# Forum Home Renovation Decking  Joist Hanger Load Capacity

## dim

Hi All,  
I'm building a deck with 140 x 45 joists. I'm using Pryda joist hangers FB45120. Does anyone know how much weight this hanger can typically take before it fails structurally if using MGP10 treated pine for both joist and bearer?  
Thank you.
dim

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## ringtail

Nothing on the pryda website ?

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## paddyjoy

As ringtail said it's all in the technical docs http://midstatehardware.com.au/forms...uly%202010.pdf 
Depends on a number of factors such as timber strength, screws vs nails, length of screws also (you can get an extra 15% capacity by using 45mm screws instead of 35mm) etc....

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## OBBob

What are you planning to put on the deck??

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## dim

Hi Paddy, going by page 15 of the Pryda doco and assuming the joint is JD5 then the capacity would be 6.4kN. Which is about 640kg load hanging off right at the joint before it fails right? Thats alot of weight being held up by 6 screws.

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## dim

ObBob, I'm not planning anything heavy other than a small teak table and a couple regular timber chairs. Just like to be sure that it will hold up the weight of me and mrs because she is a heavy.

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## OBBob

> Hi Paddy, going by page 15 of the Pryda doco and assuming the joint is JD5 then the capacity would be 6.4kN. Which is about 640kg load hanging off right at the joint before it fails right? Thats alot of weight being held up by 6 screws.

  But you need to consider more than just static loads. Someone jumping (or falling over) is a significantly higher load than just standing there. These brackets work on the load being perpendicular to the fixing, which how they get those high strengths.     

> ObBob, I'm not planning anything heavy other than a small teak table and a couple regular timber chairs. Just like to be sure that it will hold up the weight of me and mrs because she is a heavy.

  You could add additional joists if you are concerned or use a bolted ledger below the joists if the configuration allows.

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## paddyjoy

> Hi Paddy, going by page 15 of the Pryda doco and assuming the joint is JD5 then the capacity would be 6.4kN. Which is about 640kg load hanging off right at the joint before it fails right? Thats alot of weight being held up by 6 screws.

  Yes but as Bob mentioned this is for a dead load and assumes you are using the hanger as designed. Considering you have one on each end that doubles the capacity to 12.8kn. I imagine the timber will break before the hanger does. 
If installed correctly the screws are very strong, each one has a shear strength of about 7kn and you will have 6 of them.

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## dim

Ok. Comforting to know it can take that sort of load. With joists at 450 centres and spanning 2 metres sounds like I can walk on safely.  
I did see a youtube vedio showing stress testing of similar joist bracket and it did fail with the screws pulling out and splitting the bearer, but they didnt show how much pressure was applied at that point. 
Thanks all for your input.

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## ringtail

You could always build the traditional way and put the joists on top of the bearers.

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## Marc

It would be easy to test. Joint two timbers low on the ground, one end with the joist hanger and the other end on the ground.  Drive over the joist using a plank at different points from close to the end that is on the ground to closer to the joist hanger until it snaps. 
The numbers would be very basic to work out. 
Alternatively drill 3 12mm holes in two pieces  50x50x5 galvanised angle and fix with 12 mm bolts ...  :Smilie:

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## usedbydate

another part of the equation to consider is span and spacing , that is the span of the joists (as advised to be 2 metres@450 centres, and the unknown factor at this stage,  the spacing of the supports for the plate or bearer used to support the joists, which will increase in depth  relative to support spacing, if you are worried about the load then also consider the rotational influence across the joist  simply stiffed using solid blocking or the good old fashioned herringbone bracing   , there are a multitude of choices today  posi struts  etc etc etc

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## DuckCommander

Quite a bit of misinformation here... The number 6.4kN is the ultimate design capacity for A joist hanger. Factored loads must be equal to or less than this value. In this instance the load combination of 1.2G + 1.5L is the dominant load case, 1.2 x dead + 1.5 live. Residential decks must be designed for 2kPa live load. You can back calculate what your loads can be from there if you know span and spacing. If they are 2m total span (support to support) with 450 joist spacing you get 6.4kN / (1m x 0.45m) = 14.2 kN/m^2 (kPa). You typically allow 1kPa for dead design load (100kg/m^2), factored by 1.2 gives 1.2kPa. Subtracting from 14.2 gives 13kPa for live load. Un-factor that (divide by 1.5) gives 8.7kPa or 870kg/m^2 (more than four times more than required 2kPa). So unless you take up polygamy and are octa-stacking heavy wives you're not going to see any structural failures. Side note, this is not actually so simple, we can increase this capacity with load sharing the love between members (joists, not your mates :0). Looking at spans and ignoring joist strength (as per OP) we can see what allowable span we can get with standard loading via [14.2/(1.2x1 + 1.5x2)] x 2 = 6.8m. So you're all sweet.

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## Marc

What was the joke about the engineer again? ... "All you said is factually true but virtually useless" ... ha ha  :Smilie:

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## METRIX

Skew nail the joists to the plate first,for 140 put 5 nails per side, then fit the hangers after, gives a much stronger join,

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## ringtail

Bloody hell Metrix, more nails than timber  :Biggrin:

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## METRIX

> Bloody hell Metrix, more nails than timber

  That's why my stuff stays together, haven't lost a deck yet,  :Biggrin:   :Biggrin:   :Biggrin:

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## ringtail

Using gal gun nails I hope  :Biggrin:  ? It's all I ever buy but I've never seen any else buy them, ever. And yet, they are the nails that are meant to be used with all T2 and H3 product AFAIK

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## METRIX

Always Gal for outdoors or T3, but gee they are pricey, T2 you can use standard steel nails, according to Hyne the treatments don't affect regular steel fixings.

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## ringtail

That's good to know. Was a time up here, not that long ago when bright nails were frowned upon but no one cared as gal were 4 times the price. Lots and lots of guys still use brights outdoors. I don't go through enough to care about the price difference so buying gal is fine for me and I get piece of mind. Customer ultimately pays anyway so I always try to go for the better option in everything.

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## METRIX

> I always try to go for the better option in everything.

  Same, I always go for the Gal irrespective, because most my stuff is outdoors anyway, so no point having bright versions.

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## intertd6

> Skew nail the joists to the plate first,for 140 put 5 nails per side, then fit the hangers after, gives a much stronger join,

  i find a real timesaver is to nail the hangers to the face of the member using a joist off cut as a template, then slide the joists into place & it can be a one man job. Saves on the skew nails, I use HT gal nails in a coil nailer.
inter

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## ringtail

> Same, I always go for the Gal irrespective, because most my stuff is outdoors anyway, so no point having bright versions.

  Maybe if all the paslode fan boys stopped buying the gas / bright nail combos and bought the gal instead the price would come down.  :Biggrin:

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## METRIX

> i find a real timesaver is to nail the hangers to the face of the member using a joist off cut as a template, then slide the joists into place & it can be a one man job. Saves on the skew nails, I use HT gal nails in a coil nailer.
> inter

  Good idea that can be easier, I skew the joists in first so the joint is tight and solid, the hanger then acts as a reinforcement / backup, this forms a very strong join which can never really come loose, it is more work though. 
 I know the hangers will do the job perfectly fine on their own, but I feel more confident in the join skewing the joist first.

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