Two sets of roof joists - new hatch opening

[dan_cup]

Morning folks,

So as you can see the loft area in our 30s semi has been done out many years ago, they added 6x2 joists in addition to the original 3x1.5s. to the left of the picture is my existing loft opening which opens onto the handing, but the ladder drop is being impeded by the bathroom door, so we want to have the loft hatch on the opposite side of the landing, opening the opposite way. it will also be 1200x700.

The joists run in the adjacent direction so I can't just cut one joist and fit the hatch in-between, I need to run right to left as seen in the picture. I will likely need to cut 3 joists (or in my case 6, 3 big and 3 small!)

question is how to support all this while making the cuts.

where the hoover pipe is, there is a brick wall running right to left supporting the joists. they run out the the wall plate at the top of the picture, which is off the stair well, this span is 3m.

Can I support the 6x2 lengths by running a lump of wood across all the joists, and then support from underneath, on the landing the 3x1.5s? or am I jumping the gun thinking its ok to cut so many joists?

I could probably use the existing opening, turn the ladders through 180deg, but id still want to have a larger opening.

cheers

 

[Wayners]

Make T bars... Dead man to support ceiling under.
Then screw the T bars to ceiling so they stay put.

Sister joists if you think it's required.
Watch this 4 mins in

You can PVA the laths to strengthen plaster while you're at it and floor is up

 

[Dereekoo]

So when you have cut all the joists and fitted your hatch frame in whats to stop the cut joists in the 3m span direction wanting to drop down?

 

[dan_cup]

So when you have cut all the joists and fitted your hatch frame in whats to stop the cut joists in the 3m span direction wanting to drop down?

I kind of alluded to this, or am I jumping the gun thinking its ok to cut so many joists?

I would be attempting to follow usual practise of trimmers & sistering etc but is it allowed across several joists?