# Forum Home Renovation Decking  140 x 45 H3 MGP10   or   140 x 35 H3 MGP10

## Rompastompa

Hi guys,    I posted this in another thread but thought it might be better to start a new one. 
The below refers to MGP10 H3 Grade treated pine timber 
I designed my deck using 140 x 45/2 for the bearers and 140 x 45 for the joists and was all good to go until I thought if I could save a little on the timber and go slightly smaller. 
My plans currently have three bearers running parallel at 1600mm centers apart, and are continuously supported with stirrups at 1520mm, and joists are at 430mm centres with a single span of 1550mm. 
Now to save $150-200 (i understand this isn't much but everything helps)  I have toyed with the idea of going 140x35/2 for the bearers and 140 x  35 for the joists. 
My tabma spans table show that 140x35/2 bearer is good for (2400mm at  1.2m FLW) and (1700mm at 2.4m FLW), and as my continuous span is only  about 1520, it 
should be good right? as its just over 1.2m but not as large as 2.4m? 
For the joists my span table shows a single span for the 140x35 to be 2400mm, where I'm only going to 1580mm. 
Below are the plans, rough at the moment because I just did a quick change of timber sizes so thats why it doesn't marry up. 
Many thanks   
RS

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## pharmaboy2

45 wide for joists  is better for nailing/screwing- that extra 10mm of width when putting decking boards on makes a difference, especially under the join of 2 decking boards. 
second, most common span designs, check what the minimum is and go one size up from there -  minimums provide too much bounce

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## Rompastompa

Phramaboy2, thanks for your response, I will be using hidden fasteners and there will be no butt joints to deal with. 
Also, not sure what you mean by minimum? Checking the guides, maximum for 1700mm joist span (single span) at 450mm centres is 120 x 35 MGP10 and for bearers 120x35/2 at 1200mm FLW gives you 2100mm continuous span between stumps and 2400mm FLW gives you 1500mm continuous between stumps. 
RS

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## ausdesign

AS1684 N3 wind catagory
Low deck - external bearers 2/120*45 = 2.4 single & 2.7 continuous. Internal bearer = 2.2 & 2.4. - 120*45 joist = 2.2 & 2.6
High deck - external bearers 2/120*45 = 2.0 & 2.0. Internal bearer = 1.7 & 1.7 - 120*45 joist = 2.2 & 2.2

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## Rompastompa

Thanks Ausdesign, 
So if I go with 2/140 x 35 for bearers and 140 x 35 for the joists I should be good? as 120 is harder to find around here. 
RS

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## ausdesign

Yes - nail laminated bearers.

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## Rompastompa

Thanks Ausdesign, 
I will be using bolts to laminate the bearers as I have about 30 left over from a previous job and I dont plan on getting nails. Will be using 12g type 17 screws for the hangers. 
RS

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## David.Elliott

I don't believe 10 per bearer will be enough? Nailing distance is usually 2 x bearer height apart and staggered... 
Somebody with more knowledge than me will be along though...

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## Rompastompa

Thanks David, 
 There will actually be more than 10 per bearer when I think about it (sorry should have said this earlier) there will be brackets bolted at each end with 3 bolts, then you got 2 bolts per stirrup, thats another 8, so it worked out it would have a bolt about every 300-350mm along the length alternating high and low, sorry should have mentioned this :| 
 RS

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## David.Elliott

No need to apologise, you may (or may not) be surprised by some of the Qs we get on here...so some of us automatically go to the WCS...(Worst Case Scenario)

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## Rompastompa

Thanks David, 
Greatly appreciate your advice. Now its time to start buying... 
RS

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## Optimus

I'd still nail it.

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## Rompastompa

Thanks Optimus, what size nails would you recommend going into 2x35mm at an angle? 
RS

