Piers for RSJ on Block & Beam Floor

[brennan2470]

If you're using the ceiling for light storage, I can't see why you can't sit the UB on the existing single-skin walls. If the loads are not too heavy, you can dispense with padstones and set the beam on steel plates as spreaders - this could avoid messy cutting out of brickwork.

If you tell your SE what sort of load you consider putting up there, s/he should be able to check fairly quickly whether its feasible to use the single-skin as support, without jumping into some elaborate Heath-Robinson scheme. The load-carying capacity will depend on the height of the wall above the foundation, the type of brick, and the spacing of the piers.

The piers are intended to reduce the 'slenderness' of the wall and hence to allow it to carry a little more vertical gravity load, and also provide a bit of extra stiffness against wind load.

Thanks. I’ll relay this to the s/e when I find one. The load is going to be circa 2 tonne however the RSJ will only act as a mid span for the joists, so the existing wallplates will be doing a lot of the work too.

I have spoken to a builder who has advised against placing the beam within the two single skinned walls for the following reasons:

1. One wall is adjacent to my garden and the RSJ will be visible from the other side of the wall and will require treatment to prevent it from rusting due to these reasons.
2. The other wall is a party wall (my garage, whilst detached from my property is oddly attached to my neighbours property!)

He notes that none of these are barriers, but add additional complexities and considerations.

His advice was to use steel goalposts at either end of the RSJ span, with welded plates top and bottom. The bottom would bolt to the floor, and the top would bolt to the RSJ (I have family/friends in the steel supply industry so the cost isn't AS much of a factor, before anybody jumps in!).

I have spoken to Bellway homes and they have advised me that the block and beam floor in my garage has been done to garage specifications (as expected). It has 450mm wide footings despite only being single skinned, and therefore one would assume that any steel goalpost would most likely sit atop these footings rather than the floor, but in any case the floor can take point loads of up to 900kg. There is 100mm of screen on top of the b&b.

Using ChatGPT and accurately describing the spans, loads, beam types, steel properties, as well as telling it to calculate based on British Standards, it gives me these results:

• Use 152x89x16KG/m UB if the primary goal is to minimize material use while meeting current loading conditions.
• Use 203x102x23KG/m UB for additional safety and reduced deflection, particularly if there is potential for future increases in loading.

I intend to use the latter of the two for future proofing (and over engineering). I appreciate that there'll be a few eye-rolls at me using AI to calculate an RSJ, but ultimately RSJ calculations are just that - calculations. Provided you put the right information in, you get the right answer out (at least I hope).

So with that, would you agree that a 203x102x23KG/m universal beam sounds about right to support a 7m x 6m timber floor structure whereby the RSJ is acting only as a centre span to halve the 7m to 3.5m, and the joists will be supported on 100mm wall plates at either end?

 

[tony1851]

The 203 beam you're considering would fine as long as you don't load the floor up with cylinder blocks and gearboxes.
What would you use as posts? 100 x 100 box section maybe?

 

[brennan2470]

The 203 beam you're considering would fine as long as you don't load the floor up with cylinder blocks and gearboxes.
What would you use as posts? 100 x 100 box section maybe?

The 7m x 6m floor space will consist of 3x6 joists weighing approx 250kg and 22mm T&G chipboard flooring weighing approx 600kg, plus my boxes of general household stuff, camping and leisure gear, etc, and me walking around. The load is shared between the two wall plates at each end as well as the beam. On the basis that the beam is bearing 1/3 of the load, I estimate it will be taking 750kg in a worse case scenario.

My friend had suggested using some material he already has, either 80x80mmx12mm box section or 100x100x4mm box section (of course I can get other profiles as well but these wouldn't cost me anything!). The sections would have plates welded top and bottom and be bolted into the floor with resin anchored thread, and bolted to the RSJ. I was also intending on bolting the columns to the wall to wall (every 500mm?) using resin anchors, just to keep them straight and upright.

Let me know your thoughts - thanks.