Joist hanger or let joist sit on block

monomer

Hi,
I was wondering which method is better.

Let brick layer leave gaps in blocks and put the joists in that way. 400 centres 175x50's c24. 3.6m clear span.

Or

Buy some decent (Cullen/Simpson) joist hangers, let the bricklayer put them in and put the joists on them.

Anybody got strong opinions on one method over the other ? Which has biggest disadvantages ?

Thanks
I.

sydthebeat

assuming you are building a cavity wall.....

absolutly DO NOT build the joists into the blockwork.

First and foremost its destroys your air tightness continuity

AND it puts vulnerable timberwork closer to the dew point in the wall, which is bad.

Gumbo

I like seeing hangers being used as my preference.

cork2

Its beginning to seem like building in is a thing of the past, if you're going for airtightness hang the joists. Build your block work to the height of the top of the joist and then bring in the carpenter to joist it. DO NOT let the mason put in hangers and DO NOT let the mason leave out gaps if you're building them into the wall. It would just be a recipe for disaster. If a carpenter if joisting the house he spaces the joists not the mason.

monomer

cork2 : its not easy to get good advise so any appreciated.

are you saying once at joist level, let the carpenter install/secure the joist hangers ? and then let the mason continue the job ?

so far one structural engineer has told me to get the mason to leave gaps, not to use joist hangers.
and one carpenter said, "do either", no difference to me.

!

cork2

monomer wrote: »

cork2 : its not easy to get good advise so any appreciated.

are you saying once at joist level, let the carpenter install/secure the joist hangers ? and then let the mason continue the job ?

so far one structural engineer has told me to get the mason to leave gaps, not to use joist hangers.
and one carpenter said, "do either", no difference to me.

!

I'm a carpenter, I'm just giving my opinion. If you have a structural engineer telling you this, then if he's signing off it's his call. But as a carpenter I wouldn't be a bit impressed to see gaps left out in the blockwork. Joists must be spaced out centre to centre of the joist so the sheets of ply and plasterboard land in the correct place and if the mason sets them out wrong your plywood and plasterboard will have to be cut to suit what you're left with incurring huge waste. technically a mason can do it, I've just never in my experience met one I'd trust to do it.
Hangers also work and seem to be the way of the future. Same story but you need to be more specific again. If your hangers are in the wrong place you're back to cutting and waste again. If the carpenter fits the joists or hangers he will also fit the plywood, therefore will set out the joists to make his plywood fit. I agree with your carpenter from his point of view it makes no great difference to him apart from building in is way faster. From your point of view get a price for hangers, they're expensive, also check their specifications the ones I've used have to be bolted to the wall aswell as hung. Is this a floor or a roof or what?? Also is airtightness an issue here?

Calahonda52

Question for Cork2 as a carpenter, if I may.

What about the version where a wall plate is bolted to the wall and then fit the hangers on that?

It has the advantage that you can airtight behind it with either render or membrane.

I have seen it done in a few block built houses so just wonder what you think.
Thanks

cork2

Calahonda52 wrote: »

Question for Cork2 as a carpenter, if I may.

What about the version where a wall plate is bolted to the wall and then fit the hangers on that?

It has the advantage that you can airtight behind it with either render or membrane.

I have seen it done in a few block built houses so just wonder what you think.
Thanks

I've seen this done twice recently.In my opinion from my point of view towards fitting on site it's actually probably a faster method but I can't see engineers specifying it as a choice method. You're counting a lot on the men on site to put enough bolts in the wallplate and enough twisted nails in the hanger. If the built in hanger has 2 holes it gets 2 bolts but a wallplate every fella will have bolts a different distance apart and the metal in the built in hanger is much stronger. If you know your trades well then there's nothing at all wrong with bolting on wallplates. From an airtightness point you're right it's a very easy detail to continue you airtight layer from upstairs to downstairs without breaking it. Now all the bolts in the wallplate are penetrating the airtight layer but realistically in my opinion the leakage won't be worth talking about!!

