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-   -   Will these stairs pass IBC code? (http://www.diychatroom.com/f19/will-these-stairs-pass-ibc-code-161715/)

jonrya91 10-31-2012 09:05 AM

Will these stairs pass IBC code?
 
These are stairs that i recently installed onto the front of my house. They lead up to a large porch which is shown on the right.

I think i know the answer, but i just want to double check with someone else. I've run this by my inspector over the phone numerous times, but i don't think he understands. I'm concerned that because of the 1.5" overhang on the porch, the tread length differences are more than the permissible amount.

Thanks.

https://lh3.googleusercontent.com/-4...960/STAIRS.jpg

jcarlilesiu 10-31-2012 09:09 AM

I believe 1" nosing max..

Also, although I believe treads have to be 10" min. in depth, and your design conforms, there is a better solution. Adding a 1" nosing to the rest of the steps will increase the tread depth to 11.5 and eliminate a tripping hazard caused by the shallow tread.

rjniles 10-31-2012 09:11 AM

I cannot answer your question about code but it seems that 1.5" overhang will be a toe catching tripper. Can't you build that riser out to decrease the overhang?

jonrya91 10-31-2012 09:22 AM

Do you mean the tread?

joecaption 10-31-2012 09:46 AM

http://www.precisionstairsystems.com...copy_1__1_.pdf

jonrya91 10-31-2012 11:11 AM

Thanks Joe - i think my stairs fail according to R311.7.4.2. My max tread depth is more than 3/8" larger than my min tread depth.

They should also fail per R311.7.4.3. Max projection exceeds 1.25".

Sound right?

jcarlilesiu 10-31-2012 11:20 AM

Quote:

Originally Posted by jonrya91 (Post 1041704)
Thanks Joe - i think my stairs fail according to R311.7.4.2. My max tread depth is more than 3/8" larger than my min tread depth.

Your drawing in the first post shows a typical tread depth of 10.5"

I am confused.

jonrya91 10-31-2012 11:30 AM

jcarlilesiu - I am too.

Am i wrong to think that tread depth is measured nose to nose?

GBrackins 10-31-2012 11:43 AM

the IBC and IRC have different stair requirements ..... I've listed both requirements as shown in the 2009 I-Codes. Your state or local jurisdiction may have modified these requirements. For example Massachusetts allows a maximum riser height of 8-1/4" and a minimum tread depth of 9" for residential construction.

Hope this helps!

IBC requires:

1009.4.2 Riser height and tread depth. Stair riser heights shall be 7 inches (178 mm) maximum and 4 inches (102 mm) minimum. The riser height shall be measured vertically between the leading edges of adjacent treads. Rectangular tread depths shall be 11 inches (279 mm) minimum measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread's leading edge. Winder treads shall have a minimum tread depth of 11 inches (279 mm) measured between the vertical planes of the foremost projection of adjacent treads at the intersections with the walkline and a minimum tread depth of 10 inches (254 mm) within the clear width of the stair.

1009.4.5 Profile.
The radius of curvature at the leading edge of the tread shall be not greater than 9/16 inch (14.3 mm). Beveling of nosings shall not exceed 9/16 inch (14.3 mm). Risers shall be solid and vertical or sloped under the tread above from the underside of the nosing above at an angle not more than 30 degrees (0.52 rad) from the vertical. The leading edge (nosings) of treads shall project not more than 11/4 inches (32 mm) beyond the tread below and all projections of the leading edges shall be of uniform size, including the leading edge of the floor at the top of a flight.

Exceptions:
1. Solid risers are not required for stairways that are not required to comply with Section 1007.3, provided that the opening between treads does notpermitthe passage of a sphere with a diameter of 4 inches (102 mm). 2. Solid risers are not required for occupancies in Group I-3 or in Group F, H and S occupancies other than areas accessible to the public. There are no restrictions on the size of the opening in the riser. 3. Solid risers are not required for spiral stairways constructed in accordance with Section 1009.9. 4. Solid risers are not required for alternating tread devices constructed in accordance with Section 1009.10.

