Moonshine Posted September 27, 2020 Share Posted September 27, 2020 O.k so joist hangers are built into a masonry wall, and a metal plate hooks round the top of the block and gets mortared in. So the hanger hieght is dependant on the lock height. So how do you deal with where the required joist level does not tie in the block level? Do you use 1/3 blocks to level up the joist level or do you select joist heights to match? Or can you put a spacer at the bottom of the hanger to get the right level? Link to comment Share on other sites More sharing options...
Declan52 Posted September 27, 2020 Share Posted September 27, 2020 You use bricks to get you to height if that suits better. Then a packer if needed under the hanger. Then it's built over with whatever will bring it back into coursing. 1 Link to comment Share on other sites More sharing options...
Moonshine Posted September 27, 2020 Author Share Posted September 27, 2020 32 minutes ago, Declan52 said: You use bricks to get you to height if that suits better. Then a packer if needed under the hanger. Then it's built over with whatever will bring it back into coursing. Thanks, sounds like it can be sorted during the build once block and joist depths are know rather than at the design stage Link to comment Share on other sites More sharing options...
Iceverge Posted September 27, 2020 Share Posted September 27, 2020 Consider bolting a ledger plate to the wall and then nailing your joist hangers onto it. Much easier to achieve good air-tightness and achieve a level first floor. As per the excellent green building store videos. 2 1 Link to comment Share on other sites More sharing options...
Russell griffiths Posted September 27, 2020 Share Posted September 27, 2020 It has a lot to do with the gauge of the block work, you should build a STOREY POLE this is a piece of timber 50x50 that will have height marks on it, it could have a mark for top of windows, top of doors, first floor height and so on, the brickies can use this to adjust their block height up or down a bit to hit the design height, over 10-12 courses of blocks gaining 1 mm per course will grow the building by 12 mm plus a brick course you can juggle things a lot. All down to good planning. Or as above just run a ledger board around the walls to simplify air tightness. 4 Link to comment Share on other sites More sharing options...
Moonshine Posted October 3, 2020 Author Share Posted October 3, 2020 Looking at the options and my build I think that I am going to use a ledger board with top fix hangers with I joists. The air tightness is a factor but also the build progress. My house has a split level so the height of joists on ground floor aren't consistent so less head scratching for the brickies / error trying to build in the joists. My thoughts are that the hangers could be pre fixed at the required centres on the ground then lifted and fixed into place. The question I have is when do the ledger board get fitted? Surely the blocks need to be a certain height above and mortar set before drilling into wall? Or could a 2 storey external masonry wall be built without the joist being fitted? Link to comment Share on other sites More sharing options...
tonyshouse Posted October 3, 2020 Share Posted October 3, 2020 Build them in and use a ‘tony tray’ to deal with the air tightness. Link to comment Share on other sites More sharing options...
joe90 Posted October 3, 2020 Share Posted October 3, 2020 I too favour a ledger board, does not matter about blockwork then. Easier to parge the wall before fitting the board to achieve airtightness as well and easier to get all joists/ibeams level. Link to comment Share on other sites More sharing options...
Oz07 Posted October 3, 2020 Share Posted October 3, 2020 Didn't we discuss previously deflection is more likely with a ledger because they're not a tight fit on the ends and this increases bounce? One negative to that... I'd think your ok putting a ledger on once 2 or 3 courses above where you need to be, at worst built overhand from the scaffold outside the building Link to comment Share on other sites More sharing options...
Moonshine Posted October 6, 2020 Author Share Posted October 6, 2020 (edited) @Oz07 but would this not be the case if it was going into a standard joist at 90 degrees? Is the standard way to fit the ledger board to the wall (as per the video) drilling a load of holes into the block work (~75mm deep) and then set the threads in expoxy resin, wait for that to go off then bolt it? Any idea on what thickness of thread and spacing's, would it need to be signed off / designed by a structural engineer? The thought of how to practically fix the ledge board, while at a height trying to keep it level and drilling a load of holes in it doesn't sound like great fun, and insight in how to make the installation easier? Edited October 6, 2020 by Moonshine Link to comment Share on other sites More sharing options...
PeterW Posted October 6, 2020 Share Posted October 6, 2020 Last one I fitted we used concrete screws to hold it in place and then drilled 600 centres at 50mm staggered along the centre line starting 150mm from the end, then inserted the Fischer resin capsules and stainless pins. Waited til it went off then nipped them tight. It’s still there and has a lot of weight on it so it must work ..!! 2 Link to comment Share on other sites More sharing options...
