# Forum Home Renovation Decking  Bearer/Joist Span Help (90x45)

## diyrio

Hey guys, 
Can someone let me know if the attached image is OK for a low to ground deck with no roof?  
Finished deck will be 250mm above ground on house side and then 300mm at the side furthest from the house, so I don't have a lot of height to work with. 
Bearers will be 2/90x45 MGP10 TP with stirrups set in concrete. Joists will be 90x45 MGP10 TP. 
Decking is 90 x 19 merbau. 
I want it to be a solid deck with no bounce, but I don't want to over engineer it if it isn't needed. 
Any input is greatly appreciated  :Smilie:

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## Moondog55

That's a big span for a 90mm deep bearer, if this was my deck I would be using 140mm deep or decreasing the span by using more stumps. Better qualified folk may be better positioned to offer other opinions

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## METRIX

No good, for those spans you need 2 x 140x45 as the intermediate bearers, and 1 x 140x45 as the end bearers, or you could use 2 x 90x45 as the end bearers. 
Remember intermediate bearer is taking load from both sides of the joists.

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## diyrio

Thanks for the replies guys. So if I wanted to use 90 x 45 bearers (laminated) what spans should I be aiming for? The reason for using 90 x 45 is due to the limited height, and wanting to have the joists on top of the bearers for ease of framing up (can keep the bearer next to the house away from the wall for termite inspections) 
Would adding one more stump/stirrup to being the bearer span to 1278mm be good enough?   
Thanks heaps!

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## Moondog55

It's about how far a 90mm depth can span safely and with minimum deflection. I just looked up the bearer tables for floor loads only [ 40kg .m>2] and you can use 90*35 doubled; I was surprised at that myself; but I wouldn't. You did say you wanted minimum bounce. Remembering that the span tables are minimum standards not best practice. Could you add another set of stumps to get the span closer?
What is the difference in your cost between 90*35 and 90*45 in H3?

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## diyrio

> It's about how far a 90mm depth can span safely and with minimum deflection. I just looked up the bearer tables for floor loads only [ 40kg .m>2] and you can use 90*35 doubled; I was surprised at that myself; but I wouldn't. You did say you wanted minimum bounce. Remembering that the span tables are minimum standards not best practice. Could you add another set of stumps to get the span closer?
> What is the difference in your cost between 90*35 and 90*45 in H3?

  Yeah that's the issue I've got...I can build according to the span tables but I'm worried it will be bouncey. I was hoping someone who's built a deck using 2/90x45 bearers and 90x45 joists would be able to tell me what spans I need to keep bounce at a minimum. I can definitely add another stump/stirrup, I just don't want to over engineer it if it doesn't need it.  
---------edit---------  Attachment 121259 
Priced up 140x45 but cost wise it's still cheaper to go with 2/90x45 bearers so here's what I'm proposing ^ 
Bearers: 2/90x45 TP MGP10 sitting on stirrups every 1065mm (with a bag of concrete per stirrup - firm clay here) 
Joists 90x45 TP MGP10 spanning 1335mm spaced at 450mm centres 
Can anyone let me know if that will make for a deck with no bounce?

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## Moondog55

Why 90*45 and not 90*35? It's the depth that counts there not the width. I'll let a real tradesman answer that last question

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## diyrio

> Why 90*45 and not 90*35? It's the depth that counts there not the width. I'll let a real tradesman answer that last question

  2/90x35 MGP10 can span max 1100 with a FLW of 2400 whereas 2/90x45 can span a max of 1300. So I figured it would help with reducing bounce

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## Marc

You figure right of course. 
A piece of timber can carry load according to the shape and volume of wood you have between two supports. Given the same hight, the width is the variable. The thicker the more load it can carry. 
90x140 will carry more than 90x25 ...  :Smilie:

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## Sandshoes

Have been watching this thread as I am about to start the same sort of project however have a little less room so plan on using joist hangers to make things a little easier. 
The only problem I can see with this option is I wont be able to cantilever the joist to set the initial bearer back from the building.  
Is a joist hanger strong enough to have say a 150 joist piece only supported on one end so I can set the bearer back or is there another way around this? Notch the bearer and joist to sit flush for example?

