joist strength

[Martin Carroll]

I am putting a megaflo HW cylinder in the renovation and need to construct the floor of the airing cupboard (which is above the staircase).

The weight when full of the particular model will be 228Kg and I was wondering how I ensure that the floor it is standing on is strong enough for that weight.

Is their an easy way to calculate the joist size I need to use?

Cheers

[RW]

Perhaps mount it on a suitable wall mounted bracket as well ?

[jim]

joist sizes used to be specified in tables to the Building Regs, unfortunately my copy is old & probably out of date: if you are lucky someone will be along soon with chapter & verse. If not, I will look out the info for you tomorrow.

Apart from the load (228Kg), you need to know the span of the joist & the distance between joist centres to lookup (or calculate) joist sizes.

The other point you should watch is that you mention a staircase. Simple Bldg Reg joist sizes are mainly for joists fully supported at both ends, eg by walls. If the floor is otherwise supported - suspended, held up by a Newel, on a cantilever, part of a truss, etc - the whole structure should be reassessed for strength. If in doubt please repost with more info.

228Kg is not that much of a weight - only 3 average adults & a floor to BReg stads should support that. However if left as a point load for a prolonged time it could be enough to cause a floor to sag.

HTH

[dwtowner]

Try the Superbeam software:

You can get a demo version which will give you enough features to do your calculation.

dan.

[Michael Chare]

The weight, which is about twice that of my ordinary HW tank, will be less of an issue if the tank is next to an outside wall which supports one end of the joists.

It must be a common problem for tanks the size of yours so you might be able to get some advice from Megaflow.

[jim]

You will find tables of acceptable joist sizes in Appendix A of Building Regs Approved Document A 1992 edition at

the tables are for good quality - ie graded - timber.

Also note that the sizings given are for an assumed "live" load on the supported as given in the text of the regs (effectively so many Kg/ Newtons per square meters) - thiat is the assumed max load of the room contents + passing traffic. The tables allow in addition for the self weight of the joists.

HTH

[Martin Carroll]

In article , jim writes

Cheers

I will check these out.