There are a number of very important factors that you need to take into consideration when planning your shade sails' structure. The right planning steps will ensure that the structure performs the way it should. Start by having the area in mind which you wish to fully cover with the shade. This can either be a paved area, a terrace, courtyard, or even a pool. Once you've identified the area you may either want to setup attachment points which will hoist your shade sail or you may want to add it to your existing structure. In addition there are other things you may want to consider as well.
How the sun moves over that area?
Obviously the sun rises from the east and sets over in the west. But as the season moves on it progresses from being low in the sky during cooler months and higher in the summer. So, the structure needs to be planned so that it provides you with the maximum shade during peak summer months, because that is when you need it the most.
It should have a slight twist
Experts will tell you that shade sails which have a slight twist also known as an architectural hypar effect are the best. This happens when you have fixing points which are created either from brackets or steel posts, located at varying heights, in a way so that the sail is slightly twisted to fit. It goes without saying that it's hard to tension a straight or flat sail correctly and when met with heavy downpour it will hold the water for an extended period of time which puts lots of load on the fixing points. So, its recommended that fixing points be installed diagonally at opposing low and high points in order to create a visually appealing and problem free shade sail layout.
The size of the shade sail
Now in order to properly tension the shade sail it has to have some space between the fixing points and the tensioners as well as the centenary curves which are located on the side of the sail. Larger sails will obviously require proportionally larger tension gaps and curves in order to ensure max tension and maximum longevity. So, the best thing to do is to space your fixing points further from each other, further than the shaded area you want. Generally, the fixing point starts from around 300mm away from a shaded point, but this will vary depending on the sail's size.
Fixing shade sails to existing structures
You need to be cautious when fixing them to existing structure like your home. The reason being that bad weather and often strong winds will increase the load which shouldn't be underestimated. To make sure that the existing structure is good enough to handle these loads consult a builder or architect. If it's fixed to parts of your home we strongly recommend that the sails be removed when the wind starts picking up. Fasten you shade sails with snap hooks so that they are easier to take down.
Benefits of Timber versus steel posts
The majority of experts recommend that people use steel posts or aluminum posts instead of timber for their sail structure. Steel happens to be stronger and will not rot or overly deflect. The rust factor can be further countered by using stainless steel or paint over the metal, or using aluminum. But steel is stronger than aluminum and usually cheaper.
The required footing size will in fact vary quite a bit mainly depending on the structure and the overall height of the post sticking out from the ground. The old conservative principal here is to have 1 third in every 2 thirds out, this in layman terms means that posts that are out of the ground by around 2.4m should also be around 1.2m in the ground. This is a conservative calculation but it is extremely safe and worth considering if you are putting up the posts yourself. The footing also needs to be secure because even the slightest of movement will reduce the ability for the post to properly keep the sail tensioned which reduces the shade's durability. The hole's diameter as a rule of thumb should be 350mm but depth is still a very important factor
Mark T. is a civil engineer and an expert with everything shade sails related. He has put up dozens of these shads in his own home and as well as the homes of his clients. He also runs an online store selling high quality shade sails in addition to a blog where to regularly dispense advice on buying and maintaining shade sails.