All Hands On Deck

[2 Bob]

G,Day All,
I Hope some one can help me,I am building a Deck which will be 150mm off the Ground the stumps will be buried 300mm in Quick dry cement. the beams will be treated pine [ I know, they will be short stumps]I will be using 90mm Merbau The width of the deck is 4.1x6.1 long. my Question is do the beams Have to be spread at 450 intervals is there a required measurement and at 4.1x6.1 How many stumps would have to go in?Any help and advice is really appreciated.

Cheers to all 2 Bob

[ausdesign]

Greetings 2 Bob.
A couple of points - I assume your in the sandy soil around Hastings which if the case will be rated as Class "A" or "S". The minimum post embedment will be 400mm.

19mm merbau can span up to 500mm

The pad size is related to the area of deck supported. ie a 250*250 pad with 150mm of concrete under the stump can support 5m2 of deck area. A 350*350*200 thick pad can support 10m2

With a minimum height of 90mm each for your bearers & joists the deck will be 200mm above ground level even with the bearer sitting in the dirt.

The stump spacings are tied in with the sizes of your bearers & joists (or visa versa ) 90*70 f5 treated pine bearers with a spacing of 1200mm can span 1400mm and 90*35 joists at 500 spacing can span 1500mm.

[2 Bob]

Greetings 2 Bob.
A couple of points - I assume your in the sandy soil around Hastings which if the case will be rated as Class "A" or "S". The minimum post embedment will be 400mm.

19mm merbau can span up to 500mm

The pad size is related to the area of deck supported. ie a 250*250 pad with 150mm of concrete under the stump can support 5m2 of deck area. A 350*350*200 thick pad can support 10m2

With a minimum height of 90mm each for your bearers & joists the deck will be 200mm above ground level even with the bearer sitting in the dirt.

The stump spacings are tied in with the sizes of your bearers & joists (or visa versa ) 90*70 f5 treated pine bearers with a spacing of 1200mm can span 1400mm and 90*35 joists at 500 spacing can span 1500mm.

Thanks for the reply,My thinking is to coach screw the bearers to the post and the merbau straight on top of the bearers,I have to be honest I am not sure of the term Pad, ?is that what goes under the post to give it firm ground to sit on? or is that Instead of using post laying the bearers straight on top of The pads<which I am assuming are made out of Concrete.:confused: I cant go any Higher than 150mm as thats the hight of the step.I was planning to have the post above ground by 40mm Add 90mm for the bearer and 19mm merbau which gives me near 150, the soil isnt sandy so what spacing would be recomended for a 6.1x4.1 deck,and is it possible to use concrete pads instead of post:confused: .any way thanks for reading and the reply all advice is Greatly appreciated.
Cheers,2 Bob

[ausdesign]

My apologies for the slow reply 2 Bob.

If the merbau decking is going across the 6.1 then you will need 13 posts & 13 bearers ( 6100 divided by 500 ) and 3 posts along each (90*45 f5 treated pine)bearer. A total of 39 posts.

Yes the 'pad' is the concrete under the post to give the required bearing area (pressure) on the soil. With so many posts you will require the minimum pad size of 250*250*150 thick. On clayey soil the required depth is 500mm.

Yes you can do away with the posts but the concrete will need to be the above dimensions and the bearer would need to be fixed down with a bracket of some sort. If the bearer is in contact with the ground it will need to be 'H5' treated.
In both situations I would recommend H5 in any case for durability.