predicting metal deflection - guestimate

[inphx]

In one of my hairbrained ideas i preordered a spriral staircase. The "as-built" home floor dimensions came out 1.5" too low and need to find a way to squat down the 105" an additional 1.5". (so the last step on top is symetrical in height)

Based on building codes if nothing can flex then I need to find 4 places to have it 3/8" lower (steps can not vary in height over 3/8" per code). There is the top and bottom step and 2 joins i can play with if i have to. Or just take a 4 step secion and adjust the fab.

Or i can try bolt it up and count on the weight of the assembly to distribute the 1.5" compaction hopefully evenly across the entire assembly.

There are glass steps that set into the stainless steel.

I am inclined to bolt it together and see how it works out. Any advice/predictions. I kind of expect it to bulge out to a larger diameter enough to meet my needs and to not have any super odd sloped steps (thats what i hope for)

 

[neonnblack]

Its very hard to see in the pic but maybe you can have a cnc shop cut out new feet for the bottom takes it closer to the floor. If im understanding the predicament correctly.

 

[inphx]

Predicament is by code - variance of any step height can be 3/8" max... so if its all rigid i would need to find 4 steps to do a 3/8" tuck.

 

[jeff g]

Hi
Looks like 20 steps top to bottom.

20 into 1.5" = 0.075" per step

Try building the spriral staircase to see the squat down.

Is there any play in the holes. How significant is the hole fit ??????

Can you drill out the holes by 1/32, build 5 steps to see the squat down,
if not down to spec then 3/64 then 1/16, to get the squat down ???????

ps
after drilling, when building the staircase level the step, flat & equal in height

 

[srmofo]

I think I would be having a talk with the builders of the home as to why the dimensions dont match the drawings.

Make them eat the cost of the stairs...

If Im understanding this correctly.

 

[dewalt378g]

It looks like you already have it in a temporary setting. Simulate the "squat" by shimming it up 1.5" and see how it reacts. If you're successful check level on the treads and check the fit of the hand rail. You just might get lucky.

 

[usdemt]

Hope it works cause those stairs are sweet.

 

[betweencenters]

Even with tight tolerances on the bolt holes there is no doubt enough "wiggle room" to sneak 1 1/2 " out of that height. Bolt it up. You`re welcome.

 

[inphx]

Thanks guys - day job takes precedence - will update all at weekend. Architecht and framer are in different planets and lumber supplier is happy to keep altering. As the "General contractor" i own the disconnects.

 

[inphx]

It's in correctly - I ran out of swear words but in the end its suhweeet...

 

[PugetDude]

It's in correctly - I ran out of swear words but in the end its suhweeet...

So how did you get the 1.5" out of it?

Brute force & ignorance (my usual approach) or finesse?

Nice looking staircase, BTW...

 

[inphx]

Didnt need to - built to spec. Embarrassed to say either framer is houdini or the tape measure to top of beam was wrong in my spot check/panic.

 

[EdT]

I have heard of a lot of cheapo tapes being off a lot. Don't know if that's the case here, but it's a possibility. 1.5" in 10 feet is only a little over 1% "off".

 

[dutchgray]

Or the tape was hooked on it end piece rather than the end, that happens a lot.