Thread: Doubling the thickness of Pergola Beams?

Originally Posted by Measure twice!

I recently replaced some pine timber beams on my old pergola. These were pine 190 x 35. I replaced these with 190 x 45 H3 pine thinking this would give less sag with the Jarrah rafters on top.

Alas in the guts it's starting to sag a bit. After doing some research I realise that the span is probably too great being 5400 total length and 3950 from post side to post side.

My questions are

1. Could I bolt on another 5400 length of 190 x 45 to increase the strength and stop sag?

This will help a bit, but not much. Your eye can see a sag that, structurally, is no big deal especially as you wont (at least I hope not) be walking on the pergola roof

if any has anyone has other ideas I would love to hear them.</U1>

one option is to reinforce the underside of the rafters with a steel or aluminium strap (but you will need to get the sag out first)


ian

Thanks Ian.

Any thoughts on those knuckle plates that join timber?

My preference is the scarf joint

Originally Posted by Measure twice!

Hello.

My first post. I am seeking some advice as basic as it may appear. I recently replaced some pine timber beams on my old pergola. These were pine 190 x 35. I replaced these with 190 x 45 H3 pine thinking this would give less sag with the Jarrah rafters on top.

Alas in the guts it's starting to sag a bit. After doing some research I realise that the span is probably too great being 5400 total length and 3950 from post side to post side.

My questions are

1. Could I bolt on another 5400 length of 190 x 45 to increase the strength and stop sag?

2. If so I have a few 3600 lengths. What would you recommend "If it is possible to use them" to join them together. I've been looking at Knuckle plates and then possibly bolting on the 2 joined pieces of timber.

3. If 1 & 2 are not an option do you think a length of 240 x 45 would do the job?

Or if any has anyone has other ideas I would love to hear them.
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The other pic shows where the rafters were nailed onto the verandah this is also starting to sag in between the posts this is Jarrah 140 x 50. I was thinking of putting a length of 190 x 45 or 240 x 45 to deal with the pergola load....Any thoughts?

Regards Ash.:confused:<o> "Looks like the pics are uploading"</o><u1>
</u1>

all disclaimers etc....

personally I would use the 3.6m lengths, but centred with 2 joins on either end, so the sag in the middle is against solid timber - the joiners should be fine especially if you nail laminate the whole length of timber with staggered nailssay 300mm apart (top, bottom,top ,bottom etc).

I suspect that using 2 of the 4mm steel plate joiners about 300mm long and having a 3.6m length plus a 1.8m lengt would also do the job as long as there is decent lamination of the 2 beams together - both then rely on each other - of course make sure the beam is dead straight before lamination by propping.

What about sticking a post in the middle of the existing beam?

Thanks pharmboy2 & Echidna. I'll give the joining of the two timbers a ago above the verandah. As for the post unfortunately it's bang where I was going to put the outdoor table.<o></o>