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Low Merbau Deck on Apartment Balcony

Hi,

I'm planning a very small section of deck on my apartment balcony. The total area I've allocated for the deck is 2680mm x 1925mm. This is my first attempt building a deck - I'm very much still learning and happy to be corrected on any of the assumptions I've made below.

I'll be building this deck directly on top of the existing tiles on my balcony, and do not intend to modify/remove/drill into these tiles. I'd like to keep the total height of the deck <100mm, to avoid creating issues with the height of my existing balcony railing, and the height of my windowsill/doorframe. The BBQ stand/aircon cover pictured below currently finishes 100mm exactly below the height of the railing - this will be placed on top of the deck.

My plan is to use 'Builder's Edge Pedestal Foot 25-40mm' in place of posts and bearers. These will be secured to the tiles with silicone, with the joists secured to them. As I understand it, this product can be lowered to a total height of 25mm. (Please confirm?)

https://www.bunnings.com.au/builders-edge-25-40mm-pedestal-foot-minifoot_p2450073

I will then attach a 45mm high joist on top of this. The joist will be 70mm wide, laid flat - is this appropriate? Will this cause standing water issues?

Finally the decking - 90mm x 19mm, which will give me a total height of approx. 89mm. What spacing is best between these boards to aid drainage?

I've mocked up the below floorplan based on my (very fresh) understanding of how the joists should be laid out. I'd love some feedback on this layout and my suggested approach to ensure I'm on the right track.

Images:

1. Layout of the pedestal feet. The spacing between each joist horizontally is 430mm. The spacing between the feet vertically is 515mm. I know I need to keep the horizontal gaps between joists smaller than 450mm, but do I have too many supports vertically? (is 515mm too small of a gap? Can/should I go bigger, and use less pedestal feet?)

2. Layout of the joists (Feedback appreciated!). Note the deck is built around an existing AC unit.

3. Finished deck design. BBQ stand to be placed back in position to hide the aircon.

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Comments

DoSimpleBetter

Additional context:

- I've opted for a 'proper' structural deck over the alternatives for a couple of reasons: I need 25mm of clearance underneath for a pipe, having it raised will aid drainage, and I want it to be solid enough to exercise on.

- (Why am I building such a small deck on my existing balcony?) I've got a larger plan for the space - I'll be breaking it up with some pebbles, pavers, and a small grassy area for my dog. This section of decking will be in the sunny spot of the (east facing) balcony, creating a nice seating / BBQ area.

Screen Shot 2020-08-14 at 3.23.20 pm.png

MitchellMc

Welcome to the Bunnings Workshop community @DoSimpleBetter. It's great to have you join us and many thanks for your questions.

This sounds like a fantastic project!

You are correct that the minimum height the Builders Edge 25-40mm Pedestal Foot Minifoot can be adjusted to is 25mm high.

In regards to creating a drainage issue, I can't see that being a problem as you still have the 25mm gap clearance from the feet all around. Standard spacing between decking boards is 3-4mm for 90mm boards and 5-6mm for 140mm boards.

I thought I'd mention that balconies do not have an infinite amount of weight they can carry. With every fixed addition like the deck, the pebbles and pavers you will be reducing the overall weight it can subsequently support. The weight it's designed for might be in the vicinity of 200kg/sqm and you are not likely to come close to that, however, with these additions and a party of 10 guests you could potentially run into some issues. I just want to make sure you are aware of this moving forward and considering it when adding significant weight like the pebbles.

I trust you'll have plenty of interest in this project and I certainly think you are on the right track. We look forward to seeing your progression and please do keep us updated.

Mitchell

DoSimpleBetter

https://www.workshop.bunnings.com.au/discussion/comment/9604#Comment_9604

Thanks very much @MitchellMc!

A quick clarification (potentially a silly question) - is 25mm the total height of the pedestal at it's lowest adjustment? (Just wanted to make sure it wasn't a ~20mm base + 25mm-40mm adjustment on top)

- Nic

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/67096#Comment_67096

@DoSimpleBetter,

The pedestals lowest adjustment is 25mm above the ground. 25mm is the height at which the timber will sit on the pedestals lowest adjustment above the ground.

I hope that makes sense.

Mitchell

DoSimpleBetter

https://www.workshop.bunnings.com.au/discussion/comment/96353#Comment_96353

Perfect, thanks very much Mitchell! