Thread: Type of footings for pergola

When we did our carport the advice was to coat the post in oil, stand the post on a brick and then fill the hole with concrete.

If you want it freestanding without bracing on a brick in concrete is best.
If you really want to pure answer your question,its on gal metal stirrups above the ground.
These provide no sway support from the ground so you'll have to brace it every way with straps or timber beefy corners braces
Clive

Also use proper concrete, not quick set. Quick set is not as strong due to the plaster in the mix to make it go off quicker.

Good thoughts thanks.

I have also read about putting a few inches of large gravel in the base of the hole - I assume to allow any water that gets down between post and concrete to run away rather than pool and damage the timber.
Any thoughts on that?

Perhaps post on brick on gravel?

I had considered saddles/stirrups but the shed will have to withstand high winds from time to time so for the extra vertical and lateral stability I thought heavy deep footings wider at bottom with post in ground near a third of its length - with a bolt or 2 through the post down low might do the job.

I really dont want to see it behave like a big aerofoil.

Gravel is good.

Make sure you get treated timber for the posts that is suitable for 'inground' use.
Have a read here:

TIMBER TREATMENTS AND HAZARD LEVELS

When treating timber, there are different levels to which it can be preserving, depending on the hazards to which it will exposed to, based on its application. To understand this better, the different in-service conditions have been classified with a hazard (H) class.

Timber is treated to the relevant H class for its use. The higher levels are protected to a greater degree, and are suitable for use in all the lower level applications also.

H1 – Designed to minimise the chances of an attack by insects and termites, H1 treated timber is best used in well-ventilated places where the timber will be kept off the ground and isolated from weather conditions, including rain or any moisture. Its typical uses are framing, flooring, furniture and interior joinery.

H2 – Similar to H1, H2 is also designed to minimise the risk of an attack by insects and termites, and can be used in well-ventilated places where the timber will be kept off the ground and isolated from weather conditions, including rain or any moisture. H2 however, is more resilient and doesn’t need to necessarily be kept in a well ventilated area. It does however need to be prevented from wetting. Its typical uses are framing, flooring and any other dry situations.

H2F – Also designed to minimise the risk of an attack by insects and termites, H2F must be protected from wetting, and is commonly used for framing (envelope treatment) and used in dry situations south of the Tropic of Capricorn only.

H2S – Similar to H2F and previous levels of treatment, H2S protects timber against insects and termites, but it also allows for subject to periodic moderate wetting. You will find H2S commonly used in the treatment of LVL/Plywood (glue-line treatment) used in dry situations south of the Tropic of Capricorn only.

H3 – The next level of treatment, H3 is suitable for use in applications where the wood is kept off the ground and exposed to weather conditions and periodic moderate wetting. Most commonly you will find this treatment being used in weatherboard, fascia, pergola posts (above ground), window joinery, framing and decking.

H3A – This level of treatment is designed to be applied to products that are predominantly in vertical exposed situations and intended to have a supplementary paint coat system that is maintained regularly. The most common uses for H3A are found in fascia, bargeboards, exterior cladding, window joinery, door joinery and non-laminated verandah posts.

H4 – This is the first level of treatment that is suitable for use in applications where the timber is in contact with ground or is continually damp. H4 is designed to minimise the likelihood of attack by insects, including termites, and radical decay where a critically important end use is involved. Typical uses for H4 include fence posts, greenhouses, pergola posts (in-ground) and landscaping timbers.

H5 – A stronger level of protection, H5 is suitable for use in applications where the timber will come in contact with the ground or fresh water. Other than protecting against the likelihood of attack by insects, H5 also offers protection against extreme decay. Common applications that call for H5 include retaining walls, oiling, house stumps, building poles and cooling tower fill.

H6 – As protection against the highest level of hazard, H6 is appropriate for applications where the timber will be in prolonged contact with sea water. H6 is designed to minimise the likelihood of attack by marine borers and extreme decay. You tend to find H6 used only on boat hulls, marine piles, jetty cross bracing and other similar applications.

Also, use 20MPA concrete mixed before it goes in the hole, as has been mentioned. Don't pull the 'mix in the hole' stunt
Don.

Originally Posted by edddo

Im building a free standing 6 x 4 m pergola with (treated pine) posts at 3m centres (so 6 posts) min 600mm deep, 450mm wide.
What would be the best footing design for the posts to have a long life?
Thanks.

About 25 years ago when we had a second water tank built I decided at the last moment to build some sort of structure on top of it . Because of the rush and lack of planning I just inserted six long bent bolts at roughly the same spacing into the concrete. I then had to come up with a solution to attach the uprights to the bolts. I realise that yours will be a lot bigger
and the only thing in common is the free standing. Because my bolts were not placed accurately I couldn't prefabricate and had to cut every piece of timber individually which was an absolute pain as every piece, apart from the spacers in the uprights has an angle or bevel. If I would build another one I would make it eight-sided and place the uprights very accurately.
.W.

Originally Posted by edddo

Good thoughts thanks.

I have also read about putting a few inches of large gravel in the base of the hole - I assume to allow any water that gets down between post and concrete to run away rather than pool and damage the timber.
Any thoughts on that?...………….
.

I think the gravel is so that the concrete can get down between the large gravel and the base of the post and so seal it from termites. I would also put the cut end of the post at the top and not down in the concrete as I don't think the H4 treatment goes in very deep, if both ends are already cut you can get a treatment to paint on which I have used on fence posts, in that case I
wanted the factory treated ends up in the weather.

If your posts are not H4, Mick's tip of oiling them would help but instead of painting them I would soak them in oil, that way they will absorb much more, I have done this with fence palings and the soaked ones retained the used sump oil much better than the painted ones.