Airing cupboard above a stairwell

[Donkmeister]

I need to move my hot water cylinder as it is in the way of a new bathroom.

Space-wise, the best location would be above the stairwell, with the joists supported at one end by an external wall, and at the other by a structure yet to be defined.

At the external wall end, I would use joist hangers fixed into the mortar of the inner skin (1920s cavity wall).

At the other end I have lifted the floorboards to see what structure I am dealing with. The landing has 3 joists running in parallel, approx 3 metres long, approx 175mmx56mm (7" by 2 1/4 ", as it's 1920s!).

I have chipped off some plaster and the joist highlighted in red below, appears to be supported by a wall of red bricks along its entire width and length. The wall is approx 15cm thick, so may be double-width. However, the edge of the joist is right up to the facing edge of the brick.

I was planning to use 3 joists, 47x147mm, 1 at either end and one in the centre (i.e. 450mm centres). Floor would be marine ply, 18mm. Does that all seem right for a loading of approx 200kg (150kg for tank, 10-20kg of linen, plus studs and plasterboard to form the wall of the cupboard)?

Untitled

• Donkmeister
• 16 Jan 2011
• 1

The next question is how to support the landing end of those joists approx 40cm above the red-highlighted joist without risk of the structure "skewing" into a parallelogram... If I build a frame from 4x2s with diagonal bracing, and coach bolt that to the top of the red-highlighted joist, will that do?

Also, as I'm planning on installing a shower pump in this cupboard, do I need to take into account vibration? Possibly a silly question!

Thanks for any help you can give me!

 

[Donkmeister]

I realise I went off on a bit of a ramble there!

In short, my questions are:

1) If a joist is support along its length by a load-bearing wall (red brick), to what degree is the load capacity of the joist increased?

2) Is the following sufficient: 147x47mm joists with a design length of approx 1m, 45cm centres, total loading approx 70kg per joist, 3 joists in total, joist hangers at one end, bolted onto a wooden structure at the other.

3) Do I need to take into account the vibration of a shower pump?

Cheers