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## Marc

The joist hanger does not work like that, it can only take vertical load so you need one at both ends. 
Can you dig out some room for the bearer close to the house so that you can have that one lower? Drainage will require some thought of course.
The only way a 150 cantilever like that could work is by using blocks of hardwood bolted with an axial bolt near the top and two angle bracket in the centre. This would impart a torsion force to the bearer and you will need to counteract that with proper bracing or use the joist for that and screw the head of the joists against the bearer with long screws end grain. 
Way too much trouble.
Or ... you could have a stirrup for each of the little bits of joist

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## Sandshoes

Thanks Marc!  
Having the bearer closest to the house set lower is a great idea! Will have to dig a slight trench but nothing extreme.  
Best to do all of this frame work in 90x45 h4 pine I would guess, a bit of a google shows the this size in h4 seems hard to find so Im guessing the big green shed wont have it and I will have to go to a timber yard and maybe special order? 
Thanks again for your advice and sorry for hyjacking your thread diyrio

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## phild01

> Best to do all of this frame work in 90x45 h4 pine I would guess, a bit of a google shows the this size in h4 seems hard to find so I’m guessing the big green shed won’t have it and I will have to go to a timber yard and maybe special order?

  The only place I have found H4 is at Mannering Park which I believe is a Mitre10.
This is his ebay listing though it is only F5. https://www.ebay.com.au/itm/90x45-f5...EAAOxyPLpRfelc 
Be worth speaking to Doug.

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## METRIX

> Why 90*45 and not 90*35? It's the depth that counts there not the width. I'll let a real tradesman answer that last question

  Both width and depth matter, the difference between the same depth, say MGP10 - 90x35 vs 90x45 over the same span is around 15-20% more capacity on the 45mm piece.

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## METRIX

> Have been watching this thread as I am about to start the same sort of project however have a little less room so plan on using joist hangers to make things a little easier. 
> The only problem I can see with this option is I wont be able to cantilever the joist to set the initial bearer back from the building.  
> Is a joist hanger strong enough to have say a 150 joist piece only supported on one end so I can set the bearer back or is there another way around this? Notch the bearer and joist to sit flush for example?

  No, the joist hangers must work in pairs, one at either end of the timber, they work on downwards pressure, a cantilever requires a backspan from the timber being cantilevered, ie the cantilevered joist must be one continuous timber, see pic below for explanation.

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## METRIX

> Yeah that's the issue I've got...I can build according to the span tables but I'm worried it will be bouncey. I was hoping someone who's built a deck using 2/90x45 bearers and 90x45 joists would be able to tell me what spans I need to keep bounce at a minimum. I can definitely add another stump/stirrup, I just don't want to over engineer it if it doesn't need it.  
> ---------edit---------  Attachment 121259 
> Priced up 140x45 but cost wise it's still cheaper to go with 2/90x45 bearers so here's what I'm proposing ^ 
> Bearers: 2/90x45 TP MGP10 sitting on stirrups every 1065mm (with a bag of concrete per stirrup - firm clay here) 
> Joists 90x45 TP MGP10 spanning 1335mm spaced at 450mm centres 
> Can anyone let me know if that will make for a deck with no bounce?

  From the specs above which are 2 x 90x45 bearer spaced at 1065mm and 1 x 90x45 joists @ 1335mm the bearer will expect around 1mm of deflection so this is fine, the joists at 1335 will expect around 2mm deflection this is also fine, the deck will feel solid. 
I would consider using 140x45 and using hangers in between them to make it simpler to build, and less holes to dig in the ground.
The price difference can't be that much as you will get longer spans from the 140.

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