Joining joist question

[liamruairi]

Doing my loft extension; total house width span is around 6400. I have a steel beam in the middle and joists (3m and 3.6m joists) will meet in the middle resting on the beam for support. Is it ok to simply m10 coach bolt the joists on the beam together where they overlap slightly? As opposed to a joist running the length of the beam with joist hangers on it? The beam offers the structural support.
Secondly, a possible alternative that has arisen is to feed ends of joists into the beam web. However there’s nothing to fix them there apart from the web itself (they will be full of noggins etc so won’t move about). A timber bolted to the web isn’t possible now as beam is in place and there aren’t any bolt holes in it and I already broke 3 bits trying to drill into it!! Just wondering if there was an alternative or if bc would accept that? Initially the plan didn’t allow for that but we’ve found that in situ it may be possible so just thinking about it. Thanks!

 

[garyo]

If the beam's already in place then isn't it too late to decide whether to feed the joist ends in to the web, versus resting them on top?

Personally I'd prefer to have fixed them in to the web somehow, as it's a more efficient use of head height rather than risking the beam having a downstand in the room below (unless you're lucky with the position of dividing walls)

 

[liamruairi]

If the beam's already in place then isn't it too late to decide whether to feed the joist ends in to the web, versus resting them on top?

Personally I'd prefer to have fixed them in to the web somehow, as it's a more efficient use of head height rather than risking the beam having a downstand in the room below (unless you're lucky with the position of dividing walls)

The beam and joists are unconnected to the floor / ceiling below as the beam is resting on the front wall of the house and a brick load bearing wall at other end

 

[blup]

I'm no expert but in principle would it not be the same as laying the joist on a wall plate, assuming the joist size/strength is suitable for the span in question?

Blup

 

[garyo]

The beam and joists are unconnected to the floor / ceiling below as the beam is resting on the front wall of the house and a brick load bearing wall at other end

What are the joists - are they the floor joists for the loft room?

 

[liamruairi]

The beam and joists are unconnected to the floor / ceiling below as the beam is resting on the front wall of the house and a brick load bearing wall at other end

What are the joists - are they the floor joists for the loft room?

Yes floor joists in loft conversion

 

[tony1851]

@op. what is the section size of the beam?

 

[Ian H]

If you put them into the web your bedrooms will be 8" lower and your loft 8" higher.

You can drill the RSJ, you need to drill slow and plenty of lube. Make a small hole first.

 

[liamruairi]

If you put them into the web your bedrooms will be 8" lower and your loft 8" higher.

You can drill the RSJ, you need to drill slow and plenty of lube. Make a small hole first.

Right... going to rethink drilling the beam. What kind of lube? M16 bolts to join wood to beam?

 

[liamruairi]

If you put them into the web your bedrooms will be 8" lower and your loft 8" higher.

You can drill the RSJ, you need to drill slow and plenty of lube. Make a small hole first.

@op. what is the section size of the beam?

Dunno will crawl up tonight and have a look think it’s 175 off top of head

 

[Ian H]

WD40 would do it.

 

[tony1851]

WD40 would do it.

I was thinking KY myself.........

 

[John D v2.0]

I usually use that 3 in 1 oil for drilling things as it's sticky enough to hang around long enough to drill a few holes.

 

[garyo]

I use anything that I have hanging around and it works okay (WD, GT85, 3in1, etc). The main thing is to make sure you don't overheat/overwork the bit and getting the rotation speed right for the bit size. Having the right oil presumably gives you much wider margins to work within. For a UB web I'd drill a 1mm pilot, then something like a 5mm, then the final 12mm.

 

[liamruairi]

So the reason I thought it wasn’t possible is because I tried before with crap bits and the literally just shrank before my eyes into nothing without leaving so much as a scratch. Cue quality bits and they went through it making a test hole like a hot knife through butter. So this is now a possibility; saving me around 6’ head height. Just need to ok it with BC as it’s not in the plan. The web is 175 and the joists are 200 so will need new timbers for it. Am guessing 600mm spacing m12 bolts would suffice?