Pergola Structural Strength

[Craig Farrall]

I have recently built out a decking and pergola area in my garden. I must caveat this by saying I am a complete novice DIY'er, but like to get involved.

I have attached a few photos of how this looks currently - but I have concerns about the top bit with the rafters from a structural perspective. As you can see, I have used the timber on the outside of the posts (that were concreted in) using carriage bolts. In retrospect, I would have done this differently and maybe cut a piece out at the top of the post, so that those sit on top, instead of to the side to make it even more secure (hope that makes sense) - however I am reluctant to pull all of this down, especially having to take out all of the nails from the joist hangers.

So even though I could / should have done this differently if I was doing this again, my question is what I can potentially do based on what I have currently. A few ideas that I have thought of are:

• Adding further posts that are concreted into the ground at the back only. Obviously I wouldn't want to do this at the front, as I naturally want to keep the big opening as currently.
• Adding triangular corner pieces. Not sure how I would this exactly, with the timber beams being outside of the posts, but I see quite a lot of pergolas doing this. I am personally not a huge fan of how this looks, but if it helps structurally then I am willing to do it.
• Not sure if this will work, but adding another set of timber beams below the ones currently set up around the whole perimeter, which are attached to the posts - not sure if this will help at all though

Any recommendations on what I can do? I don't necessarily feel like this is going anywhere as everything is bolted in, but for example if I were to hang from one of the rafters, there is movement that is concerning me, hence this post.

This does tie into the same question, but I have attached a picture of the carriage bolts. My question on this is I have had to use one bolt only towards the bottom of the beam, as I have the cross beam also needing to be attached by the bolt too, so I added those more towards the top on those. Ideally I would bolt this up twice at the top and bottom - but obviously couldn't do this as the bolts would hit into each other. So if there is a way I can possible sure this up too, let me know.

Please go easy on any novice mistakes made.

 

[Nozzle]

You could add large serrated washers, I think they're called timber connectors in DIY shops. Gently prise apart each joint shove in a washer an re-tighten.

https://www.toolstation.com/double-sided-timber-connector/p30004

Nozzle

 

[Craig Farrall]

You could add large serrated washers, I think they're called timber connectors in DIY shops. Gently prise apart each joint shove in a washer an re-tighten.

Where would you use those, would this be anywhere where I have bolts at the minute? Will this make much of a difference, do you think?

 

[Nozzle]

You add them between where timbers cross and crushed between the faces. The serrations lock the opposing faces together more than you could achieve with just the bolt/nut alone.

http://medias.pim.simpson.fr/files/...d-jpg-default_zoom/dstc-installed-jpg-jpg.jpg

 

[Craig Farrall]

You add them between where timbers cross and crushed between the faces. The serrations lock the opposing faces together more than you could achieve with just the bolt/nut alone.

http://medias.pim.simpson.fr/files/...d-jpg-default_zoom/dstc-installed-jpg-jpg.jpg

That makes sense. As I only have one bolt running through at the moment (because the sides have one too, so can't use another bolt otherwise they will hit into each other), so is there a possibility of using those, but without the bolt? So for example towards the bottom where the bolt it, I would use one of those, and then towards the top use one, but without a bolt?

 

[Nozzle]

It needs the bolts as the screwing action jacks together the posts/beams so the triangular teeth of the washer dig in to the opposite faces of the timber and lock together.

Nozzle

 

[Odds]

Have you thought about what kind of plants will you grow to cover the frame?