# staircase support



## StevieB (10 Sep 2009)

Quick query - if you were putting up a steel 'I' beam to support the top end of a staircase, what is the minimum size of a support post for one end of that 'I' beam (the other end will be on a padstone and embedded into the house wall by 4-6"). would you be happy with a 4" x 4" treated timber post (not a cheap fence post from B&Q but a decent timber one) or would you want a steel support post as well? Do not really want a timber beam as the depth to get suitable support is eating into headroom below the staircase, so would prefer a steel 'I' beam.

The I beam will be a max of a metre long and all that will be hanging on it will be a wooden staircase. Most staircase support beams are 4x4" timber posts or less are they not, with the top end in hangers from a timber floor joist? Reason I do not want to have to go to a metal post is that I do not have welding gear and will have to get someone to weld a plate on for bolting the 'I' beam and support post together. With a timber post it is alot easier to attach to the 'I' beam.

Steve.


----------



## trousers (10 Sep 2009)

Steve

Not sure I've got your drift.
If you are hanging the top of the flight on your proposed I beam, and its only 1m long (ie width of stairs plus support each end), then I think that is complete overkill.
Presumably at the top of the flight there is a landing constructed of joists and floorboards?
If so, the "trimmer" (that the top of the flight hangs on) would be the same depth as those landing joists, and possibly doubled up.
Since all the weight of the flight is carried at each side (the strings), the only weight the middle part of the trimmer carries is you when you step on it.
Therefore I would think that even if your landing is made up of only 4 x 2 joists, this size doubled up would be sufficient.
Bury one end in the wall and support the other end on a 4 x 4 post.

Have I missed a vital element somewhere, or are you just a belt and braces man :?:


----------



## StevieB (10 Sep 2009)

Thanks Trousers - sorry I was probably not clear enough! Resting on the 'I' beam will be one end of those landing joists, three in total and each approx 3ft long. It is a cellar staircase and I am removing a brick Victorian staircase which is held together with Victorian horsehair, spit and thin air. I may be able to add an extra trimmer as you suggest off a joist hanger and then the staircase is not an issue but until the brick staircase is removed I am not sure - all I can definately say for the moment is that there is no trimmer now. 

If you therefore ignore the staircase and were to consider an I beam supporting a small landing of approx 3ft square below 3 3ft joists, would you be happy with a 4x4 post supporting one end of the steel I beam?

some pics would probably help but its an enclosed area and I am not sure they would come out particularly well!

Steve.


----------



## trousers (10 Sep 2009)

Steve

Is the steel I beam there already, or are you proposing to insert a new one?

If you are going to insert a newbie, then I would normally expect to see a vertical steel box section or channel section to support it. However.........

If I read you correctly, the landing joist are only 3 feet long, and aligned at right angles to your proposed I beam. But how deep are they? And do you intend to put the I beam under the ends of the joists?

The normal construction would be one (or usually 2 bolted together) timber joists (trimmer) where your proposed beam will be, but of the same depth as the joists, and in the same horizontal plane. The joists would sit in metal hangars nailed to the trimmer. One end of the trimmer is buried in the wall, and the other end (in your case) sits on top of, or is fixed to the side of a 4 x 4 timber post. The stairs then "hang" on the trimmer such that the top tread is flush with the landing floorboards.

As I said before, I think steelwork is overkill. The loads just don't warrant it. Unless of course you've been given a bit of I beam and want to use it and save on the cost of a couple of bits of wood :roll: 

ps edit. Sorry, its late. Just noticed you're taking out a _brick_ staircase. So ignore the bit about hanging the stairs over the trimmer.
The rest still applies though!


----------



## StevieB (11 Sep 2009)

Thanks Trousers, really appreciate your comments. Totally agree that a trimmer is the way to go if at all possible, but I cannot see the top of the staircase at the moment so am considering a worst case scenario before I take it out and have an 'oh bu**er' moment! I think I am sorted now but will post again if I get into trouble  

Steve.


----------



## BigShot (11 Sep 2009)

As far as a timber post under an RSJ.
No way.

If you were getting building regulations approval for it they'd want to see a steel stanchion of some sort supporting that end, that in turn would need to be on a suitable footing.

That stanchion would, in most sttings like you describe, be Square Hollow Section - size dependent on the loads imposed on it.


For a 1m "stair trimmer" (as that's what the beam we're discussing would be called) an RSJ is complete overkill.
Toursers' description of how the stair and trimmer would be put in and the floor hung from that is accurate. Multiple beams should be bolted at 600mm centres (for a 1 metre trimmer I'd suggest 3 bolts through the centreline of the beams, one at each end and one in the middle).
When nailing joist hangers to the beam, nail every hole.

If you are using an RSJ, you'll need to bolt timber into the web of the beam (that's the indented bit of the I shape) and hang the joists from there so either way you'll need timber.
That is, unless you intend to rest the ends of the joists on top of the steel, in which case you'll need to secure them so they don't fall over.

I'd be really surprised if - with 3 ft joists at the landing - an RSJ would be necessary. In fact it would take a pretty long run of unsupported floor joists to require a steel to trim a 1 meter gap unless you've got to keep to a strict depth requirement, and it doesn't sound like you do.

If in doubt and you really want to be certain you're putting something adequate in, get an engineer to do a calculation for you.

You'll need the length of the stairs (measured on plan) the length of the floor joists sitting on the stair trimmer and the length of the gap the stair trimmer has to cross.
If you want a calcualtion for the post the length of that will be enough info for him.
If you want the bearing (padstone or bearing plate) calculating too, you'll need to tell the engineer what kind of brick it's sitting on - I have no clue how to go about finding that out. Not my department. I tend to assume some seriously weak, crumbling brick and go with whatever that needs, worst case scenario it's just right, best case it is overkill. Unless the mortar below the bearing is crumbling too, in which case that'll probably need fixing too.

It shouldn't cost too much to have that done and you'll have the peace of mind that comes with an engineer's calculations.


I'm sure this following bit is completely unnecessary but something tells me I should include it...
The contents of this post are opinion and should not be considered "advice". You should consult a structural engineer before undertaking works and obtain building regulations approval for any modifications you make.
If you follow anything mentioned in this post and get hurt, killed, or somehow damage your house or any other property it's your own fault and nothing to do with me, guv.

I bloody hate disclaimers but (though I don't think for a minute you're in their number) there are a lot of idiots who'll take any excuse they can to get hurt and sue someone.

Best of luck with the works, I do hope you don't have any "oh pipper" moments.


----------



## StevieB (11 Sep 2009)

Thanks bigshot  copious photos will be provided soon (well before xmas anyway I hope) as half the cellar is my workshop and I am doing a complete refurb of it. The other half is to be a big boys playroom - I desperately want a pub size pool table in there hence the requirement for open plan stairs. Not sure it will fit even then but I can dream.....

No buildings regs involved 8-[ Heck if they are not worried by the extra downstairs loo, me re-roofing and me rewiring the entire house (I phoned and asked honest!) I am sure they will not notice the cellar staircase is wooden and not Victorian brick.

I promise not to sue you if I kill myself doing the job and drop a brick staircase on my head :wink: 

Steve.


----------

