2/90 x 45 or 90 x 70 for 6865 x 6000 deck

2/90x45 means what you thought . you can either nail them side by side, or bolt then either side of your stumps (with a notch in the stump for them to rest on.

you can use 90x90, but the program I have for spans, has 2/90x45 slightly stronger than 90x90.

If you have a look at the stickies at the top of teh "Decking" forum there is a great decking calculator, just plug in your dimensions and it works out what you need.

There are also several span tables. the last one is a very simple one I made up using F5 and common sizes.

What program did you download?

Originally Posted by bpj1968

you can use 90x90, but the program I have for spans, has 2/90x45 slightly stronger than 90x90.

Yeah, this fact interested me when I started out, and is because the two different timbers will have unique grain patterns and when combined adds some extra strength. 1 + 1 > 2

Also, maybe not for 90x90, but dimensions like 190x90 are almost impossible to find, and so 2/190x45 is the solution.

Hi,
The program i downloaded is called timber solutions

I will have a go at the one in the 'sticky' post now

thanks heaps

I think i,ve finally got my hea around it.

The only thing that doesn't make heaps of sense to me is why the FLW for bearers on all the different charts i have looked at jump from 1200mm to 2400mm without the 1800mm option?

I'm assuming i can check both the 1200 and the 2400 option and divide it by 2 for the 1800 that i want seeing as 1800 is in between 1200 and 2400

Does that question make sense?

I use Timber Solutions all the time, just the way you described it sounded like something else.

What you propose about 1800 FLW sounds good, BUT WRONG.
eg 2/290*45
1200=4450
1800=3640
2400=3150.

You can generate your own charts using Timber Solutions.
The span table I made and posted has odd FLW's which relate to specific size joists.

I hated planning joists that could span say 1500 yet the span table had bearers with FLW of 1200.
Although it does pay to go a bit closer for stability rather than the absolute maximum

Ok Brian,

Sounds like i'm almost there.

I'll be a bit more direct with my question (sorry to be a pain)

My timber solutions table states the following for 2/120x45 for bearers (continuous span):
FLW 1200 = 1800 span
FLW 2400 = 1300 span

Therefore, If I want FLW 1800, my span needs to be 1550 (half way between 1800 and 1300 just as my 1800FLW is half way between 1200FLW and 2400FLW)

Have i got it or I'm way off??

I understood your question, obviously my answer was unclear, but it is not simply a matter of basic maths

In Timber solutions you can do it to your own specs.
"Geometry set" option in Timber solutions.

1st line 1000 = Min span to list
7200 = Max span to list
100 = Increments to show span i.e. round down to nearest 100

2nd line
FLW of 1200 2400 4800



These can be changed


1st line rounds down to nearest 10mm (although going to the absolute max not an idea structurally)
FLW in the table will now be 600, 1500 and 1980

You can enter specific dimensions you are after (1500) hope that explains it

Gotchya brian!
Thank you so much.

Just found out that the 140x45's i'm getting from bunnings are mgp10 which is cool as it has a capabilities for greater FLW's and spans!

Will post up a pic over the weekend of the where the deck will be going
(I've just finished digging out the dirt)

One more thing only use Galv or stainless, nails,bolts etc with Treated pine. Zinc will not last