Thread: 11 degree or 22 degree roof?

I guess it's a sheet metal roof? If you want to avoid potential leaks 22 degrees is infinitely better. It's amazing where wind driven rain can infiltrate.

I’d be going 22 so your solar panels are closer to the req’d angle which I understand is roughly the equivalent of your latitude. Brisbane is 27 degrees South.

22 deg with gable vents and whirlybird

I have experienced lots of issues on my pergola in that 22degrees is the least fall i would suggest or the issues with water not having enough fall when it gets to the spouting will drive you nuts . . I now have approx 200mm of fall and with corrugated iron roofing this is barely acceptable .If I had my time over I would use a deeper profile iron.[this lack of fall was pointed out in the final inspection]

I am on the edge of brisbane. I built my shed in 97 as I recall.


My initial application had the minimum 11deg gable roof. Council asked that it be increased to blend into my heritage area. It added very little money. I THINK mine is 15 deg or something.


I would be very surprised if the 11 degree roof does not drain properly. Mine is custom orb but whichever way you go it should be fine provided your gutters are clear.


As pointed out a higher pitch together with some form of roof venting will help a lot with heat. You can get solar roof vents now. I have whirlybirds but if I built now I'd get the powered vents.


Solar is another consideration but given you can get second hand panels now for as little as $5-10 each the mounts are literally dearer than the panels.


The biggest advantage IMO of a high pitch roof is storage. You can shelve etc right up to the pitch. My biggest regret was my 8' walls. Higher walls are not much dearer and both space and heat are incredibly improved.


2c

Besides the execellent advice that you have already received, I suggest that you also consider the possibility of wind damage. In storms, it is mainly the low pitched roofs that are damaged, and the steeper pitches are relatively immune.

As my aviation mate says; its all about the angle of attack and lift-off. The wings of a tiger moth have an angle of attack of 5° and it lifts off at 25 knots. [So do skillion roofs.]

Yes I can imagine, at 11 degrees it might be more prone to lift up whereas at 22 degrees that is harder to create the same low pressure.

I talked to my preferred shed builder today. He says the max they do is 15 degrees so we'll go with that. Hopefully the solar people will adjust the panels slightly with their mounts. For now I just need to get it all priced and submitted to council. Apparently I can't even apply to council until after the house application has been submitted and approved.

What height are the walls?
I would go 22 degrees. If it's a truss it will give you more storage space.

I've forgotten if the walls are 3.6 or 3.8. I think 3.6m. I've assumed it is portal frame but I don't recall actually checking on that.


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Do check. Space frames are much more labor intensive to put up and IMO more likely to fail in extreme circumstances. Bizarrely when I bought they were dearer. The only advantage is they intrude less on your floorspace.


I envy your wall height. That will be a fantastic space.


You can get solar panels for $10 each second hand on gumtree etc. If you can source an affordable rail system consider overspecing your inverter/charge controller or whatever your getting and just expand your system later with second hand panels. They are so cheap the angle doesn't matter. Just cover the roof

Originally Posted by DaveVman

I talked to my preferred shed builder today. He says the max they do is 15 degrees so we'll go with that. Hopefully the solar people will adjust the panels slightly with their mounts. For now I just need to get it all priced and submitted to council. Apparently I can't even apply to council until after the house application has been submitted and approved.

Have a look at the enclosed table, noting it is for Hobart and not Brisbane. You should be able to find a similar table for Brisbane.
How does solar panel orientation affect performance in Tasmania? - Sustainable Living Tasmania

Within reason, variations in the tilt angle do not greatly reduce the electricity output. The complication and cost of tilt adjusting brackets is rarely justified.

For most of Australia solar panels should, ideally, face due North, but there are exceptions:

• In the Hobart suburb of Bellerive (across the River) they should face North, but
• In Hobart the ideal angle is 10° to 20° East of North. (Due to late afternoon shading from Mount Wellington.)

The minimum recommended tilt angle is 10° for two reasons:

• Flatter panels will collect more dirt and grime which will reduce efficiency,
• Water will not run off fast enough and may seep in and damage the electronics.