12.7 x 5.1 New Deck - Some Advice Please

[oohsam]

Hey Guys,
I have been doing research for the last 9 months on this deck that I would like to build in my home.
The deck is quite large but it is very low to the ground (about 200=300mm). We are going for a 90x90 Treated pine stump layout, and the bearer on the left hand side will be dynabolted to the brickwork. (See Picture)

Stumps will be 1500 apart, and becuase the deck is so low to the ground, we will be bolting the bearers to the side of the stumps (as i cannot afford to put them ontop of the stumps due to height restricions).

I will then use joist hangers between the bearers to place the joists.

Is there a problem with it doing it this way, basically the top of the stump, the joist and bearer will all be the same height, so basically the weight will be reliant on the bolts and joist hangers...??

If anyone has advice on this please comment, as I am still a novoice but am open to suggestions..

I have addeda picture of my house and where the deck will go.

[brynk]

gday.

it is no problem to use engineered joist hangers. (one of the) products you want is made by a mob called pryda
http://www.pryda.com.au/catalog.php?sectionid=20&type=Hangers%20and%20Truss%20Boots

on a side note, which direction are your decking boards going? & what size timber are you using for your bearers & joists?
you might be able to cut down on the number of posts required if you take advantage of a cantilever at either end of your bearers.

[oohsam]

Brynk,
Yes, I will be using this type of joist hanger

http://www.pryda.com.au/catalog/connectors/images_th/FB50180.gif

[Bruce Cole]

I just had a deck installed which was slightly bigger (4.5 x 15) than the one you are planning. It too was only 150 - 300 off the ground.

I found that by using a galvanised steel frame which sits on the ground it was cheaper and easier to install than wooden one, plus it will not rot.

[oohsam]

Galvanised frame would be good, however my land is not level. I am on a slope and the land drops quite a bit towards the fence line, so stumps are really my only option.

[oohsam]

gday.

it is no problem to use engineered joist hangers. (one of the) products you want is made by a mob called pryda
http://www.pryda.com.au/catalog.php?sectionid=20&type=Hangers%20and%20Truss%20Boots

on a side note, which direction are your decking boards going? & what size timber are you using for your bearers & joists?
you might be able to cut down on the number of posts required if you take advantage of a cantilever at either end of your bearers.

Gday Brynk
I will be using the Pryda joist hangers (second image on the link you sent me)
The deck boards will be running paralell with the house (so looking at my picture, they will be running vertically).

So the bearers will runn vertically and the joists horizontally. Which leaves me with only one option to cantilever the bearers, which will be at the top end of my picture.
I dont think that will work as the space between the last stump and the fenceline will be 740mm (stumps are 1500 apart).

Is this ok to not have supporting stumps ?
Is there another way I can do this?

Cheers.

[SilentButDeadly]

OohSam,

I have a couple of observations that might help with your height issues and simplify construction.

Put your bearers and joists in the same plane all sitting ON the stumps (unless your stumps are steel). Use something like 200x50x2 galvanised RHS steel for both (may also be able to use 200x50 C section purlin which'd be cheaper may be more fiddly). If you do use the RHS then you'll probably only need two bearers - one at mid deck 2.6m & one at the outside 5.1m. Stump centres could then be increased to 2100mm and reduced in number - all depends on the span tables. Joists go in between at chosen centre (600mm?) and are fitted either end with those Pryda joist hangers (make sure you use Flashtec tape in between ahnger and steel to ensure weather proof no rust connection). All steel can be cut to size by your supplier off site...so all you have to do is screw it all together.

You could come down to 150x50x2 RHS but you may find you need extra bearer (more joist hangers, more fiddly) and reduced stump centres (so more stumps) ...

[brynk]

gday oohsam

you could certainly increase the depth of your bearers & this will reduce the number of posts required and going steel is also a viable option that might be competetive to your bearers' & posts' cost - the goal is to span as far as you can with steel to make it economical by reducing drastically the number of holes you need to dig

if you are getting approval (you are, aren't you? :U) then you will need to have engineered the steel bearers & this will add cost unless you can use some already-engineered system from one of the manufacturers that can be used in conjunction with AS1684 (the residential timber framing code). i don't know of any but i'm sure they exist

some considerations - if you use R(ectangular) H(ollow) S(ection) you would need to lay it such that deep points down, and you will need a minimum contact area for the joist hangers to fix to properly to achieve their rated strength. alternatively you could use a hot-rolled I beam (& C-channels on the outsides) & rest your joists on the bottom flange. to avoid using 3 bearers you must go to 240x45 F7 treated pine joist which will allow you to span 5000(+/- 30 :wink:) but might be cutting it fine for your depth requirements - that aside you need to work out how much a post will cost you to do as you will need 7 posts / bearer ( according to my copy of 1684 which is slightly out of date) if you use the following arrangement...

2x 170x35 seasoned treated pine for the 3 bearers (one left & right & one straight down the guts) from the house to the fence thusly:
house -> 500 cantilever -> post -> 1900 -> post -> 1900 -> post -> 1900 -> post -> 1900 -> post -> 1900 -> post -> 1900 -> post -> 500 cantilever -> fence
(breathe)

let your decking hang an inch or so over the ends of the last joists to close the gaps between the fence & the house
you can also use 170x35 seasoned treated pine at 600 centres for the joists which will span the (2550 - 35 - 70 - 35 =) 2410, but you can only span 500 between joists with the hardwood decking so they will need to go in at 500 centres

r's brynk

[oohsam]

Geez Brynk, You really know your stuff. You have given some great advice. We have decided to stick with treated pine stumps and do it the old fashioned way...LoL...however, we will steal your cantilever Idea...keep reading for more detail..

I was out there today, clearing the area (had all weeds and junk there that has accumulated over the last year) now i can actually see the ground!

My mates dad came by, and he's built a few hundred decks in his time.
He said we would have enough room to bolt the bearers to the side of the stumps but then have the joists sit ontop of the beaerers, so we wouldn't need joist hangers, which is a relief.

We will however need to use treated pine bearers as there will not be much clearance between the ground and the bearers so that is just a safe guard to prevent rot etc.
We have decided to use cantilever all around, with this formation:

From house to Fenceline:

House -> 509 Cantilever -> 1360 -> Stump1-> 1360 -> Stump2-> 1360 ->Stump3->509 Cantilever -> Fence

And in the other direction

House -> 520 Cantilever ->Stump 1 ->1300 -> Stump 2 ->1300 ->Stump 3->1300 ->Stump 4->1300 ->Stump 5->1300 ->Stump 6->1300 ->Stump 7->1300 ->Stump 8>1300 ->Stump 9->520 Cantilever -> Fence

So there will be 3 Rows of bearers and the joists will go ontop at 4500 spaces.

My mates dad will be supervising the whole thing, basically telling me and a mate what to do and guiding us in the right direction. I know the stumps are closer together than what is normally expected (1500) but we wanted a nice and sturdy deck with no bouncing that could support alot of weight, as we will be entertaining alot on it and could have quite a few people on there, as its quite a large area...

I'll be out there tomorrow marking it all up with stringline and marking the holes where the post holes will go so we can get a good visual..Will post pics up..

If you have any advice for me please dont hold back : )

Cheers

[digg]

why not use stirrups bolted to bearers 900mm long encapsulated in concrete this way you can use blocks to get heights and levels perfect ,then dig holes place stirrups and concrete ,as long as you use pryda termite stirrups and 75mm off dirt

[oohsam]

I considered the use of stirrups....However Im just not convinced I want to use them.
The cost of stirrups vs stumps is about the same so there is no real advantage to me in using them, other than a little bit of extra labour...