Strengthening loft joists

4 Sep 2013
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United Kingdom
I am looking to strengthen the joists in my 1890 Victorian property. Currently the ceilings are down do the joists are fully exposed. A chimney stack runs right up through the middle and there are two trusses. One each side of the chimney stack. The existing joists run from the exterior wall on a wooden wall plate, then underneath the truss where they are nailed to the bottom of the truss. At the point where the joist goes under the truss the joist has also been chopped to half the depth and then nailed to the underside of the truss. The joist then goes along to the other wall plate around the chimney. The situation i have just described is the exact same of the other side of the chimney.

I'm proposing to fit stronger, deeper joists in between the existing joists and leaving the existing ones where they are. I will sit the new joists on the wall plate at the exterior wall end and then using joist hangers on the truss fix them here.

Can anyone see any issues with this?
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I'm assuming a fully hipped roof and when you describe the new joists as "deeper" I envisage a lowered ceiling lowered on the joist hangers, is that what you're proposing? If so nothing wrong so far, however as an alternative I offer the following - new same size joists cut and fitted parallel to existing and fully nailed to them to provide an almost doubling of strength and right angle brackets fitted where they cross the trusses. The benefit, as I see it, is no extra load applied to existing trusses, but roof/joists tied together...pinenot :)
Hi Pinenot. Thank you for reply

My house has a gable roof. I am trying to firstly strengthen the joists, but to also increase the height of them so I can raise the loft floor space and increase the amount of insulation between the joists. I'm also trying to raise the joists height so I can tack the electric cabling on top of the new joists so its clear of the insulation. The ceiling height I want to remain the same

There is a truss that runs across at right angles to the ceiling joists. The ceiling joists run under this truss but have been cut and nail up on the underside of this truss. The joist then continues where it sits on a support by the chimney.

I'm not sure whether its best to you joist hangers and this truss, by the gable end wall plate and the chimney stack which I hope would strengthen the existing joists. I could then run batons along these joists which will increase the height so I can sit floorboard on etc.

Or run new joists all together from one end to another invetween current joists.

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