October 28, 20187 yr Wondering on the collective opinion, what is the better way to support posi-joists on internal blockwork walls? The two options, as far as I can see -Bear the bottom chord directly on the block work or -Use a JHM type hanger Any structural advantages to either method? Will be trying to minimise any movement/deflection Bearing directly onto the block work is easier and cheaper and length of joists less critical Using hangers feels the more superior way to do it but I'm not sure why! Just to add the block work walls will continue up another story so there will be plenty of weight bearing down
October 28, 20187 yr I would say built in as well the only down side is the length of joist, will you be able to handle a full length that goes from outer wall to outer wall will it be too heavy or lack of space to manage our roof timbers are 11m but only weighs 45kg. Little things to think about.
October 28, 20187 yr Ours were built in, this allowed the joists to be a little over length and overlap each other but enabled them to be “tight” into the hangers on the outside walls.
October 28, 20187 yr Author 3 minutes ago, Russell griffiths said: I would say built in as well the only down side is the length of joist, will you be able to handle a full length that goes from outer wall to outer wall The internal block walls are not intermediary supports. They are supporting the ends of the joists
October 28, 20187 yr OK. Make sure you specify the max deflection must not exceed 8mm or 0.002 x span. The standard is 12mm which can feel a bit bouncy. 2 stairs?
October 28, 20187 yr Author @Mr Punter thanks will do Yep 2 stairs. Set to the right services bedroom with full height vaulted ceiling only. Rest of the property is under a different pitch roof that has to be a bat roost. ?
November 7, 20187 yr so glad @willbish asked this question. Does rigidity play a part in this at all? Also, in an ICF situation if you were building into the wall after the first pour, I assume you'd have to protect the end of the joists with something, even if only a layer of polythene around those ends?
November 7, 20187 yr Author @Big Neil There are various methods for ICF, have you had a look at the Ledger Connector from Simpson Strong tie. I will be using this method. https://www.strongtie.co.uk/products/detail/ledger-connector/346
November 7, 20187 yr Thanks Mr Bish, i'll take a proper look later but i've got the details up now. I figured it might just need a metal/plastic sleeve to protect the wood from the concrete, if it was just to be sat on top of the wall prior to the second pour.
November 7, 20187 yr was thinking something like this https://www.roofingsuperstore.co.uk/product/manthorpe-g912-joist-seal-48mm-x-100mm-translucent-white.html?gclid=CjwKCAiAt4rfBRBKEiwAC678KcjBxveTrh3hG-s_f4hNIHcnxh49q4Yn9ls9Y3noA64_uHRT0pzX1hoC6F8QAvD_BwE
November 8, 20187 yr Author @Big Neil with ICF the walls will be propped, usually from the inside, to ensure alignment during concrete placement. If you are intending to cast your joist ends into the concrete core all your joists will need to be propped as well. This could get very crowded! The other issue is ensuring no concrete leaks where your joists penetrate the inner leaf of the ICF. I've only seen a handful of ICF builds, they all have fixed joists after the concrete has been poured.
November 25, 20187 yr On 08/11/2018 at 07:06, willbish said: If you are intending to cast your joist ends into the concrete core all your joists will need to be propped as well. This could get very crowded! Was thinking of placing them after the first pour which would be to joist bearing height, then the props for the first part could be taken away anyway. Metal end caps for the end of the joists - jobs-a-goodun.
November 25, 20187 yr 12 minutes ago, Big Neil said: Was thinking of placing them after the first pour which would be to joist bearing height, then the props for the first part could be taken away anyway. Metal end caps for the end of the joists - jobs-a-goodun. You would need to insure your concrete pour was accurate to within 3-5 mm over the length of the wall, or your joists would all be out of level, you would then need to cut every block you put on next to accommodate the joist in the way. I really don’t see what benefit this method would have over the standard fixing method of a pole plate bolted to the wall and joist hangers. The canadians and the yanks have been doing it like this for years, can’t see any reason to change it.
November 25, 20187 yr fair point. Has anyone got any pictures of the method you describe in use. Just can't picture how it works in my head
November 25, 20187 yr Look up FOX blocks on YouTube, they seam to have more vids than anybody else. You can do it a few ways you put your pole plate,ledger board, rim joist, call it what you like, in position, screwed to the wall with temporary fixings, mark out your joist layout, work out where your fixing bolts go and drill holes in pole plate, remove pole plate and cut a large hole in your icf in the location of the bolts, fit a membrane of some description to the back of the timber, put timber back up with bolts projecting into the holes you cut, when you pour your concrete it will flow into the holes you cut and surround the bolts, it will end up with concrete pads projecting out to the back of the timber adding the support you wouldn’t get from the insulation layer. I will be doing mine in a months time, I will try and remember to take a few pics.
November 27, 20187 yr Thanks for all the answers. I'll look at FOX blocks later. Unlikely i'll be able to get down your way before Christmas, but thanks very much for the offer. Just trying to arrange a site visit for a thermomur build somewhere up near me in Manc-land at the moment, so should be interesting to see.
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