Oz07 Posted October 7, 2020 Share Posted October 7, 2020 I don't understand the science but awhile ago there was a discussion with regards pozis As i remember if built in to blockwork the deflection was less compared to on hangers/top chord on top of ledger. It was to do with the end of the joist not being tight up to the ledger and this gives it room to move. I think built in the friction of the blockwork stops this. Can anyone link/remember the discussion? Link to comment Share on other sites More sharing options...
Moonshine Posted October 7, 2020 Author Share Posted October 7, 2020 15 minutes ago, Oz07 said: I don't understand the science but awhile ago there was a discussion with regards pozis I am looking to use I joists if it makes any difference Link to comment Share on other sites More sharing options...
ZacP Posted October 7, 2020 Share Posted October 7, 2020 Also, would this change if you reduced the centres from 600 to 400? Keeping the spec of joists the same? Hopefully this might negate the extra flex that seems inevitable with a less supported junction with the wall. I can also see the benefit of using a ledger in terms of ease of use and therefore cost saving. Link to comment Share on other sites More sharing options...
PeterW Posted October 7, 2020 Share Posted October 7, 2020 You should really pack the sides of the I-Joists with OSB when fitting them into hangers. You could go round after and put wedges behind the joist, or make sure they are tight fitted when they are installed with no slack or slop in the hangers. It is about attention to detail and speed of installation. A normal joinery crew will cut to approx size to allow the joist to slot in easily. You want them tight so it may be a case of cut and trim 2 or 3 times to get that. Also worth using Z clips and noggins even with ledger boards to stop the joists twisting in the hangers. 1 Link to comment Share on other sites More sharing options...
Moonshine Posted October 8, 2020 Author Share Posted October 8, 2020 @PeterW that is some good advice, and I can see myself going round and putting wedges in. You mention that joists are cut to size. Is it normal to order just over size length and cut down on site? Link to comment Share on other sites More sharing options...
PeterW Posted October 8, 2020 Share Posted October 8, 2020 I-Joists such as JJI etc with the timber flange are normally standard lengths and can be cut on site. Metal web joists are not as flexible and normally come as a measured item. Link to comment Share on other sites More sharing options...
Moonshine Posted October 8, 2020 Author Share Posted October 8, 2020 Good to know , I was a bit worried about having to get bang on measurements but cutting on site may be more time consuming but means a good fit can be achieved Link to comment Share on other sites More sharing options...
Vijay Posted October 8, 2020 Share Posted October 8, 2020 13 hours ago, Oz07 said: I don't understand the science but awhile ago there was a discussion with regards pozis As i remember if built in to blockwork the deflection was less compared to on hangers/top chord on top of ledger. It was to do with the end of the joist not being tight up to the ledger and this gives it room to move. I think built in the friction of the blockwork stops this. Can anyone link/remember the discussion? A supplier said the deflection was worse when the joists were through the blockwork for me and better with hangers Link to comment Share on other sites More sharing options...
joe90 Posted October 8, 2020 Share Posted October 8, 2020 12 hours ago, ZacP said: reduced the centres from 600 to 400 this is what we did as I hate bouncy floors and it worked well. Link to comment Share on other sites More sharing options...
Moonshine Posted October 14, 2020 Author Share Posted October 14, 2020 On site today and saw these i-joists built into an external wall, a fair amount of gaps around them. Link to comment Share on other sites More sharing options...
joe90 Posted October 14, 2020 Share Posted October 14, 2020 (edited) Flexible mastic might be your friend here to help with air tightness. The timber will shrink a little so any gap filler must be able to flex with it. Are you going to parge the walls?, wet plaster? You need to get parging done on the blockwork between joists before the ceiling goes up . I did mine before the upper floor went down as well,. Edited October 14, 2020 by joe90 Link to comment Share on other sites More sharing options...
Moonshine Posted October 14, 2020 Author Share Posted October 14, 2020 @joe90 this isn't my build but I was on the site of a local medium volume builder 1 Link to comment Share on other sites More sharing options...
PeterW Posted October 14, 2020 Share Posted October 14, 2020 Looks about right for a spec builder - that one won’t be air tested ... Link to comment Share on other sites More sharing options...
Russell griffiths Posted October 14, 2020 Share Posted October 14, 2020 That’s a standard shit job, you should be aiming for 100% better than that. 1 1 Link to comment Share on other sites More sharing options...
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