Posi Joists - 3 quotes, 3 different variations. Any experience / advice?

[kingandy2nd]

Hi All,

I've just got some quotes in from different suppliers for my first floor joists. Designer spec'd engineering joists, and I've ended up with 3 posi joist quotes and one I beam.

All the companies were given the same spec - 5.1m clear span, attach to existing wall via ledger plate on one side, other side sitting on the masonry.

I've ended up with 3 different specs for the posi joists. They're all within 10% price wise, but I don't know what's best!

The 225mm deep ones seem appealing as it allows be to fit nicely into a single course of blockwork without faffing, and keeping the floor level with the existing floor, so I'm leaning towards one of the top two quotes.

However, I really don't know if 10 joist that a 50% wider are better than 14 joists that are thinner. Nor do I have a view if a hanger is better than the top chord on the ledger plate. Any thoughts?

Also is there much difference between Posi and I joist, apart from the ease of running services? The I joists are 20-25% cheaper...

Thanks
Andy

 

[noseall]

attach to existing wall via ledger plate on one side Nor do I have a view if a hanger is better than the top chord on the ledger plate. Any thoughts?

What's wrong with building in both ends?

Also is there much difference between Posi and I joist, apart from the ease of running services? The I joists are 20-25% cheaper...

We only ever use poi-joists from Trussform. They are an absolute boon and no need for acoustic insulation either.

Running services.....

Cluttered!

• noseall
• 12 Nov 2016

I don't know about running services but these fellas below were 420mm deep with 120mm wide chords. You could have a room in the floor space....

Bigjoist1

• noseall
• 19 Nov 2018

 

[noseall]

The 225mm deep ones seem appealing as it allows be to fit nicely into a single course of blockwork without faffing, and keeping the floor level with the existing floor,

You would always keep the floor levels the same irrespective of joists depth and lose discrepancies via the ceilings. Having the joists the same depth as a block is ok for filling between but you may end up cutting blocks to keep in courses with the extenal brickwork and previous block courses i.e. tie wires and insulation batts etc.

 

[kingandy2nd]

Hi Noseall,

Thanks for the comments and the photos. Those 420s look like absolute beasts!

What's wrong with building in both ends?

The other wall is the existing exterior wall of the property, so building in the joists would be a lot harder work than the ledger plate.

We only ever use poi-joists from Trussform. They are an absolute boon and no need for acoustic insulation either.

The posi joists seem to be more popular than I beams, from what I gather online. I think these suppliers are MiTek ones.

You would always keep the floor levels the same irrespective of joists depth and lose discrepancies via the ceilings. Having the joists the same depth as a block is ok for filling between but you may end up cutting blocks to keep in courses with the extenal brickwork and previous block courses i.e. tie wires and insulation batts etc.

As it stands, I’ve got the courses up to the right point where the 225 joists would nicely fit on top of the course without cutting them to accommodate. I guess with the 254s, I’d actually be better off putting the next course of blocks in, but then using masonry hangers to get the height right - like you say, by having a slightly lower ceiling.

 

[kingandy2nd]

Spoke to the closest supplier to me geographically who gave the 14 joists of 97mm, and moving up to 147mm joists only added £150 plus VAT to the quote overall - so I've instructed them to go with that.

For the sake of an extra 15% in the cost, the extra strength/reduced deflection was worth it. Although I might regret this decision when I'm lugging these extra heavy joists into place

 

[kingandy2nd]

Arrived today...look heavy!

 

[noseall]

heavy!

They are surprisingly light. You shuffle them into position rather than lift them. Piece of cake really.