Calahonda52

Much obliged for this.

THE DON FANUCCI

cork2 wrote: »

I'm a carpenter, I'm just giving my opinion. If you have a structural engineer telling you this, then if he's signing off it's his call. But as a carpenter I wouldn't be a bit impressed to see gaps left out in the blockwork. Joists must be spaced out centre to centre of the joist so the sheets of ply and plasterboard land in the correct place and if the mason sets them out wrong your plywood and plasterboard will have to be cut to suit what you're left with incurring huge waste. technically a mason can do it, I've just never in my experience met one I'd trust to do it.
Hangers also work and seem to be the way of the future. Same story but you need to be more specific again. If your hangers are in the wrong place you're back to cutting and waste again. If the carpenter fits the joists or hangers he will also fit the plywood, therefore will set out the joists to make his plywood fit. I agree with your carpenter from his point of view it makes no great difference to him apart from building in is way faster. From your point of view get a price for hangers, they're expensive, also check their specifications the ones I've used have to be bolted to the wall aswell as hung. Is this a floor or a roof or what?? Also is airtightness an issue here?

hi Cork2,

I'm going starting a new build soon! Will my roofer be able to do my joists? I'm using timber joists not hollow core slabs. and how do I run my services through the joists such as lighting cables, plumbing, wires ,etc ?? can small holes be drilled for the services to run through my joists.

cork2

THE DON FANUCCI wrote: »

hi Cork2,

I'm going starting a new build soon! Will my roofer be able to do my joists? I'm using timber joists not hollow core slabs. and how do I run my services through the joists such as lighting cables, plumbing, wires ,etc ?? can small holes be drilled for the services to run through my joists.

Hi there, if your roofer is a carpenter then joisting will be no problem to him. Your plumbers and electricians will drill the relevent holes in the joists to run services, it won't be an issue.

THE DON FANUCCI

cork2 wrote: »

Hi there, if your roofer is a carpenter then joisting will be no problem to him. Your plumbers and electricians will drill the relevent holes in the joists to run services, it won't be an issue.

Ok cool. Sounds pretty straight forward. I'm building a fairly standard two storey house nothing big at all. What size joists are standard? 9x2 is it ?
If I go direct labour will my carpenter give me a list of materials to buy, for my joists and roof, etc ?

Gumbo

THE DON FANUCCI wrote: »

hi Cork2,

I'm going starting a new build soon! Will my roofer be able to do my joists? I'm using timber joists not hollow core slabs. and how do I run my services through the joists such as lighting cables, plumbing, wires ,etc ?? can small holes be drilled for the services to run through my joists.

cork2 wrote: »

Hi there, if your roofer is a carpenter then joisting will be no problem to him. Your plumbers and electricians will drill the relevent holes in the joists to run services, it won't be an issue.

You can drill the joists, but only in specific positions and specific distances from the edges etc

There's a limit to the diameter of the hole also so as to not effect the structural properties of the joist.

Homebonds actually give good guidance on these figures. Or the timber span guide may help also.

BryanF

Google I-joists

galwaytt

cork2 wrote: »

Hi there, if your roofer is a carpenter then joisting will be no problem to him. Your plumbers and electricians will drill the relevent holes in the joists to run services, it won't be an issue.

Be very wary of plumbers or electricians going at joisting. No notches. No holes above xx size ( as advised by joist size/load )

BryanF

galwaytt wrote: »

Be very wary of plumbers or electricians going at joisting. No notches. No holes above xx size ( as advised by joist size/load )

Have had plenty of cases That required strengthening of joists due to this - notches should be marked in week 1 of 1st fix and agreed, before notching happens.

ht9zni1gs28crp

another quick tip...before you put the hangers on sand and cement plaster the last two courses of blockwork. Will work wonders for your airtightness.

893bet

I bolted a wall plate to the external walls and used hangers. Personally made sure that there was a bold used every 12 inches or so and that every single hole in the hangers had a twist nail.