Bracing a Joist for new Stairs

[Panmure]

HI. I'm renovating a house and need to put a new stairwell in going from ground floor to the first floor. I need to strengthen the joist which the stair will lean on. What's the best way to do this? (a little detail: I'm actually re-opening an old stairwell so there is already a trimming joist. The joist I need to strength is the one running across the room - which the trimmer rests on).

Noggins alone won't be enough so I'm planning on laying a new second joist alongside the existing one and carriage bolting them together.

Is this a good approach and are there any handy prefab. fixings I should know about?

 

[masona]

Any photo for us to see?

 

[Static]

More info please, spans of joists, size of opening, size of joists etc etc sketch/photos help

 

[Panmure]

Hi Guys,

Thanks very much for your help. I realised that there was too much info to just post pics so I've actually created a site! Here's the URL:-


http://d.1asphost.com/Panmure/Housepics/ (ignore the word 'roof' at the top)

It's not that complex though

My plan is to put a sister joist on the West side of The Joist. The new joist is (7.5 x 15 x 360cm) will run the entire length of the span and be seated in the wall at either end. I'll then bolt this to the joist that need to be strengthened (the one that carried the trimmer for the floating floor and will have the staircase leaning on it). To do this I'll remove the existing partial sister - which is scrappier that it looks in the pics - it's part of an old doorframe.


Assuming this is feasible, my questions are:
What's the best way to join the joists? What size/type of carriage bolts and washers should I use.
Any clever fixings?
My new joist is 360cm and my span is 350cm - will 5cm either end be enough for the sheer, or do I need some clever hanger types thing. Any idea which?

Many thanks for your help!

 

[Static]

Ok first i would check that your proposed stairs fit. Are you going for a spiral stairs? As i think you may have headroom issues with the sizes you show.

Bolting an additional joist beside the old one is correct, use M10 bolts at 90cm staggered centres. The new joist should be given the same bearing the old one has (probably about 10cm) each end.

I would remove the old piece of door frame.

 

[Panmure]

Thanks a lot!

I've put the joist loosely in place and it doesn't look like there's going to be enough baring on the walls - about 4cm each end

So:
Do I write this off as a newbie mistake and just buy longer joists (what baring is ideally reccomended)
Or, am I as well off using a kind of joist hanger?

(I'm having to make new holes in an old solid stone wall so nothing is standard. Not having to cut stone seems quiet attractive).

Thanks

 

[Static]

Well, minimum bearing length is 40mm so your spot on.. just. Building the joist into the wall is the best way to proceed