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## METRIX

If your building a deck of approx 3.2m x 5.3 m and your worried about saving $150 by dropping your timber dimensions, will only result in a bouncy deck with more flex in the joists, bearers and connections.
Sorry to say, to try to save $150 in the scheme of things doesn't warrant a reply to the question in relation to appropriate timbers. 
When you look at AS1684, they quote a timbers MAX span, any decent builder won't build to a timbers Maximum capacity, there are a few notes that go with 1684 tables shown below, see Note 1, which is a miserable decking mass of 20 kg/m2, all my decks are designed with a rating of 62kg/m2, for various reasons, these decks feel solid with no noticable bounce, decks need to be rated higher as they are in harsh environments, unlike internal flooring which is completely covered from the weather. 
The problem with static span tables is they don't take into account deflections in the timber from Live loads, which if not built correctly will result in a deck which has a lot of movement in the Bearers and Joists, this results in a deck which doesn't "Feel" Solid, this puts a lot more stress on the joints as they are continuously moving putting more stress on all the fixings eventuating in fixings which become loose,. 
Total deflection in my decks will usually be 3mm MAX from the Joists and Bearers combined, It's quite common to see decks built which have 8mm deflection in the joists alone, add to that the bearer deflection and you have a dodgy deck. 
I have built many decks and won't compromise the quality of construction  for a saving of a few hundred $, the last deck I built the PCA  commented, he hadn't seen a deck built as strong for many years. 
NOTES
i) Maximum Deck Joist Span is based on supporting a maximum decking mass of 20 kg/m2
ii) Cantilever shall not exceed 30% of the actual backspan.
iii) Joists crippled over supports must be considered as single span joists.
iv) Where joist size D/B > 4 restraint may be required. Refer Clause 4.2.2.3

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## Rompastompa

Dear Metrix, thank you for your comments. 
I understand where you're coming from but I dont believe I am building to max capacity. 
The bearers are supported at 1.5m centres, and spaced 1.6m apart
Based on the above, my tables show that
2/140x35 at 1.2FLW is 2.4m centre to centre on the supports, and
2/140x35 at 2.4FLW is 1.7mm centre to centre on the supports. 
Given my FLW for the intermediate bearer is lets say 1.6m, I'm 0.4m over the 1200 by 33%, but 0.6m under the 2400 by 66% 
My table for the joists, 140x35, show 2.4m max span  at 450mm joist centres. (my spacing is slightly less, at 430mm) 
Mine will be under 1.6m so only 66% of the max. 
Either I have misunderstood or the details I'm reading are inaccurate. 
RS 
P.S Unfortunately I have already ordered the timber and it will be delivered early tomorrow morning, however I have checked off cuts and I can actually add an additional joist to both sides, making the joist centre to centre spacing of 395mm

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## METRIX

Your spans are ok for the above figures, make sure to notch the bearers into the posts, wherever your using double bearers, notch them onto both sides of the posts leaving a 35mm gap in between the two.
Block this gap with 35mm offcuts nailed on, then bolt through the lot, also bolt all post to bearer connections. 
Make sure to run blocking through the middle of the joists and either a perimeter beam to pickup all the joist ends, or block these out, 140x35 will want to roll over easily, personally I don't like 35mm timber as the nail guns tend to blow it apart.

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## r3nov8or

> Thanks Optimus, what size nails would you recommend going into 2x35mm at an angle? 
> RS

  You don't have to nail at an angle, but should use a nail longer than the 70mm total width, and then 'cramp' them over at the exit so they can't pull out

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## Rompastompa

Thanks guys. 
Metrix, couple of questions
1) when you say blow out the timber, i presume this is from nailing into the end grain?
2) for the perimeter beam to pickup all the joists, what does that exactly mean?
3) when you say "or block these out", i presume this is just adding extra blocking to the two most outer joists? or is it doubling up (laminated) on the last joist? 
RS

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## METRIX

Metrix, couple of questions
1) when you say blow out the timber, i presume this is from nailing into the end grain? 
35mm timber tends to blow chunks off it when skew nailing with the guns the extra 10mm makes a big difference when framing stuff up, 35mm is on the border of being to thin to handle the gun nails. 
2) for the perimeter beam to pickup all the joists, what does that exactly mean? 
Run a continuous beam all the way along the ends of the joists, it's a lot quicker than blocking out between each joist 
3) when you say "or block these out", i presume this is just adding extra blocking to the two most outer joists? or is it doubling up (laminated) on the last joist? 
Run a row of blocking along the end of the joists which are not attached to a ledger or similar, usually you block out every 2nd joist. 
Don;t bother laminating bearers when you double them up, because you cant hold them onto the post securely, unless your going to sit them on top of the post, and strap them, which is a bit gumby but works.
They need to sit either side of the post which will be notched on both sides.

