How to reinforce an existing pergola for swings?

[nashadzne]

We built a pergola in our side garden with plans to add two swings/ daybeds later. The pergola measures 4000mm x 3000mm, with six 200mm x 200mm posts and 140mm x 45mm rafters. Our landscaper reinforced the structure with cross-beams at each end and added extra support through the centre (between the two middle posts).

We now want to install two swings facing each other in the positions marked in red in the photos. However, these areas currently only have the standard rafters and no additional reinforcement. The swings/ daybeds we are looking at are 1800mm x 700mm each. What would be the best way to reinforce these sections so the pergola can safely support the swings?

[EricL]

Hello @nashadzne 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about adding swings to your pergola.

Adding a swing to your pergola will add significant weight to the structure while its being used. There are also the dynamic forces that will be applied to the structure of the pergola. Your pergola's structure must be properly reinforced to take on these changes. In this particular instance, I suggest engaging the services of a handy person or builder to assess what needs to be done in order to strengthen your pergola frame.

Generally speaking, I propose moving the swing to the support beams that are sitting on the posts. These would be the best supported parts of your pergola but please keep in mind that this is not enough and additional support will be necessary. For example, angled support braces between the post and beams might need to be added, extra beams to counteract shearing and add structural stiffness to the frame. 

Let me call on our experienced members @Dave-1, @Nailbag and @AlanM52 for their recommendations.

If you need further assistance, please let us know. 

Eric

[Dave-1]

Good Morning @nashadzne 

Your Pergola doesnt have any reall diagonal supports to stop swaying. Which raises the isse before we think of attachment points ( @EricL's suggestion of moving the points of attachment is a good one)

The pergola looks solid but if you imagine a swing arking back and fourth with a persons weight you will get some movement in the structure. We can see 2 bolts used to attach the side rails and then nothing else to stop that lateral movement of the swing. You could install diagonal bracing from post to rail to help firm up the sway factor. But that is every post and both sides would be wiser.

Carrying a daybeds worth of weight on one of those rafters would cause issues, doubling up each rafter carrying the daybed would be a better way to support it. 

Last point is how the posts are attached to teh ground? Is it a concrete footing with a steel plate, or is the post sitting straight in the soil? It will effect the sway ability depending on which it is. 

Dave

[AlanM52]

Hi @nashadzne,

For a start you should not hang off the rafters.

With only those connectors, as @EricL suggested use the main beams.

Rather than brackets I am thinking decorative panels.

Cheers

[Nailbag]

Hi @nashadzne 

Any idea on the weight of each swing?

I'm leaning towards an LVL (Laminated Veneered Lumber) the same length and end angles batten screwed to the ones and using connecting brackets as already used. You could also sandwich them between another on the other side to conceal the colour differences. 

Nailbag

[nashadzne]

Thanks @Dave-1. The orange squares have double beams and the builder recommended attaching the swings to these but we are wondering if we can attach to the rafters in between with additional reinforcement. Also, the posts are on concrete footings. 

[nashadzne]

Thanks @Nailbag. I'm not sure I follow. Are you suggesting that we add the LVL below the rafters? Also, the weight is around $40kg - estimated.

[Nailbag]

H @nashadzne 

I was suggesting sitting on the beams next to them and batten screwed together.

Nailbag

 

[Noyade]

Evening @nashadzne 

I was thinking or fabricating 4 steel anchor 'boxes' that fit between those two rafters which are in turn bolted to the post.

Bolting the two rafters together.

Anchorage at the bottom for a rope or chain or whatever.

Just a late evening thought.

Cheers.

 

[Dave-1]

Good Morning @nashadzne 

I am not really worried about the stationary weight of the chairs, But the weight that will rock as a seat is swung. I am close to 100kgs, another one of me is 100kg plus your estimation of the chair itself. 240kg.... (double that for the second swing) Swing either of those on an ark and all of a suddern you have an imense amount of pressure wanting to take the load out of alignment. Hence the diagonal supports I was refering to. 

The doubling of the beams that @Nailbag and @Noyade mention will help carry a static load, but still I have concerns of that timber wanting to twist as teh seat rocks back and fourth. I have often sat there looking at swingsets and remembering as a kid how the highre we swing the more likely the feet on the opposing side of the swing woukld lift up a little... Kids are just tiny adults and we will swing.

Dave