Spiral staircase construction

Sounds like you have most of the work figured out. For marking the risers, one good way is to take some butcher paper (fanfold printer paper is also good for this) and wrap it at the angle you want onto the pipe and measure the length. Mark the paper at 1/11 of that distance and you have the riser positions. Punch the pipe at those locations for a marker and start welding. For bending the ballister, just run your material through the bender and weld afterwords as necessary to get the full length. Don't worry too much about the rise as this will get fixed as you weld it in place although keeping the angle about right will help. Tension springs show that the material will go up right.

-- Why isn't there an Ozone Hole at the NORTH Pole?

The butcher paper idea is great! Thanks!

John

Don't forget about headroom--if you design too few treads per revolution you'll have to stoop as you go up. If I'm considering everything poroperly, you'll want at least 10 treads per rev.

I'll cut a 1

I've seen spiral handrails made up from a bundle of smaller rods. I don't know whether they were bent bundled together and then tacked to stiffen up the rail, or if laid in place one at a time and tacked as required.

I built a wooden spiral staircase for my house (actually it's three straight steps, seven winders, then 3 more straight) and it was a much bigger job than I planned. The handrail was by far the hardest part. Welded steel would have been much easier.

Ned Simmons

I think most spirals use the next step to support the front edge of the step above,and use the space under the step as toe space, mebbe the baluster goin through both steps.......I guess what I am saying is if the angle has its verticle part facing front, it will use up foot space, and if it is in the back it will leave the front edge flopping around

I think 3 inch pipe will look small when you are done......

I think 1 inch round thinwall tubing and a torch would work as a railing, bendit and heat as required, mig it to the balusters on the way by......

if you make a sprial big enough to be comfy, it takes up about the same space as a stairway....

Ned Simm> >

I have a back issue of Fine Homebuilding somewhere with an article on spiral stair much like you describe. This is more of a feature artile than do-it-yourself, but might have some ideas for you. Let me know if you want, I'll scan it and send it to you.

I do a lot of staircases. All steel, sometimes with wood treads.

Whenever somebody asks for a spiral I refer them to any of 3 shops in Seattle who do nothing but spirals. I don't mind installing it and adding detail stuff, but it is just more practical to have the stair fabbed by the guys with all the jigs and experience. I have built spirals from scratch, and it is just too much space and time.

I have built 3 open tread spiral stairs and have a few suggestions.

I would strongly recommend that you not weld the treads to the support column. If you misfigure anything you will be screwed. For maximum flexibility weld the tread supports to collars with an ID that fits closely over the support column and one riser in height and secure them in place with 3 or 4 set screws. You can then make minor adjustments to the run after it is in place and it takes a lot less effort and space to fabricate.

Riser height should be something between 7" and 8.5" that divides evenly into the distance between floors. Be very careful here as the error is cumulative. The tread width 2/3 of the way out from the column can be figured by subtracting twice the run from about 24" and add 1" for overlap. For the steepest safe angle use 21". For the lowest safe angle use 27". For example an 8" rise should have a run of (24+1)-(2*8) or 9". Err on the side of wider as you can increase the overlap on final adjustment but gaps should be avoided.

Drill and tap the collars in 3 places for the set screws and weld on the tread supports so that the top of the tread is even with the top of the collar. You can weld the top collar to the landing but it will be easier to erect if you weld a flange to it and bolt it to the platform after the column is in place.

The column should be 6" dia minimum heavy wall pipe and the length should be the floor to floor distance plus the rail height. Weld a flange on the bottom to fix it on the lower floor. Attach the wooden treads only to the bottom 3 or 4 tread supports. Set the column on saw horses and thread on the treads. Distribute the treads around the column and temporarily fix in place. Set up and plumb the column, fix the bottom thread in the desired position and then redistribute the threads evenly.

I make the banisters out of solid wood. Spindles are 1" OD pipe with a short piece of round bar drilled and tapped 1/4-20 welded inside the end. After the staircase is in place and adjusted I set the spindles and make a pattern for the banister that covers 3 or 4 spindles. Then I bandsaw the banister out of 5/4 wood. In the ends of each section I cut a horizontal slot 1/2" wide and about 2" deep for a joining insert. I cut the inserts over size and sand smooth once the banister is in place. Joints should not be located over a spindle. When fitting the banister I stick short lengths of 1/4" threaded rod sharpened on one end into the spindles and press the banister down to mark the drill holes. Drill and countersink the screw holes and then fasten with flat head screws and plug the holes.

Thank you, Glenn and everyone, for the useful info. I'll synthesize the info and go to it. BTW, Glenn, your boat project is amazing.

John