Free standing deck

[Lappa]

I want to build a free standing deck over a paved area. It will be a box frame consisting of 150 X 50mm timber. I have attached a drawing. What I need to know is how many footings do I need to support the frame. They will be adjustable units placed on the pavers, not dug into the ground. Looking at span tables I think I need 5 on each 6.5m outer bearer but I would probably have 5 in the centre as well to stop bounce.
Any info would be appreciated.

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[rwbuild]

Perfect. How high off the ground will it be?

[Lappa]

Thanks Ray.

The bottom of the bearers/joists will be 100mm off the ground if I use 150mm bearers/joists. I only have 269 mm from the pavers to the door sills so take off 19mm for the top decking boards and 150mm for the bearers/joists and I'm left with 100mm.
Looking at my options for fitment, decking boards etc I may be better going with diagram 2 in this new upload. This means the decking timber will run across rather than along the length. I will need a row of footings across the centre (5) plus 5 down each side. Maybe another in the middle at each end? See diagram 2

499409

[Wrongwayfirst]

Max joist spacing for me on a 19mm board is 450mm and I would be looking at four rows of footings (1166mm spacing on 3500mm width)

I see you have changed orientation, for my liking I run the boards across the viewing angle so you look across the boards not down the gaps this way if your lines are not completely straight you don’t see it.

I am not a builder and bow down to those with more knowledge :U

cheers
wrongwayfirst

[aldav]

Do you already have the timber Lappa? If not you may be better to go to a more conventional design using 100x50 hardwood bearers and 90x45 MGP10 joists. This would give you a framing height of 190mm max. so still within your height allowance of 250mm. I'm guessing your plan with the 150x50 would be in hardwood and you will be using joist hangers? I don't have access to any tables of timber span requirements for this type of construction, although you may be able to find something on the net, I suppose you've already looked.

[Lappa]

I haven’t bought anything yet - just in the planning stage. I was going to use 150x50 LVL timber. The hardwood at the moment is like a corkscrew and no one will guarantee it being straight. The reason I ask re the footings is span tables confuse me with one set for bearers and one for joists, Floor Load Width etc. so I thought I’d ask the experts.
I forget about the 450 centres for 19mm - thanks for that wrongwayfirst so I’ll redraw. The span table I have says 150x50 single span is 3.35m (2 footing) and 4.14m continuous ( if I read it right - 3 footings). So if I go to the first diagram, across the 3.5m, I see 3 footings required but I’m not sure how many down the 6.5 m length.
The reason for running the boards out from the wall rather than along the wall is for two reasons. This is an old house and all the veranda boards run that way and it’s easier to compensate for irregularities along the perimeters.
I don’t mind having too many footings; I’d rather a stiff floor than a springy one and it’s going to have a very heavy hardwood outdoor table on it.
I’ll post a new drawing with 450 centres and where I think the footings will go for perusal and comment.

thanks fellas

[riverbuilder]

If you can find ANY lvl materials at the moment, let me know please, we’ve been waiting for months for a couple of orders, still no sign of them.
a better option is old school 90x70 treated pine bearer and 90x45 treated pine joists, never touch it sgain as long as you use galvanized or stainless fasteners for everything.

[Lappa]

Thanks. What’s the span between footings for the 90x70 bearer? My span table only shows 2/90x45 for bearers. Might need to visit the chippies at work��

[riverbuilder]

Thanks. What’s the span between footings for the 90x70 bearer? My span table only shows 2/90x45 for bearers. Might need to visit the chippies at work��
I’ve always known it to be 1800, but that was for hardwood I think, I would think dividing the run into equal spans around 1500 should see you straight though, unless you’re planning on having weight watchers club meetings on the deck with all the members from the western suburbs of Sydney attending.

[aldav]

The tables I've got show 2/90x35 seasoned softwood F7 as not suitable for floor widths over 1200mm. Even at 1200 floor width the spacing of the supports is shown as 1300mm.

