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benjamincall 07-15-2010 01:34 PM

New rough opening to basement - spiral staircase
 
I'm cutting a new rough opening in my floor for a spiral staircase. Please corroborate my findings if you can:
  • A 61" staircase is about the minimum width necessary to achieve the 26" code minimum distance between the railing and the center pole
  • The opening for this staircase should be about 4" larger than the staircase size, i.e., about 65" inches
  • I will need to remove 4 joists at 16" on center to make a 65" opening (if I remove only three, I believe I would have only 1/8" clearance in some places after I drywall the rough opening)
  • The rough opening requires double headers and double trimmers since the header span is greater than 4 feet
  • I'll need to use joist hangers, since I'll be spanning 78.5" when I chop four floor joists
R502.10 Framing of openings. Openings in floor framing
shall be framed with a header and trimmer joists. When the header joist span does not exceed 4 feet, the header joist may be a single member the same size as the floor joist. Single trimmer joists may be used to carry a single header joist that is located within 3 feet of the trimmer joist bearing.
When the header joist span exceeds 4 feet, the trimmer joists and the header joist shall be doubled and of sufficient cross section to support the floor joists framing into the header. Approved hangers shall be used for the header joist to trimmer joist connections when the header joist span exceeds 6 feet. Tail joists over 12 feet long shall be supported at the header by framing anchors or on ledger strips not less than 2 inches by 2 inches.


I don't understand the portion highlighted in red. Wouldn't the cross section of the header be simply 1.5" x joist depth? I'll be using 2x8s to match the joist depth.

I'm going to build two temporary walls while I frame this box. I imagine leaving those walls in places would enhance the rigidity of the floor joists supported by the new header. I wouldn't have to worry about reinforcing the slab because the header is transferring the load to other joists, correct?

benjamincall 07-16-2010 01:40 PM

The inspector confirmed my plan. I'll match the depth of the floor joist for the header, double the header, double the trimmer, and use a joist hanger for the header.

BigJim 07-16-2010 02:27 PM

Sorry I didn't see your thread until just now. By the way, if you will only have 1/8 clearance using 1/2 sheet rock, you may consider using 1/4 inch instead.

Jim

benjamincall 07-16-2010 04:04 PM

Quote:

Originally Posted by jiju1943 (Post 470423)
Sorry I didn't see your thread until just now. By the way, if you will only have 1/8 clearance using 1/2 sheet rock, you may consider using 1/4 inch instead.

Jim

Good idea! The staircase manufacturers want you to add four inches to the size of the staircase to calculate the rough opening. Can you think of any reason, other than making allowance for error, not to go a little tighter?

Gary in WA 07-16-2010 04:28 PM

Is the trim thickness included? Do you have a stair web site picked out that we could look at?

Be safe, Gary

BigJim 07-16-2010 04:30 PM

Ben, the only reason I can think of not closing the opening in more would be for your hand or fingers to clear the wall on the handrail. Is this your first circle stairs to install? It is some fun for sure but I did enjoy installing the few that I did.

kwikfishron 07-16-2010 04:55 PM

Quote:

Originally Posted by jiju1943 (Post 470481)
Ben, the only reason I can think of not closing the opening in more would be for your hand or fingers to clear the wall on the handrail. Is this your first circle stairs to install? It is some fun for sure but I did enjoy installing the few that I did.

If your holding that rail down the stairs you would want at least a few inches, four sounds like a good number to me.

Joe Carola 07-16-2010 05:01 PM

Quote:

Originally Posted by benjamincall (Post 470469)
Good idea! The staircase manufacturers want you to add four inches to the size of the staircase to calculate the rough opening. Can you think of any reason, other than making allowance for error, not to go a little tighter?

Ask the stair manufacture that question. They are the ones who are giving you the rough opening. You should follow what they say. Going smaller than the manufactures RO's is never a good thing whether it's for stair, windows or doors.

benjamincall 07-16-2010 05:53 PM

Quote:

Originally Posted by GBR in WA (Post 470480)
Is the trim thickness included? Do you have a stair web site picked out that we could look at?

Be safe, Gary

I believe that clearance is from the finished surface. Here's a link to the calculator from the company I'm considering:
http://www.spiralstairsofamerica.com...Calculator.php

Quote:

Originally Posted by jiju1943 (Post 470481)
Ben, the only reason I can think of not closing the opening in more would be for your hand or fingers to clear the wall on the handrail. Is this your first circle stairs to install? It is some fun for sure but I did enjoy installing the few that I did.

Good point about the fingers. I thought handrails exist to meet code; who actually uses them? :) I haven't put one of these guys in before. By fun do you mean "having people drop bar clamps on your head" kind of fun?

Quote:

Originally Posted by kwikfishron (Post 470497)
If your holding that rail down the stairs you would want at least a few inches, four sounds like a good number to me.

Two smart guys came up with that answer, so that's likely the idea behind the clearance.

Quote:

Originally Posted by Joe Carola (Post 470508)
Ask the stair manufacture that question. They are the ones who are giving you the rough opening. You should follow what they say. Going smaller than the manufactures RO's is never a good thing whether it's for stair, windows or doors.

I'll try calling them next week when they're back in the office. I don't this the recommendation has to do with sructural concerns, so if it's only a matter of giving up a few inches of usable railing, I might make the compromise to avoid cutting a joist. I'll provide an update when I found out what the story is.


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