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Hi,
I am planning some decking and a pergola, I would like to know if I am required any planning or building permits for the following:
1: extend my decking area from my alfresco (which is situated on a slab) and extending outwards in 3 directions, adding approx. 18sqm to the current decking area, the new decking will require footings of course, and be attached to the existing bearers on the alfresco. so I was wondering how deep footings should be ideally, post holes will be 1117mm on centre along the length, and 900mm on centre on either side.
decking will be 7200mm long and 4500mm wide, with a 380mm wrap around on one side.
currently the decking perimeter is the two brick piers, see below for my plans.
2: also planning an open "Hampton style" pergola that will cover the 18sqm decking, which will be attaching to the alfresco (approx. 2300mm above planned decking) so much stronger footings required (see the above pictures, the 4 deeper footings which are offset from the deck footings will be supporting the pergola, I'm not sure on minimum required depth but I will probably attach the posts to stirrups which will be secured in the footings.
3:A second smaller decking approx. 2.8 sqm in size from the laundry exit which will be anchored from the brick wall and require some footings, however i'm unsure as to the minimum depth for footings.
I called Casey council who recommended talking to a surveyor, but am I better to talk to a builder? and I am unsure about having plans made up professionally, at least for the decking and pergola and I haven't worked out how much materials will cost yet but if I am able to build everything myself I would like to save on costs where I can.
thanks heaps
Welcome to the Bunnings Workshop community @TimGeo. It's a pleasure to have you join us, and many thanks for your questions on building a deck.
Ultimately, it will be up to your council whether a permit is required to build your deck. It sounds like they are deferring their response until you present engineering diagrams to illustrate the extent of the works. An engineer specialises in construction plans and will be needed if you are incorporating a pergola. Soil tests will be needed to determine the size of footing required in your area, and the council should either be able to supply these or direct you to a surveyor that can conduct them.
There is no one size fits all depth for footings. It comes down to the specific type of soil in your area. An engineer will take the results from the surveyor and cross-reference them with tables to determine the size and depth of the footers. If you're willing to put in the time and educate yourself, this is all work you can do yourself if the council can provide soil tests from your area, but it starts to become quite complicated.
Please let me know if you have any questions.
Mitchell
A soil surveyor is the first place to start when determining the size of footers required for your project.
Keep us updated, and reach out if you have further questions.
Mitchell
Hi @TimGeo,
Changing to a free-standing structure could potentially help avoid certain permits. However, that would be very location-specific and dependent on your local regulations. Your local council building advisor is the best contact for such information.
Mitchell
Hi, I've been mulling over this more than I should be but I have a design I would like to run by you guys to see if this is structurally sound. I know it's only a small area but I don't like to take shortcuts and a little bit of a perfectionist. I don't do many building projects so I am not familiar with the integrity of certain applications.
anyway, I have a deck I have designed for my laundry area and when I complete my paving the deck F.F.L will be 180mm so I have opted to build bearers and joists in one layer.
I had initially designed it with 6 concrete supports however I would like to save some of the cost by recuding it to 4 concrete supports and cantilevering the deck by 250mm on each side and the farthest edge away from the house.
The issue I've got is that I don't know if the design is rigid enough and not cause any flex.
The first image is the completed design, below is my garden bed consisting of sleepers so I will be scribing the last board to that profile
Total decking space is 2112mm x 1205mm
With the decking being a freestanding deck, here is my intended deign for bearers and joists, with the bearers consisting of 2x(90x45)
The posts are 600mm O/C front to back, and 1500mm O/C left to right.
What I didn't show here are noggings which I will definately add for extra strength but I wanted to get an idea of any issues with this design (if there are any) and aside from joist hangers what other hardware will I need for this?
Hi @TimGeo,
Unfortunately, that design won't work for several reasons. 90 x 45mm isn't capable of spanning those distances. It's already a very small calibre of timber for use when constructing a deck and needs to be supported at least every 1000mm. You also need a post on the front where it's hard against the garden bed. You might intend on connecting it to the garden bed for support. However, now you have a single 90 x 45mm between the posts and a second counter levered off it. In the middle, you have a joist spanned over/near 1000mm that joins it perpendicularly. The whole weight of the middle portion of the deck is being transferred onto the one joist running between the posts. You could get away with this design if you bumper the timber up to 140 x 45mm or installed additional posts. At a minimum, you need support as marked below with the star. Also, you can't have a counter lever joined onto the deck. The timber frame needs to span the whole length, similar to the wall side. I've marked a red line where the timber needs to span the entire length.
Apart from joist hangers, you'll need some bugle screws to make the timber joints in locations where joist hangers won't fit. Like the two parallel lengths of timber joined together in front of the garden wall.
That might be unclear, but please let me know if you have questions.
Mitchell
Just to clarify @TimGeo, you'll likely be able to stay with 90 x 45mm if you return to the six-post design. Have a play and share what you come up with and I'll see if I can make some final edits to your design.
Mitchell
