Adding a lean to shed on

[rooster cogburn]

I would have 254x146x37 suitable for upright and 260x90x35 parallel flange that with a bit of extra work would do the roof structure. I know myself a new truss roof would be better and also let me go slightly wider. Any pens done will be bedded with a scrape passage at this stage anyway

 

[Agri-Eng]

Can get beams different lengths upto 15m.

Depending on the beam size, they can actually be got up to 18.3m in length. See below, even though, it is an old stock list from Duggan Steel, I find it a good reference, as it gives an idea of what can be obtained, even nowadays.

 

[nashmach]

We put up a 45' lean-to this year. All 12x6" steel. I believe roof pitch can also influence the the beam strength required. Ours is 7 degree pitch which is shallow enough.
Would an A roof portal frame not make more sense than raising up the high end? Probably not much difference in the cost.

7 degrees is nearly half of what it should be. It is very shallow, is it pretty sheltered?

I wouldn't like to chance that here.

 

[Barrowsider]

7 degrees is nearly half of what it should be. It is very shallow, is it pretty sheltered?

I wouldn't like to chance that here.

No, an exposed site. We consulted a few different engineering/shed building firms and none had any issue with that slope. It wouldn't have been built if there was the smallest bit of concern from anyone.
Greater slopes are all fine with old 25 foot lean-to's of the past but at 45 foot wide the loss of height makes it impractical. My calculations are open to correction but at 7 degrees the loss of height over 45 foot is 5.6 foot whereas at 12 degrees it's 9.5 foot and at 14 degrees it's 10.75 foot.

 

[Agri-Eng]

No, an exposed site. We consulted a few different engineering/shed building firms and none had any issue with that slope. It wouldn't have been built if there was the smallest bit of concern from anyone.
Greater slopes are all fine with old 25 foot lean-to's of the past but at 45 foot wide the loss of height makes it impractical. My calculations are open to correction but at 7 degrees the loss of height over 45 foot is 5.6 foot whereas at 12 degrees it's 9.5 foot and at 14 degrees it's 10.75 foot.

They say, a picture speaks a thousand words.
It is really only when it is drawn up to scale, one can truly appreciate the actual drop, depending on the required angle.