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## Rompastompa

Thanks Metrix, 
I think this may have strayed from my design a little, but I could be wrong. 
As my joists/bearers are on the same level I wont have any open ended joists, I presume you mean hanging over like the below picture?   
I think I understand what you mean by joists rolling over now, if the joists are on top of the bearers they have no sideways support as they are only secured to the bearer at the lowest point, causing a pivot point effect under load on deeper joists? 
As mentioned, mine will be on the same level, all joists will be secured to the bearers directly via the appropriate joist hangers, which will be screwed in... i know, i know, most use nails, but I'm a drill man... 
So based on the above, do I still need blocking? I was thinking now to add two blocks between the outer two most joists to add strength to the 250/300 bearer overhang, but the joist hangers should keep the boards from wanting to roll shouldn't they? I will be using angle brackets for the perimeter joins of the deck to provide extra strength, or should joist hangers be sufficient with the blocking between the last two joists? 
if I've misunderstood, let me know, thats why I'm here...  :Read:  
RS

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## METRIX

OK, if your going for a deep joist system with hangers, then yes, this will stop the joists from rolling over. 
I would still put blocking through the middle of the joists if you are  doing one continuous joist of 3m with intermediate bearers sitting under  the joists, and end bearers level to the joists. 
If you are going  for intermediate and end bearers level to the joists then blocking of the joists would not be required for your span, but this would be  an in efficient way of building it, unless you have height restrictions. 
I don;t understand your overhang if your going for deep joists, then the end bearer is the end point for the deck, you cant overhang past this point. 
Angle brackets are fine for the corners, Bunnings actually have a good quality Galvanised bracket which will suit 140 joists perfectly, they are cheap, Dunnings branded. 
Also if your doing double end bearers and joist hangers, that's sort of pointless, if this is the case then you will need to bolt the bearers together and have no space in between them as I explained earlier, you would need the double end bearer to act as one, but then you get the problem of attaching the double end bearer to the post securely without sacrificing the strength of the post too much.

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## Rompastompa

Thanks Metrix, 
Correct, I am going bearers/joists on the same level due to height restrictions and keep everything as low as possible. 
Below is a rough outline of what goes where, please note this doesn't reflect the actual plan of number of joists, etc for my project as I have drawn it smaller to give you an idea. 
The overhang on the bearer is shown at the bottom, where the bearer hangs over/cantilevers from the last stirrup/post support. This is where I have added the blocks to help strengthen the edge. overhang should only be about 200mm based on plans. 
All stirrups (metal legs) will be secured by 2 bolts, the brackets at the end corners will be secured with 3 bolts each on the bearer, and joist. 
All bearers will be laminated together, no spacing and I believe wont need to be notched as they will be bolted directly to the metal stirrup post supports.   
Also, When you say 
"Also if your doing double end bearers and joist hangers, that's sort of  pointless, if this is the case then you will need to bolt the bearers  together and have no space in between them as I explained earlier, you  would need the double end bearer to act as one, but then you get the  problem of attaching the double end bearer to the post securely without  sacrificing the strength of the post too much." 
Thats correct I will be laminating the bearers together with no gap, but this won't provide any issues with the post support as I'm using the metal pryda stirrups that bolt to the bearers? 
RS

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## Rompastompa

Hi Metrix, 
Further to the above, I am now intrigued with floor loading as you mentioned 62kg/m2, I have found a piece of software that supposedly provides some detail around this. 
Are you able to shed some light on this and see if my figures below are somewhat accurate? 
Bearers - 2/140x35 continuous span of 1520mm centres, 1600mm spacing show them running at 44% capacity at 62kg/m2 1.5kPa, 1.8kN
Joists - 140x35 single span of 1580mm, joist spacing of 425mm centres show them running at 66% capacity at 62kg/m2 1.5kPa, 1.8kN 
Based on this, am I able to work out deflection? 
Used 62kg/m2 as this is what you mentioned before. 
Do these figures sound right? wrong? off? or what not? 
Appreciate your help with the understanding. 
RS

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## METRIX

OK, your picture makes sense now, The overhang is fine, don't worry about brackets in the corners, use joist hangers and straighten the outside edge, nail this side into the ends of the bearers. 
If your going for stirrups, then laminate the bearers with nails, sit them in 90mm U stirrups and pack them out, then bolt them in, then put a few bolts along the top of the bearer, it won't go anywhere.
In regards to your figures, For the design you have come up with. 
 2 x 140x35 bearer with 1520 centers at 62kg will be loaded to 25% with 1mm deflection, you can actually get away with a single 140x35 as the end bearers, this is rated to 57% with 1mm, still need double for the intermediate ones.
Joists 140x35 span 1580 are loaded to 60% with 2mm deflection,  
I would have chosen to use 190x45 as the end bearers, and spanned them  2280, this gives you 88% loading with 2mm deflection, and used a single  190x45 as the intermediate this would give you 64% with 1mm deflection.
I would have also have gone for joists of 140x45 which gives you 48% with 1mm deflection, the extra 10mm makes a lot of difference. 
Again, personally I would prefer to see 45mm as bearers