[aldav]

If you do want to go the softwood bearer route MGP12 has just over 20% more bearing capacity than F7. That should allow you to have 5 runs of 2/90x35 MGP12 bearers (1625mm centres on the deck length and supported at 4 points) and 9 runs of MGP10 joists at (roughly) 450mm centres.

[Beardy]

Another option to consider that I have done is use galv steel RHS joists and Wurth self drilling screws. Much better span capabilities and more cost effective not to mention the availability issues with timber at the moment.

[Lappa]

Another option to consider that I have done is use galv steel RHS joists and Wurth self drilling screws. Much better span capabilities and more cost effective not to mention the availability issues with timber at the moment.

Thanks Beardy.
I’d already been looking at Boxspan early in the piece which is where the 150x50 dimension originally came from but their adjustable footings needed a minimum of 220mm beneath the bearer. While continuing the search for adjustable footings of the size I required, another company selling steel sections said it had to be a minimum of 400mm from the ground for warranty etc.
This is why I stated looking at LVL timber and using 150x45 ( closest to 150x50 that I had span tables from for the Boxspan)
Still haven’t ruled out steel but haven’t got prices yet.

[Lappa]

Had a great chat with Ray (RWBUILD) yesterday and he kindly ran the 150x45 through his program and came up with a plan with dimensions and footing spacing.
great help - thanks again Ray:2tsup:

David (Aldav) had also been beavering away drawing up a plan using maybe more readily available 90x45 - once again, great help - thanks again Dave :2tsup:

Thanks to all who replied - gotta luv this forum!

[Beardy]

Thanks Beardy.
I’d already been looking at Boxspan early in the piece which is where the 150x50 dimension originally came from but their adjustable footings needed a minimum of 220mm beneath the bearer. While continuing the search for adjustable footings of the size I required, another company selling steel sections said it had to be a minimum of 400mm from the ground for warranty etc.
This is why I stated looking at LVL timber and using 150x45 ( closest to 150x50 that I had span tables from for the Boxspan)
Still haven’t ruled out steel but haven’t got prices yet.

I didn’t bother with boxspan, I just used Onesteel Duragal RHS, there are span tables on their website. Likewise I didn’t use their adjustable footing system , I just cut gal posts and concreted then in and fixed then to the framing. I used 150x50 and are set 50mm off the ground so that it is just one step high

[Lappa]

Thanks Beardy.
Mine is going onto a paved area so I don’t want to dig in footings hence the adjustable footings.
Rough retail costs of 150 x 45 H3 LVL timber itself (without hangers, adjustable feet etc etc) is around $1800. Boxspan steel is about $150 dearer.
I’ll check Onesteel Duragal - thanks for the link.

Just checked Onesteel Duragal 150x50 x 2.0mm - works out about $2780.

[apple8]

Just to satisfy my curiosity, if the footings are not dug in and sitting on pavers how is the deck anchored down?

[Lappa]

By the weight of my outdoor table:D

its freestanding so it does it need to be tied down?

499542499543

There brick wall on three sides I could fasten it to if that’s required.

[apple8]

Table was what I was thinking too. While the weight may hold its position relative to house, one of the thoughts running around in my somewhat empty head, with a deck out in the weather, timber movement/warping or slight soil movement you could end up with some footings losing contact with the ground and subsequent bounce.

[apple8]

Just a thought, I know you don’t want to dig your footings in, but maybe screw-in footings (https://housetradesupplies.com.au/otter-ground-screws/3445-otter-screw-in-ground-screw-stirrup-690mm-gsug0690-9311496036840.html) could be helpful as you would only need to lift a paver to install. I believe they are available from a big green shed.

[Lappa]

Table was what I was thinking too. While the weight may hold its position relative to house, one of the thoughts running around in my somewhat empty head, with a deck out in the weather, timber movement/warping or slight soil movement you could end up with some footings losing contact with the ground and subsequent bounce.

