Thread: Weight Bearing on Double Garage Shed Stick Roof C-Channel Beam

one way to find out post pics of end result so we can all learn from practical rather than theory

Are you just wanting to lift something or do you want to store something? If just lifting you could fix temporary supports either side of the centre from the truss to the floor just clear of the item you are lifting. I have done this on a timber framed roof I had some concerns about.

Best to contact shed designer / supplier for specific advice. Very few of these structures are designed for "additional loads" only for the typical structure loads that it will experience during construction and its designed service life.

Without a bottom chord the lifting capacity is minimal.

Ken’s post above sums it up. If it’s not a triangle, it will change it’s shape when load is applied. Which means it will come towards the load, which means it will come down.

I'm on my second C channel main frame with purlins and girts to support cladding and roof, both fairly large (16m x 12m or larger, 5 main frames 4m apart). Both have had the rafter apex reinforced by 10mm plate inverted broad V's secured to each rafter with 6 or 8 14mm dia bolts. All have been tall enough for me to not entertain the concept of trying to lift off them, I use a pedestrian fork or a gantry for lifting.

From your pics, your rafters appear to be formed from C200 mitred and end welded to a length of 75 x 5 or 6 bar at the apex. Overall strength would be dependent on the quality of the welds and thickness of the C channel wall where welded. One indication of capability would be to look at the apex plate to determine whether the hanging extension is part of the section between the C channels are a later addition. If it is integral with the joining bar, that would indicate that the designers envisaged some possible hanging load in the design, but does not put a value to it, if it is welded on separately, that is an indication that it is a modification made post design phase.

There is not a lot to prevent post spreading at the far end, which would occur if the apex was subject to external loads,, nor is their anything but a bit of strapping to purlins to prevent the rafter rolling sideways under load, so I suspect that ultimately my answer would be that it is not intended to carry any additional loads.

With regard to wind ratings etc, the issue at hand there is the wind passing over the roof and trying to lift it off, not punch it in, so that is a completely different loading mechanism. The climate based item that would relate to a down load being supported by the frame would be snow or ice loading, and with or without climate change issues, that would be unlikely in Brisbane.

One "red flag" to me with this shed is the most unusual orientation of the "C Purlins" as they are in "Girt" orientation or its more likely that they are "top hat sections."

"C Purlins" must be installed vertical - "Z and C Section purlins must have the top flange pointing up the slope to minimise rotation." - from Stratco "Purlins & Girts - Design Guide."

This note is about suspended loads on purlins, not the portal frames,

"Loads to be suspended from roof purlins must be accounted for in design. No allowance is made for this in the Capacity Tables. Any such loadings must be connected to the purlin web by using hangers and/or screws." - Stramit® Purlins and Girts | Stramit

As most shed designers work from the manufacturers span & capacity tables or their software, so typically no allowance for "point loads" unless specifically requested by the customer.

OK from what I am reading I could hoist up a bit of weight maybe 100kg but thats probably about as heavy as I'd want to go. The is a plate welded up the centre of the C purlins.

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Where these purlins meet they seem to be welded pretty well.

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I was doubtful but I would have liked to have been able to hoist up 300kg - 400kg. My best option is probably a 1000kg mobile hoist ($1000) or a 1000kg engine hoist ($250).

I have a new barn and have just completed moving around 20 ton of gear out of storage into it with a ute, a pedestrian fork at the loading end and a H&F 1T gantry system at the unloading end. You haven't disclosed what you want to lift or how regularly you may need to do it, but I found the gantry very useful for the move, and have future use for it for for car engine removal/installation etc. Stuff that I was unloading with it was mainly palletised packing cases and metal cages at around 500 - 700kg, plus heavy individual items. My ute tray is about 1m high, and an engine hoist would not have the height or reach/load capacity to have picked anything off the tray.

Cons to the gantry system are that it is large when assembled and heavy (160kg shipping weight) so is neither compact for storage or easy to assemble/dissasemble manually single handed to make it more compact for storage. Since I have emptied the storage area which I was clearing, and now have my fork in the barn, I may use the fork to partially disassemble the gantry so it can be stacked against a wall and take up less space.

I have previously moved small metalwork factories a couple of times with trailers and and an engine hoist, it can be done but industrial drill presses, welding tables etc can be a challenge unless you have a very low trailer, again an issue of limited height or limited capacity, take your pick. However they do fold into a fairly compact item for storage, or are able to be easly dismantled if needed.

If only need the lifting gear for short time, why not hire a forklift, Dingo or something? sure your big hire places would work out a solution, of course you will probably need it longer.

H and F do a neat mobile gantry at a very reasonable price and it has a 1 t capacity

Thanks chaps - in the last 1-2 years I have embarked on a restoring old industrial quality wood working gear, the longer term goal is to have mainly a workshop with Wadkin kit. I've got 4 bandsaws I've acquired this last year which I'll restore. One being an early 1900s Wadkin DN: Wadkin DN Bandsaw Restore - Early 1900s this saw weights 850kg. I had it delivered door to door and had the crane truck driver put it onto a pallet jack. The other three bandsaws were all picked up by partially disassembling the saws and picking them up with my dads engine crane - they are however closer to around 650kg and went on a pretty low trailer (tray base is about 50cm off the ground).

Anyway a hoist of some sort will greatly help with various things:

Example 1: That Wadkin DN tabletop is a two man lift - at a guess it's roughly 100kg or more. It would be good to have a setup so I can hoist off the tabletop off it's trunnions and lower it onto a trolley to move it around. At some point I'll have the tabletop re-ground as it's putting badly in some areas.

Example 2: Last weekend I had a Wadkin BGY disc and belt sander driven up from Sydney by the seller who was coming up to visit he's family and friends. We managed to get the sander off the back of a Falcon ute by letting the tired down and maxing out the hight of the engine crane - we literally had about 1cm of clearance. The sander weighs about 350kg and will restore it at some point also. Can be viewed here: WADKIN BGY Disk & Belt Sander

Example 3: I hope to acquire a Wadkin PK table saw at some point - they weight closer to 1000kg as far as I know. Sometimes at the buyers end you get lucky and they have a fork lift. Getting it off on my end is the challenge. Anyway you get the point ...

I am extremely short on space in my 2 car shed so ideally my setup would involve hoisting from a cross beam/joist/purlin. I have considered buying some cheap second hand steel I-beams and welding them up with feet to bolt to the concrete slab to make a gantry. I could then hang a monkey and block & tackle off this to get things off the back of my ute or a trailer and down onto a pallet jack. This idea means its stationary and solves one problem only.

So far I have found a car hoist to be very handy - it's mobile and can pretty much take the kind of weights I've had to deal with. BUT as mentioned it's got it's hight limitations. I have an old Hilux with a lift kit there is no way I can get any of the machines I have off my ute with the engine crane.

How high is the door opening? If you are considering a fixed gantry, one as close to the front wall as practical may be viable if you could get the gear that you might bring in under the top of the door either on the ute tray or a trailer. The issue that I see with that is that if you have a double width door, the beam would need to be fairly substantial, the H&F gantry beam is fairly large and it only spans about 2.4m. It carries a load OK but it is possible to twist the beam during assembly, a similar sized beam spanning 4m+ could be prone to twisting under load particularly if provoked by any side loading, which could cause the whole gantry to collapse.

I was unloading in the centre of an 8m tall American Barn with access via a 5m container roller door, my only height limitation was the 3.6m max extended height of the gantry. The chain block and carriage knocked about 300mm off that in terms of clearance. For the sorts of weights that you are dealing with, I would definitely be considering a chain block rather than a block and tackle for the actual lift if you want to be able to work single handed. Block and Tackle gets messy beyond 3 or 4 falls, and that still leaves you with a 250kg to 330kg pull to lift one tonne, and you need to take in 3 or 4 times more cable than the total lift/lower range you need to achieve. A 1 tone chain block will handle the same loads with an effort of about 20kg to 30 kg on the chain, plus the advantage of a holding brake if you need a break or need to move the vehicle from under a raised load.

Thanks - my bad with the terminology, I've recently bought an old school chain block thats rated for 1.5t (not a block & tackle as mentioned) I am busy restoring it which will compliment my eventual vintage workshop.

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Regarding the shed it's two single doors so thats OK - my span would only need to be the width of a single roller door.

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I think all the options I can think of within the shed is flawed in some way or another. Whilst I could rig up something I would always be limited by the height. I think I'll stick with what I have been using to move stuff around etc and that is a engine crane. It folds up and whilst it's cumbersome to move it is on wheels so you have a level of maneuverability.

Speaking of Barn Style sheds I live in suburbia in Brisbane so my dream shed is out of the question:

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