Securing a pergola

[EdF_uk]

Hi everyone,

I’m mulling over pergola design for our garden. Still haven’t decided exactly what we want but one design is basically an L shape around the patio area. I was going to secure the posts into the soil with postcrete, like a fence post. Then we’ll be able to plant climbers that climb up the pergola (see photo)

However, I’m now thinking a more convention pergola might also be good as it will provide more shade - square, 4 uprights type thing. With this there is potential to secure to the patio. I haven’t actually laid any slabs yet and if we do go down this route I’m guessing digging out where the posts will go and filling with concrete will provide the best foundation for the posts. Or is securing to the patio OK too?

Any recommendations would be good. Is there a good guide on the internet. Something similar to pavingexpert?

Many thanks,

Ed

 

[JohnD]

Wooden posts in the ground will rot which is very annoying, and they will be very difficult to get out and replace

A pergola does not have such bad sideways forces as a fence with the wind trying to blow it over, so you can fix it with sockets bolted to concrete pads cast into the ground. Use a simple wooden form round the upper few inches so it will be a neat square. The sockets need to be above ground level and the pad slightly domed to throw off water.

If you use stainless coach screws into plugs in the concrete, or stainless studding cast in, you have a reasonable chance of being able to remove the socket when necessary

 

[Odds]

No need for an overhead structure; the surrounding trellis will support any climbing plant, placed at each end then trained to criss-cross the trellis. Put a parasol in the table for shade. Or plant a tree at the corner of the lawn.

 

[JohnD]

The overhead of a pergola has the advantage that, as well as providing shade, earwigs and bird droppings can fall on you.

 

[Odds]

 

[freddiemercurystwin]

No need for an overhead structure; the surrounding trellis will support any climbing plant, placed at each end then trained to criss-cross the trellis. Put a parasol in the table for shade. Or plant a tree at the corner of the lawn.

Isn't it all about the design and personal choice, some pergolas have overhead joists, some don't, we have a brolly up on the patio, it's great for about 60% of the time, the rest of the day it's useless.

 

[mrrusty]

If there is no roof, there isn't any chance of significant upward forces, so a pergola will stay in place pretty much under its own weight. I did one at the last house on a patio where I drilled some 10mm holes in the slabs, poked a bit of stainless thread bar in with a washer-nut-washer between the slab and the pergola leg, which had a similar hole up the leg. Fixed the thread bar with a bit of silicon (probably unnecessary) , the nut kept the leg clear of the slab so it didn't rot, and it was still very solid when we moved several years later.

 

[Odds]

Isn't all about the design and personal choice...

Yes, it is, and bearing that in mind i looked at the trellis and my first thought was how good that would look with a rose rambling across the whole area, creating a backdrop with colour and impact. A pergola would spread that higher and take away from the display, imo.

 

[EdF_uk]

Thanks everyone. Appreciate your input.

Someone on another forum suggested a sail idea,which I quite liked. I’d be able to put/take down when I wanted then. I’m considering using some pretty sturdy 150mm square posts so securing is pretty key. I understand that installing on top of a concrete footing would be great for replacement and longevity but wouldn’t digging a hole placing a post on a plinth or gravel and filling with concrete, making sure the concrete finishes above soil level be stronger and also rot resistant? Essentially the same concrete foundation but the post is held in the concrete rather than on top. Basically like a fence post.

I’m just thinking that sitting a hefty post on top wouldn’t be strong enough.

 

[JohnD]

also rot resistant?

No

A wooden post in the ground will rot. They will break just above ground level, as rot is fastest where the level of dampness, and the air content, meet to give the ideal conditions.

If it is set in concrete the effort to get the useless lump of concrete out is huge. Professionals therefore often don't bother but dig new holes for the replacements

If you want to set in the ground, use a concrete spur. You can then bolt a wooden post to it, not touching the ground.

 

[freddiemercurystwin]

Or just cast or bolt down a steel support shoe into the top of a concrete foundation and sit the timber post on that, so it's not in contact with the ground. Steel timber post supports are propriety items procured from various places.

 

[JohnD]

Or just cast or bolt down a steel support shoe into the top of a concrete foundation and sit the timber post on that, so it's not in contact with the ground. Steel timber post supports are propriety items procured from various places.

I use them

Fine for a shed or pergola where the loads are principally downwards and the roof structure braces the sides together

But I think not suitable for a fence that has strong sideways wind loads, trying to lever the posts over.

 

[freddiemercurystwin]

It is a pergola thread isn't it?

 

[Mike13]

It is a pergola thread isn't it?

It was, but OP then mentioned a sail, and that leads to a different base choice.

 

[freddiemercurystwin]

Fair enough, maybe the OP should make their bloody mind up what they actually want then and then ask questions relevant to the design.