I’m using screw adjustable bearer supports, mainly because I can’t guarantee the pavers are all exactly at the same height. Any movement (shouldn’t be as the pavers have been down for 35 years) can be adjusted out later.

[Lappa]

I’m a timber guy but SWMBO wants me to look at composite boards so we don’t have to re-coat them yearly like you do with timber decking.
I would be interested to hear from those who actually have it or have installed it as to your opinion. Most samples I have are 23mm thick so I have to decide before building the frame. Longevity, wear/scratches, slipperiness, installation, etc
Also opinions on the the solid vs the capped types.
Thanks

[rwbuild]

If it is going to get summer sun for any length of time ( faces north?) it will expand and contract a fair bit, also how do you like your feet done, rare, medium rare or well done, nigh impossible to walk on in bare feet in summer. UV has a long term affect on it too despite what the manufacturer states and the colours fade fairly quickly.
In summer they sag between the joists (3mm to 5mm), winter very minimal.
Easy to keep clean, mild detergent and soft broom then hose off.
All the above is based on my observations of it and personally, I wouldn't use it.

[aldav]

If you're going to use composite decking and you want to run it along the 6.5 metre length you'd need a control joint in the middle due to its propensity to 'grow' in length. Like Ray I'm not a big fan. :no:

[Wrongwayfirst]

If it is going to get summer sun for any length of time ( faces north?) it will expand and contract a fair bit, also how do you like your feet done, rare, medium rare or well done, nigh impossible to walk on in bare feet in summer. UV has a long term affect on it too despite what the manufacturer states and the colours fade fairly quickly.
In summer they sag between the joists (3mm to 5mm), winter very minimal.
Easy to keep clean, mild detergent and soft broom then hose off.
All the above is based on my observations of it and personally, I wouldn't use it.

+1 what he says, neighbor has 10mtr run and it grows as the sun comes up and shrinks as the sun goes down

[Lappa]

Thanks all.
Mine faces east and is under a pergola roofed with tinted SunTuff which goes out 1.5m past where the edge of the deck will be.
It may get direct early sun in summer on the front of it but only for a very short time. If I run it the way I am thinking, the longest run will be 3.5m. If I run it the other way (6.3m) it will have to have a divide in the centre as the longest length in most is 5.4m.
Must admit, I’m not a fan but I need to look at options.

[riverbuilder]

Don’t use composite boards, theyre crap.
absorb heat like a sponge takes water, they buckle incredibly, and they are extremely slippery. The only thing I would ever recommend or use them for is vertical screening. Merbau or spotted gum, the maintenance is nothing.

[Lappa]

Which is better or are they much of a muchness. Blackbutt or Spotted Gum?

[riverbuilder]

Spotted gum by a mile

[Lappa]

I was speaking to a relative in Melbourne whose husband is a developer/builder. He mentioned that he has used aluminium subframe for decks and it was easy to assemble, strong and light.

ClickDeck Framing Products (https://www.clickdeck.com.au/products)n

it’s about $400 dearer than building with 190x45 H3 timber (including screws, hangers, freight etc), but price includes all fittings etc and includes adjustable posts which hasn’t been taken into account re the timber built price so the price difference becomes closer.
Has anyone used aluminium or has thoughts re it’s use?

[Lappa]

Don’t believe what companies post on their sites.:no:
I got an actual quote for an aluminium frame, drawn up by them and with freight, it’s about $1400 dearer than timber:oo:


Another question for those who build decks or have built decks.
136 x 19 or 85x19 spotted gum.?
A few searches show that 136x19 timber (spotted gum, Merbau, blackbutt) is prone to cupping and I can’t afford 136x32 as suggested.
So, should I just go with 85x19?
BTW, whatever I use will have two coats bottom side before fixing.

[riverbuilder]

Go with the 4”, the cost differential is massive. The 6” does cup a bit in exposed areas.

[Lappa]

Before

501115501116

After

501118501119

and no, I didn’t do it. Too many screws for me :oo: