# Building a rooftop for workshop

Hello.

I posted this last night and after two people replied commenting on regulations, the thread was closed because it was resolved. It wasn't. So I'll post it again but this time I'll start with a comment about the replies I got on the other thread to which I couldn't answer back.

I know that building codes exist for safety reasons, both my own and the other structures around.
The thing is that I did try to find the codes for my region and the only documents I could find, and I don't even know if they contain the information I need (the titles are not as specific as you'd want), have to be purchased, there's plenty of them, and they cost about usd$35 a pop. So I could easily spend usd$1,000 and still not find the answer.

And yes, I also know that when you build a structure you have to submit plans and get approved and later inspected and that's the right way to do it. But this is not an option.
The reason being, there's seldom a house that is 100% up to code where I live. Everyone at some point adds or changes something without getting a permit. The house I live in and the three neighbors I have we all have something that is not 'legal'. Not necessarily in the structure. For instance, one of my neighbors has their backyard covered with a roof (similar to what I want but much smaller and lower) and the space between the ledge of the roof and the wall that separates us (about 30cm height) has sliding windows panes. Now, I have no idea why, but those windows are 'illegal', not the space or the fact that you can stand on a chair and look to your neighbor. Having windows instead of an open space is the 'illegal' part.

And so it goes for some other stuff. So, if I were to submit plans and then get inspected, it will be a dang storm of problems not only for me but for my neighbors as well, because the inspector will most certainly take note of all the issues around and screw everyone. Also, this would take a LONG time, and that's something that I don't have. I have to get this done before the rain starts (it's autumn here now, and winter is coming)

Is it 'wrong'? sure. Is it 'illegal'? fine. Can I do something about it? no.

That's why I came here, to get an answer from people who know their stuff, I never mentioned that I want to build out of code, but code is not physics, I want to do it as right as I can (as I mention below), but I can't do it legally. If I thought that the code was just crap and said 'I know what I'm doing', then I wouldn't be here, looking for the right answers and some help to keep safe.

So please, I'd appreciate if we could stay on topic and disregard the part about building codes and regulations and permits because that just won't help.

Also, I'd like to comment that I am a welder and woodworker and that's what the workshop is for, so I can work throughout the year (last year I lost several weeks of work because of the weather and that cost me a lot). So to some extent I do know what I'm doing, but this is a big roof for a big space and it's a lot bigger than anything I've done before (like a roof for small driveway, where I don't really have to worry about it collapsing under its own weight)

Thank you in advance for taking the time to read this and hopefully provide an answer or useful information. Sorry about the post being so long. The above was needed for clarification and below I was as detailed as I could possibly be, measurements and weights are provided in both metric and imperial to help you move along faster.

Thanks again.

I've been looking for hours and can't find the information/formulas to figure this out, that's why I came.

I'm building a roof for the backyard (workshop) so I can work all year regardless of weather conditions. I know what materials and dimensions I could use to be 100% safe, but I still want to know if I can get away with using less (or different?) material and maybe stretch distances a bit, in short, save some material and some money. So i want to be safe and do things right but not over do it and over spend.
So here's the rundown. I'm going to be as specific as I can.

The space is 38.64 mt2 (416 ft2) in a trapezoid shape with dimensions 8.4x3.3x8.5x4.6 mts (27.5x10.8x27.8x15.1 ft). naturally the floor needs to be clear, so only supported by the sides, no columns.

On the 8.4 mts side it's my house, 4.4 mts (14.4 ft) wide and in the middle of the workshop, so 2 mts (6.5 ft) clear to either side of the house (the ends will have a column down to the floor (concrete). the height (where the structure will be anchored) is 3.5 mts (11.5 ft).

On the opposite side is the wall with my neighbor, all 8.5 mts and it's 3 mts (9.8 ft) in height, so rain will run this way. The structure will be sitting on this wall but I'll still run some columns down to the floor, although the weight will be supported at the top. The columns are so I can hang some shelves and cabinets. Can't fasten or anchor anything to the wall.

On either side it's clear, so columns will be added where needed.

I'm going to use steel profiles (rectangular and square) for the structure. I'm using polycarbonate sheets as roofing material (the wavy kind).

To the house (brick, pretty strong) I will be anchoring an 8.5mts long profile to support the beams that will run across the space and rest on the neighbor's wall. These beams in turn will support the other 8.5 mts profiles that will run along the space to which the roofing will be fixed. I don't know the terminology but I think the closest to these longitudinal profiles is joist, so that's what I'll call them.

