units if they are metal web so the supplier should come out and do a site survey and then design to that - they then come with a numbered fitting schedule and a design. Link to comment Share on other sites More sharing options...
ToughButterCup Posted July 23, 2018 Author Share Posted July 23, 2018 19 minutes ago, PeterW said: The supplier measures ... they are non-standard units if they are metal web so the supplier should come out and do a site survey and then design to that - they then come with a numbered fitting schedule and a design. Right then Pete. I'll tell 'em..... " My mate Pete, missin' a few teeth, needs a new nose and comes up from the Smoke (know what I mean; nod's as good as wink to a blind self-builder) , says you have ter come aert 'n measure up like.... " That'll put the wind up them. Up to now (Minera and Cheshire Floor Joists) have said - very politely - to measure it myself. Hence the concern about accuracy 1 Link to comment Share on other sites More sharing options...
Alexphd1 Posted July 23, 2018 Share Posted July 23, 2018 We got the a similar reply measure it yourself and to be honest it worked well. Link to comment Share on other sites More sharing options...
PeterW Posted July 23, 2018 Share Posted July 23, 2018 Mine won’t let me ... summat about me having an elastic tape measure ..... How are you fitting them ..? Face fix to a ring beam..? Link to comment Share on other sites More sharing options...
ToughButterCup Posted July 23, 2018 Author Share Posted July 23, 2018 1 minute ago, PeterW said: [...] How are you fitting them ..? Face fix to a ring beam..? Yes. In the words of the architect '.... installed to Mi-Tek standard details and instructions ... ' whatever that means. I have the MiTek Posi Joist manual (PS8 TR26 - whassat?) and frankly it might as well be written in Aramaic..... But, I'll get there. Link to comment Share on other sites More sharing options...
nod Posted July 23, 2018 Share Posted July 23, 2018 6 hours ago, recoveringacademic said: Roof on (ish) need to think about the flat roof and first floor now. Each is supported by metal web joists, POSIs in our case : MiTek. In measuring their length to assemble an order, how accurate do the measurements have to be? To within 5 mm? Its just that our wall is pretty wavy if you know what I mean (Don't ask, it just is ?) Add 200 mil on and cut to size on site Much easier If you send your drawing to Pasquils at Chorley they normally offer to do this Link to comment Share on other sites More sharing options...
mvincentd Posted July 23, 2018 Share Posted July 23, 2018 Crendon did the measuring themselves on mine but it didnt prove entirely trustworthy so i'm glad i went for trimmable ends. Try to make all trims from the same end so your webs remain in line. On that note also try to discourage them from introducing a range of supporting methods, as that will also throw off the webs and potentially close the continuous service channels that are such a benefit. Link to comment Share on other sites More sharing options...
ToughButterCup Posted July 24, 2018 Author Share Posted July 24, 2018 7 hours ago, mvincentd said: Crendon did the measuring themselves on mine but it didnt prove entirely trustworthy so i'm glad i went for trimmable ends. Try to make all trims from the same end so your webs remain in line. On that note also try to discourage them from introducing a range of supporting methods, as that will also throw off the webs and potentially close the continuous service channels that are such a benefit. Thanks everyone. @mvincentd, what does ' ... a range of supporting methods ... ' mean? The point you make about continuous service channels is important to us because the POSI spec allows only a couple of mm clearance for the MVHR piping..... Link to comment Share on other sites More sharing options...
mvincentd Posted July 24, 2018 Share Posted July 24, 2018 33 minutes ago, recoveringacademic said: @mvincentd, what does ' ... a range of supporting methods ... ' mean? Imagine a blockwork inner leaf broken by a steel goalpost structure surrounding the opening for sliding doors. So mines made a tad awkward by faceted wall faces but it still demonstrates.....top pic shows combination of pozi bearing onto blockwork and alongside pozi in hangers on timber packer in the steel. (Just for fun add a steel coming off the goalpost parallel with poi's). The different bearing approach has altered the length of pozi and therefore shifted the webs. You then get picture 2 for your mvhr! For me this was my best positional option for the hole....nobody could calculate it in advance of placing the pozi's, ruling out a neat plasma cut circle in factory so it came down to an angle grinder in-situ. Picture 3 shows another instance of different build methods meeting causing a change in pozi hanging method (rc wall continued as blockwork). Link to comment Share on other sites More sharing options...
ToughButterCup Posted July 24, 2018 Author Share Posted July 24, 2018 Ahhhh..... nightmare for you. Ours is an order of magnitude simpler. Thanks for the explanation: as usual, the Devil is in the detail. Link to comment Share on other sites More sharing options...
PeterW Posted July 24, 2018 Share Posted July 24, 2018 Sorry guys but I disagree about trimming these on site... let me explain why...!! The structural strength in the floor is made up of three components, the joists, the deck and the strongbacks. The strongbacks are either one or two large section timbers that run down the centre of the joists or at pre-determined points through the webs. They attach to blocks that are fitted between the upper and lower chords so they have to be in line or the strongback will not fit...! It must be nailed to the blocks as it stops the twisting moment in the floor joists and creates a "strong back" through the middle of the webs. You also need to work a method of adding the strongback into the joists as 6x2 doesn't tend to bend round corners nicely... Link to comment Share on other sites More sharing options...
mvincentd Posted July 24, 2018 Share Posted July 24, 2018 16 minutes ago, PeterW said: they have to be in line or the strongback will not fit...! It must be nailed to the blocks If trimming is restricted to one consistent end only then the block line will not alter. Link to comment Share on other sites More sharing options...
joe90 Posted July 24, 2018 Share Posted July 24, 2018 This is one reason I prefer finnjoists (osb webb) they can be cut to any length as long as they are specced for the longest length and cutting holes in the Webb is easy (as long as they are in the right place and right dimensions. 1 Link to comment Share on other sites More sharing options...
PeterW Posted July 24, 2018 Share Posted July 24, 2018 11 minutes ago, mvincentd said: If trimming is restricted to one consistent end only then the block line will not alter. That’s ok as long as the walls are consistent ... or one is flat and the other wavers from this one. I think @recoveringacademic has variation in both walls Link to comment Share on other sites More sharing options...
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