How to strengthen tip of loft joist?

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Hi guys,

Installing new joists in the loft so it can be boarded for storage. Ive had to cut the joists to the angle of the rafters so they can sit on the wall plate, the problem however is that the thickness of the tip of the joist of the joist at the rafter end where it sits on the wall plate is only around 4cm (see attached pic).

Im wondering if there is anything I can do to strengthen the tip of the joist where it sits on the wall plate?

I considered using a splice plate and cutting it to the angle of the joist however I have had to cut notches out of the joist to fit over the ceiling joists (dont ask, it had to be done this way) and the ceiling joist is very close to the wall, so no real space for the splice plate to fit.
I also considered using those plates that you nail to the side of the joist, however im worried that sinking a load of nails into such a small area of the will make it even weaker and possiblly destroy the tip of the joist.

These joists only cover a 2m wide section of the loft, due to the layout this is just an awkuard part, all of the joists will be joined together with noggins joined via pocket holes so each joist will also share the load with the joist either side, and the rafter, and they are C24 graded.

So as mentioned if there a way I can strengthen the tip of the joist where it is only 4cm thick, if I need to strengthen it at all.
 

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Are the existing joists underneath not sufficient to spread the load?

Blup
 
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Im wondering if there is anything I can do to strengthen the tip of the joist where it sits on the wall plate?
40mm thickness at the end isn't a lot, but f you are concerned about load carrying rather than trying to strengthen the joists I think it would be more effective to either double them up (sister them) or halve the spacing between them (e.g from 400mm to 200mm centres) by inserting extra joists

I also considered using those plates that you nail to the side of the joist, however im worried that sinking a load of nails into such a small area of the will make it even weaker and possiblly destroy the tip of the joist.
They are called nailing plates and I think you fundamentally misunderstand their purpose - they are relatively thin and ìn themselves won't add much strength to a single piece of timber, rather they are designed to stop timbers in butt joints from moving, e.g as in truss roof frames or timber frame structured

These joists only cover a 2m wide section of the loft, due to the layout this is just an awkuard part, all of the joists will be joined together with noggins joined via pocket holes so each joist will also share the load with the joist either side, and the rafter, and they are C24 graded.
Firstly, pocket holes are complete overkill and lets face it you'd never find a joiner using them for this purpose. Complete overkill IMHO, when you can simply drive screws through the joists into the ends of the blocking, either straight or at a slight angle to avoid an existing block. Use decent size screws, something like 5.0 x 100mm ones, or 6.0mm screws if dealing with larger section timbers (such as 7 x 3s)

Secondly, blocking or solid strutting does not really share the load between joists. What it does do is to stiffen a floor or ceiling structure by reducing the tendency of any single joist to twist when under load. In other words it makes the floor or ceiling less bouncy. On a 2 metre span I doubt that solid strutting would be necessary. If your joists need to carry more load then you can upgrade the strength (e.g move from C16 grade to C24), stiffen the joists by sistering them or reduce the joist centres by adding extra joists between the existing ones - or any combination of those three techniques. You can also add a stressed skin to the top of the floor (see below)

Were I doing this job I'd double up the joists, sistering them together using coach bolts (2 no. M8 or M10 per sistered joist). These sistered joists are normally pretty good at resisting twisting under load because of the increased thickness. I'd then ensure that any flooring was well fixed down to the tops of these joists - possibly by glueing it down then screwing down onto the joists at 150mm screw centres on the joists. By all means put in some solid strutting, but it would probably be superfluous
 
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