So here's my issue, how many beams will I need to support the joists and how many joists will I need to support the roof, using as little material as I can without compromising safety.
This is the information I haven't been able to find, how much weight can a specific steel profile support, giving the details of said profile. Or, what profile will I need to support the total weight, which is roughly 120kg (264 lb) for the beams, joists and roofing (according to an earlier design I made where all material is accounted for). It's neither too rainy nor too windy where I live (Santiago, Chile).

Profiles dimension are probably different from what you have available. But this is what I have to work with.

I'll be using rectangular profiles for the beams, I was thinking that 50x20mm (1.9x0.78 in) should be good, material thickness can be either 1.5mm or 2mm (17 and 15 Ga, if I'm reading the chart correctly). 1.53 and 1.99 kg/mt (1 and 1.34 lb/ft) respectively.
I would like to use 1.5mm if I can, although the price difference is not that much, everything adds up.

For the joists I'll be using square profiles. I thought about using shorter pieces in between the beams but that's going to take forever, so I opted for long joists the entire length, sitting atop the beams (they will be fixed together).
I'd like to get away with using 20x20x1.5mm 0.83 kg/mt (0.78x0.78 in x 17Ga and 0.55 lb/ft) ideally. Other options are:
25x25x1.5 1.06kg/mt (1x1 in x 17Ga 0.7 lb/ft)
30x30x1.5 1.36kg/mt. (1.18x1.18 in x 17Ga in and 0.9 lbs/ft).

I don't think 2mm (15Ga) is necessary for this because it's not really load bearing (that's the beams). It's mainly a place for the polycarbonate to sit on straight and be fastened.
The weight of the Poly is about 41kg (90 lbs).

So with those numbers in mind I was thinking that 8 beams (1 on each end and 6 spaced in between) equally spaced 1.2mts (4 ft) apart, and 5 joists (1 on each end and 3 equally spaced in between, about same separation as the beams) should be enough?

Nothing will be hanging from this structure other than some LED light panels, which are very light but I can't find the actual weight. Also it won't be stepped on unless some burglar decides to go roof hopping, which is not really going to happen.

So I think that is it!

Any help would be much appreciated and thank you for reading this far!

Rod.

## Answers and Replies

Homework Helper
2022 Award
Building codes exist for a reason.
Badly constructed buildings become projectiles in a storm.
Don't be a selfish idiot.

davenn, Vanadium 50 and russ_watters
Mentor
I know that building codes exist for safety reasons, both my own and the other structures around.
The thing is that I did try to find the codes for my region and the only documents I could find, and I don't even know if they contain the information I need (the titles are not as specific as you'd want), have to be purchased, there's plenty of them, and they cost about usd$35 a pop. So I could easily spend usd$1,000 and still not find the answer.

And yes, I also know that when you build a structure you have to submit plans and get approved and later inspected and that's the right way to do it. But this is not an option.
The reason being, there's seldom a house that is 100% up to code where I live. Everyone at some point adds or changes something without getting a permit. The house I live in and the three neighbors I have we all have something that is not 'legal'. Not necessarily in the structure. For instance, one of my neighbors has their backyard covered with a roof (similar to what I want but much smaller and lower) and the space between the ledge of the roof and the wall that separates us (about 30cm height) has sliding windows panes. Now, I have no idea why, but those windows are 'illegal', not the space or the fact that you can stand on a chair and look to your neighbor. Having windows instead of an open space is the 'illegal' part.

And so it goes for some other stuff. So, if I were to submit plans and then get inspected, it will be a dang storm of problems not only for me but for my neighbors as well, because the inspector will most certainly take note of all the issues around and screw everyone. Also, this would take a LONG time, and that's something that I don't have. I have to get this done before the rain starts (it's autumn here now, and winter is coming)

Is it 'wrong'? sure. Is it 'illegal'? fine. Can I do something about it? no.

That's why I came here, to get an answer from people who know their stuff, I never mentioned that I want to build out of code, but code is not physics, I want to do it as right as I can (as I mention below), but I can't do it legally.
This is not an approach we can entertain. Period. We can't stop you from building this structure yourself, of course, but we cannot provide you with illegal advice. And yes, basically anything we do to help you here would be illegal. Thread closed; do not re-post it.

anorlunda and hutchphd