Mostly out of curiosity, and yes a tax payer forced funded pad is best, but

Is there a rule of thumb type math figure for calculating if a roof can successfully handle a helicopter?

Our building permit required a loading calculation for our roof trusses. That loading is in pounds per square foot. If you have that data, it's mostly a matter of determining the weight of the copter and the surface area of the landing skids. Divide the area into the weight and you get a lbs/ft2 number to compare to your truss capacity. We have a steep pitch to our roof, so even if it could take the weight, the copter would just slide off the the concrete below.

If a state, county, or other special circumstances haven't dictated a higher roof load, the minimum design criteria will be 20, 30, or 40 pounds per square foot depending on what snow load zone you are in. You can do a search for a snow load zone map, but it is basically southern states, the rest of the country, and then the tip of the northern states.

From there the math is easy, if planning for a Jet ranger to operate in the middle of the country at a typical weight of 3000#, you're going to have to build a pad of at least 10'x10' on the roof. You will need a pad regardless of the craft or roof load capability in most cases anyway, because you need to get the load spread across the trusses, beams, rafters or whatever load bearing members it has. Almost no actual roofing substrate is designed to be load bearing. Otherwise you will be limited to landing directly across the members only, and that in itself will get pretty limiting as most skids (or worse wheels) don't give you very big foot print. Build a lightweight pad capable of spreading the load and even a manufactured home will carry your bird, our trailers do with less effect than the fuel or water they haul on them as well.

Take care, Rob

A first world problem!

Rob wrote:If a state, county, or other special circumstances haven't dictated a higher roof load, the minimum design criteria will be 20, 30, or 40 pounds per square foot depending on what snow load zone you are in. You can do a search for a snow load zone map, but it is basically southern states, the rest of the country, and then the tip of the northern states.

From there the math is easy, if planning for a Jet ranger to operate in the middle of the country at a typical weight of 3000#, you're going to have to build a pad of at least 10'x10' on the roof. You will need a pad regardless of the craft or roof load capability in most cases anyway, because you need to get the load spread across the trusses, beams, rafters or whatever load bearing members it has. Almost no actual roofing substrate is designed to be load bearing. Otherwise you will be limited to landing directly across the members only, and that in itself will get pretty limiting as most skids (or worse wheels) don't give you very big foot print. Build a lightweight pad capable of spreading the load and even a manufactured home will carry your bird, our trailers do with less effect than the fuel or water they haul on them as well.

Take care, Rob

Thanks!!

That was exactly what I was looking for

I have a steel truss with fabric cover for a hangar. I hang my 185 from it to do float changes. It’s 42’ wide x 36’ deep. 25 lb/sq.ft. is our local code for snow load. 37,800 lb. design load. I never lift the airplane when there’s snow on the roof anyway. Snow hardly ever accumulates. Even if my airplane was at full gross, and again, I don’t change floats with it fully loaded. I try to do it when I’m low on gas.

A light helicopter is nothing compared to the snow load that all buildings are designed for.

But a 10x10 foot helipad on a roof is pretty challenging. Not the landing part – that's easy – but the "getting in and out of the helicopter" part... You want enough room along both sides of the helicopter to walk around (pre-flight inspection, etc.) without any railings. Being able to walk back to the tail boom (both for pre-flight inspection and for tying down the rotors) would be ideal. And if your wife & kids are going to be joining you, a wider "ledge" becomes even more important...

Time for a "war story": When I was stationed in Korea, there was one radar site up on a tall mountain peak, and it had two helipads. One was an actual helipad and was probably 20x20 in size. The second "pad" was actually a paved parking / turn-around area for a Jeep, and was quite a bit smaller. I was tasked to fly one of our OH-58 Kiowas and deliver a mechanic and some parts up to the smaller pad, because a UH-1 Huey had broken down on the "big" pad and they needed to replace something to get it out of there. No problem, I thought. I'd seen that smaller pad before, and knew I would have plenty of clearance to land on it.

Landing on the pad was no big deal, although the pad was only slightly longer than the skids themselves, which meant that the nose of the helicopter was hanging over the end of the pad, as was the aft fuselage. I had no choice but to land into the wind (de rigeuer for pinnacle landings), and that meant that the mechanic had to get out of the front seat, and climb through the back of the cabin to exit on "my" side. The back seat was loaded with his toolbox, parts for the Huey, and some other packages for the radar crew, which made it quite an interesting obstacle course... The fact that the temperatures were in the low teens (ah, winter in Korea!) made it even more fun.

Yeah, I'd be thinking real hard about making that rooftop helipad a bit larger than 10x10 if it were at all possible...

I am expecting pictures of the non happening event

The 10 x 10 example was just for extrapolation purposes of design concept. Oh, and our pads are 8' x 8' +/- and see OH-58, and several 206 variants for traffic multiple time a nigh
Of course they're built to be mobile, and for work, not comfort. And ya, the only real request from the guys when building them was 'make it wide enough to be able to get out and pee )


Take care, Rob