Roof access seems to have become more important to me as I got older (wiser?). Two realizations dawned on me. 1. Climbing a ladder to visit a roof is pretty ’thrilling’ for the unaccustomed. 2. How is anyone motivated to maintain the roof and the stuff up there if they can't easily get to ’up there’. Reason 2 is the main reason to build easy access to the roof into every project - even a remodeling.
So what are the options?
A. Do nothing - we’ve already covered that. However, this isn't an option for 3-story (or more) buildings because of code.
B. Permanent ladder and roof hatch - this is better than nothing, but it is hard to climb a ladder with a tool box, roofing repair materials or even a clipboard. It is even more difficult if the trip is over 20’ and you are caged in. OSHA! This is about a $3000 solution costing you just 10 SF, but it’s only rudimentary. If lack of maintenance creates problems because of roof access difficulties, you will regret not spending more.
C. Ship’s ladder and hatch - now we’re getting somewhere! This roof access solution is pretty good. Just about anyone with business on the roof can easily get there with most of their tools and materials. The cost is about $8000 and you give up about 50 SF, but I think it is worth it.
D. Stair extension to the roof - Heaven! You already have a stair, take it all the way to the roof. So this is easy - and kinda expensive, and not always attractive, and surprisingly quirky to detail. The cost is north of $30,000, which, although high, might be a bargain in the right circumstances. Circumstances like expensive equipment on the roof to maintain, or extensive flashings to maintain. (See my quick Scalar. calculation.)
Once you have settled on a type of roof access, the next steps look like this:
STEP 2 - 10 Ft. Distance - bear in mind that codes require a safety margin of 10’ from the point at which you emerge onto the roof to the nearest edge of the roof. Less than 10’ requires a permanent guard rail.
STEP 3 - Draw a section - by drawing a section you will have an idea of how much room your ship’s ladder will require. Research this link to see how to design a ship’s ladder.*
STEP 4 - Work out head room - another cross section issue. Draw a line parallel to the nosings of the stair with a 7’ vertical clearance. This determines the minimum length of the roof hatch.
STEP 5 - Size opening - you worked out the length, now the width. This depends on your stair width, but should be at least 12 inches wider. The structural drawings need to show how this opening is framed.
STEP 6 - Detail roof opening - the components of this detail include the structural framing of opening, the roof hatch, flashing to the roofing, and anchorage of the stair. I like to include a ladder extension device made by Bilco, the Ladder-Up. This device telescopes up through the open roof hatch to give you something to hold onto as you enter and exit the roof hatch. (A customized installation is required for a ship's ladder.)
STEP 7 - Locate on floor plan - you will need to tie down the exact location so that the roof opening can be coordinated with roof structure.
STEP 8 - Show on roof plan - positioning the roof hatch on the roof plan helps coordinate everyone’s work, like roof drains, HVAC equipment, roof edge guard rail...
Finally, if your roof has multiple levels, work out how to get to all the levels - more roof hatches, ladders, stairs? After you have designed the first ship’s ladder roof access, each succeeding one will be a breeze. One added step is to remind your client how you are “helping with maintenance” by your thorough attention to design.
* This link to the OSH is intentional. I can’t find any OSHA regulation that applies. The 2012 IBC has this to say:
“1009.14 Ship ladders.
Ship ladders are permitted to be used in Group I-3 as a component of a means of egress to and from control rooms or elevated facility observation stations not more than 250 square feet (23 m2) with not more than three occupants and for access to unoccupied roofs.
Ship ladders shall have a minimum tread depth of 5 inches (127 mm). The tread shall be projected such that the total of the tread depth plus thenosing projection is no less than 81/2 inches (216 mm). The maximum riser height shall be 91/2 inches (241 mm).
Handrails shall be provided on both sides of ship ladders. The minimum clear width at and below the handrails shall be 20 inches (508 mm).”
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Original post date 2FEB14.