Steel Stairs Concrete Block Base

[unionworkeruk]

I am getting some steel stair frames installed at ground level- two stringers. I will provide the treads. The company tells me I have to proved a concrete base 400 x 400 X 200 on the ground under the floorboards at the base of each stringer . This would be about 1 metre below floor level.

Apart from me having to rip up the floorboards I am not qualified, trained or have any experience of shuttering or any other way of building concrete bases. I assume they will secure the stringers by attaching it to the block bjut how does that support the weight At the top it is drilled into the wall

I thought of hollow concrete blocks you can get from Travis Perkins and just placing them on the ground and filling them with ready mix.

I am just not sure of the method of securing the base for the steel stringers or who is responsible for providing them. Bit of advice is needed

 

[Deleted member 174758]

I thought of hollow concrete blocks you can get from Travis Perkins and just placing them on the ground and filling them with ready mix.

Probably far too soft and weak - what is required is a cast concrete footing, of similar density to the base of your house walls (assuming that you live in a relatively modern house), which will take the weight and loadings on the stairs without cracking.

For this application I'd consider concrete with either rebar strengthening or the use of a fibre admixture in the concrete for added strength. The concrete can be bought from a barrow service where they turn up with a truck and mix the exact amount required on the truck outside your house. All you do is to barrow it in, fill the form, vibro it (ideally) and tamp down. The main thing is that the top surface of the cast concrete must be level in both planes and relatively smooth and flat. Casting a concrete base like this in situ isn't too complex, nor does it require masses of kit

I am just not sure of the method of securing the base for the steel stringers or who is responsible for providing them. Bit of advice is needed

Generally you cast-in steel studs which are specifically designed for the purpose. That requires the use of casting cones to avoid concrete getting in the treads. Alternatively I'd ask if your supplier can fix using rag bolts (Rawlbolts) and whether or not he is prepared to drill the concrete and fix the stringers into place for you using Rawlbolts. The need to use Rawlbolts, and the requirement for them to be drilled and fixed into fairly strong solid concrete is why you can't use hollow blocks (which in any case wouldn't make-up a one-piece foundation) and fill them with concrete

 

[unionworkeruk]

Thanks for the info but surely it is the main contractor's responsibility to build the foundations the stringers are resting on or arrange for them to be done in the way he approves. That way I am covered if anything goes wrong. I have no experience of shuttering or concreting so have no real idea of what is safe or unsafe, structurally reliable or not etc.

The house is over 100 years old and under the floor boards is just a few brick piles for the joists and earth after 1m. Apart from what you have told me I have no idea what needs to be done and would not know if it was done properly or not. I think I need to see the main contractor again. Thanks

 

[cdbe]

Surely you give the specification for the pad provided by the stringer supplier to the contractor (including any supplied detail for fixing the stringer to the pad) and he builds it.
If there are no details it would be reasonable to assume that it will be rawl bolted to the concrete by the stringer installer.
What I would be concerned about is the depth under the floor - the 400x400x200 pad may be based on it being set in a solid concrete floor - a 400x400x1000mm+ high pier under a suspended floor may not be suitable - I would discuss this with the supplier, also you need to know whether the pad should finish flush with the finished floor level or below it, and check, double check, and recheck your measurements, particular floor to floor (or better still get the supplier to do this).

 

[unionworkeruk]

Yes, you are right cdbe. I have now told the contractor for installing the stringers that it is his responsibility to install the concrete bases even if he subs for the work, as long as it to a bonafide company that is covered for insurance. If I install them I am not covered and if anything goes wrong he could blame me for not building the bases properly.

He partly suggested it to save me money but something as crucial as the ground base for the whole structure should not be left to someone like me with no experience or knowledge of laying foundations for steel.

I am now getting it written into the contract with details of the bases included in all the drawings. I can then get them checked before signing any contract.

Thanks a lot for all the information and advice to everyone

 

[Leofric]

Just asking but why are you going for a steel staircase requiring these concrete bases etc when the floor is timber

 

[unionworkeruk]

Leofric. A minimal steel frame will show off the wood on the stairs far better then the usual wood frame which encloses the treadsin a box you will hardly see them and lames the hallway "small". . I have a small narrow hallway so I want the minimum of support and the maximum of wood . This ( https://www.pinterest.co.uk/pin/466615211391429398/ )is far larger than my terraced place but you get the idea.

So far I have collected planks of Ash, Oak, Walnut, Yew. Some still with the bark on the edge and will "display" the best of them on the stairs. I have also used reclaimed old wood on the floor as well but none on the walls in the hallway at least !

I am now 74 and this is my last big project so I am probably going over the top a bit, I admit, but scavanging wood in skips and on the street does help

 

[Leofric]

You can't have open risers like those in the picture can you Good luck with it anyway

 

[Deleted member 174758]

So far I have collected planks of Ash, Oak, Walnut, Yew. Some still with the bark on the edge and will "display" the best of them on the stairs.

Just remember that the going (slope) of the stairs will need to be consistent, making "natural" edges at the front almost impossible to incorporate. Also note that bark doesn't always stay attached to the host log and can come away unexpectedly. Being softer than timber is also wears faster. All in all I think the BCO might have issues with it.

As far as the risers go, the gap between the top of one tread and the underside of the next may not exceed 99mm (again, UK regs), although the way that I've seen of getting round this include the use of toughened glass "risers" and also the incorporation of stainless steel tensioned rods or ropes side to side in the riser space.

 

[Leofric]

The stairs need to comply with all the relevant requirements of Bldg Regs Approved Document K (view on internet) for dwellings . Can't go into all the details here.