IRC requires

R311.7.1 Width.
Stairways shall not be less than 36 inches (914 mm) in clear width at all points above the permitted handrail height and below the required headroom height. Handrails shall not project more than 4.5 inches (114 mm) on either side of the stairway and the minimum clear width of the stairway at and below the handrail height, including treads and landings, shall not be less than 311/2 inches (787 mm) where a handrail is installed on one side and 27 inches (698 mm) where handrails are provided on both sides.

Exception:
The width of spiral stairways shall be in accordance with Section R311.7.9.1.

R311.7.4.1 Riser height. The maximum riser height shall be 73/4 inches (196 mm). The riser shall be measured vertically between leading edges of the adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm)

R311.7.4.2 Tread depth. The minimum tread depth shall be 10 inches (254 mm). The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread's leading edge. The greatest tread depth within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm). Consistently shaped winders at the walkline shall be allowed within the same flight of stairs as rectangular treads and do not have to be within 3/8 inch (9.5 mm) of the rectangular tread depth.

Winder treads shall have a minimum tread depth of 10 inches (254 mm) measured between the vertical planes of the foremost projection of adjacent treads at the intersections with the walkline. Winder treads shall have a minimum tread depth of 6 inches (152mm) at any point within the clear width of the stair. Within any flight of stairs, the largest winder tread depth at the walkline shall not exceed the smallest winder tread by more than 3/8 inch (9.5 mm).


R311.7.4.3 Profile. The radius of curvature at the nosing shall be no greater than 9/16 inch (14 mm). A nosing not less than 3/4 inch (19 mm) but not more than 11/4 inches (32 mm) shall be provided on stairways with solid risers. The greatest nosing projection shall not exceed the smallest nosing projection by more than 3/8 inch (9.5 mm) between two stories, including the nosing at the level of floors and landings. Beveling of nosings shall not exceed 1/2 inch (12.7 mm). Risers shall be vertical or sloped under the tread above from the underside of the nosing above at an angle not more than 30 degrees (0.51 rad) from the vertical. Open risers are permitted, provided that the opening between treads does not permit the passage of a 4-inch diameter (102 mm) sphere.

Exceptions:
1. A nosing is not required where the tread depth is a minimum of 11 inches (279 mm). 2. The opening between adjacent treads is not limited on stairs with a total rise of 30 inches (762 mm) or less.

jcarlilesiu 10-31-2012 12:02 PM

Quote:

Originally Posted by jonrya91 (Post 1041713)
jcarlilesiu - I am too.

Am i wrong to think that tread depth is measured nose to nose?

Yes.

Its measured tip of nosing to riser.

That way, you can extend your treads another inch or so by putting a nosing on the rest of the steps.

jcarlilesiu 10-31-2012 12:06 PM

GB,

There is some exclusion in IBC somewhere that allows exceeding the 7/11 requirement so long as a ratio is maintained. At least there used to be, could have changed and was from BOCA or other.

I do almost exclusively commercial architecture, so those are the codes I am most used to.

Easiest way to design stairs is to take you landing to landing height in inches. Divide by 8 (residential) which will tell you how many risers. Take that number of risers times 10" and that will be the horizontal run. Add a 1" nosing at all treads to make the stairs safer and your done.

GBrackins 10-31-2012 12:38 PM

I'm on the other end of the scale from you, 99% of my work is residential .....

the easiest thing to do is call the building official and verify the requirements of this jurisdiction.

like I said a lot of states have modified the IRC to allow the older 8-1/4" R x 9" T. I'm not aware of an exclusion on the 7/11

jonrya91 10-31-2012 12:44 PM

Gbrackins - Building inspector told me 9" min tread depth, 8-1/4" max riser height. I tried to expain that the porch has an 1.5" overhang....he told me as long as i have 9" from nose to nose i'm good.

The problem is that the lower stair is 10.5 inches. It's 1.5" larger & more than the 3/8 allowable.

I might just let him inspect it and see what happens.

GBrackins 10-31-2012 12:49 PM

that's what I'd do ...... let him find the issue (doubt he will)

GBrackins 10-31-2012 12:50 PM

good luck!


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