How to erect a shade sail?

[allanna]

Hi. I would love to erect a shade sail I recently purchased myself. I have a 5 metre triangle shaped sail. I’m just not sure what steel posts to use.  Any suggestions. Square or round ?  Do I need a heavy gage steel for this project? Any advice appreciated. 

[Jason]

Hi @allanna,

You are right to seek professional advice on what posts to use and how they are installed as the force on a shade sail can be significant. In the Bunnings guide How to install a shade sail, the installation of the three steel posts was overseen by a qualified builder to ensure they were structurally sound. Let me tag @Adam_W for you who might like to offer his experienced perspective.     

Welcome to the Workshop community. We're really pleased to have you join us and look forward to seeing this project and many others around your house and garden come to fruition. Please feel free to post anytime you need assistance or have something to share. 

Jason

[Adam_W]

Hi @allanna and welcome!
Shade sails are interesting things. There is actually a lot more engineering involved in installing them that many people realise & the bigger they are the greater the requirements.
I had an interesting experience a few years back. The place we lived at then desperately needed shade for the deck and sails seemed the best idea. When I started looking into it I found out how complex the area is.
Being an actual sail, albeit a porous one, they can be impacted by an enormous amount of uplift which has the capacity to pull poorly installed or inadequate posts from the ground. In extreme wind these can then be whipped around doing enormous amounts of damage.
When I did some research with local council I found that up to a certain size is allowed without any sort of permit but they must be installed correctly. However they also had a clause which said that if attached to a structure - house, garage, etc. - then full planning & engineering approval was needed.
So maybe check your council web-page for 'exempt & complying' development rules. Last thing you want is council jumping on you after you've installed.

Steel posts will give you the most substantial points to fix to but a wee bit difficult to advise what type of post as there are a lot of variables.
You can use a post or a pole, your choice, as the strength is more about the diameter and wall thickness. I would be looking at a minimum diameter of 90mm (for a square post) with a wall thickness of 4mm however... the taller the post & the more exposed the position the more heavy-duty your post may need to be.
When it comes to fixing your posts down they can either be concreted in-ground - footing size will be determined by soil type & conditions, I'd be looking at around 400 to 500mm wide by at least 600mm deep - or you can buy posts with feet attached and these can then be attached to a concrete slab or suitable footing with concrete bolts.
It might even be worth seeking some professional advice.
Shade sails are one of those projects that aren't overly difficult but do need to be done properly.
Okay, hope this has sort of helped.
Please fire any more questions at us!

[allanna]

Hi Adam 

Thanks so much for your response.  Interesting about permits needed. I would not have thought of that.  However the shade sail would be a stand alone structure.  I think you may be right I will get a quote from a professional.  Looking like a big job.  
thanks again. 
allanna

[dharmesh]

I am in middle of process to build and deck and shade sail over it. Plan was to install the posts that will support deck and long enough to install shade sail on it as well. I had engineer visit for site inspection to draw the plans. He said if I want to install shade sail I'll have to do strip footing. Else normal post holes are enough for deck. 

[MitchellMc]

Welcome to the Bunnings Workshop community @dharmesh. It's amazing that you've joined us, and many thanks for contributing to the discussion.

It's great to hear of your experience installing a shade sail on the same posts as a deck. I'd imagine the engineer called for strip footings as shade sails can exert quite an extreme amount of directional force on their fixings. Whereas a deck by itself is a constant load of downward force. It would be fantastic if you'd like to share the rest of your project with us, and we'd encourage you to let us know if you need any assistance. I trust you'll find loads of inspiration for your decking project within the community as our fabulous members share their handiwork here all the time.

Mitchell

[dharmesh]

Hey @MitchellMc I am still at drawing stage and then council approval and then build. I'll surely keep sharing as I move ahead in the project.