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## Rompastompa

Thanks Metrix, 
Was back at the supplier today for other needs and got talking and they kindly offered to swap it out for the bigger size, for the extra cost of course, so now I'm back to 140x45 and feeling better. 
Can't go 190 due to the low height restrictions. 
RS

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## METRIX

Should have worked out cheaper to exchange 4x 35mm and replace with 2x 45mm for the perimeter bearers.

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## Rompastompa

Thanks Metrix, 
thought about doing that and replacing only a certain number with 45s but wanted the deck to feel more solid especially given that the wife Is now calling it the dance floor  :Smilie:  and plus it makes it easier to picture frame the deck at the end of the day. 
RS

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## r3nov8or

So you'll be dancing to old 45s on new 45s  :Smilie:

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## METRIX

> t the wife Is now calling it the dance floor  and plus it makes it easier to picture frame the deck at the end of the day. 
> RS

  Exactly right, this is why I always rate my decks at the higher end, because they are used as gathering points at parties, and yes they are also used as dancing platforms quite often. 
This translates into engineering them to cope with more live load than say in a dining room. 
What timber are you putting down for the boards, I hope it's not pine  :Eek:  ?

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## sol381

what,, you mean those pros on backyard blitz and better homes and garden are doing it wrong by using pine.

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## METRIX

Nah, pine has it's place, so do nails, they are usually tied together, I don't think you would waste money screwing a pine deck down   :Smilie: . 
Any decks I do , will always be preference to hardwood and screws, but there is still a segment of the market that want's pine and nails  :Mad:

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## Rompastompa

Looking at the ekodeck boards with hidden fasteners, like the idea of a semi maintenance free deck.

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## METRIX

Nice, I have done a few of these, the new system with hidden fasteners is the way to go, using the original system with the CAMO fasteners is a pain, it splits the edges of the board and top screwing is no good, you can easily mushroom the product if the screw is over-driven even slightly. 
You definitely need to build it strong as this is a HEAVY product, the wide boards look better IMO.

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## Rompastompa

Thanks metrix, 
Does going back to 140x45s make this a strong frame for that deck? 
ill have a look at the wider boards too as I was originally looking at the 88. 
RS

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## sol381

> So you'll be dancing to old 45s on new 45s

    B 
No-one else responded so here goes... :brava:

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## Rompastompa

Just rang and checked on the 137s and Bunnings didn't have much in stock, and due to the deck being low, maybe I would be better off
with the 88s on the new 45s  :Shock:  whilst dancing the old 45s to aid ventilation through the deck boards.

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## METRIX

Just go to another Bunnings for whatever you are after, these have to be delivered anyway so it makes no difference, these are very difficult to transport on your own as they are very floppy, you cant put them on your roof. 
The 35mm setup you had was fine, bear in mind EKO requires 300mm clearance under it for proper ventilation, actually you should have this for any deck.
Also there are a few limitations to EKO that timber doesn't have such as expansion gaps etc, check out their installation requirements. 
I try to make any EKO decks 5.4m long or wide, as this is the set length the boards come in, this way you need no expansion joins and there is zero waste (this is important as the product is $$$$). 
EKO boards are required to span across 4 joists minimum.

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## Rompastompa

Hi Metrix, should just be okay with the 300mm clearance excavation beneath the deck, but it might be a little less in areas maybe around 200mm? especially around the outsides as I am tapering the underneath of the deck to drain into an existing drain. 
However, my concern now is to do with ventilation, the area of the deck will be surrounded by concrete on one side, another two will have fences and the front will be about 75mm above the existing grass level but because of the 140mm deep joists it wont allow for any airflow to actually get underneath the deck, the only gaps would be the 6mm in the boards, and a 25mm or so gap between the fences. 
Should I just count my ducks and walkway? or is there a way?  :Frown:  Dont want to go to all this effort and have the deck only last a few years. I would ensure that the drainage is 100% before laying anything. 
RS

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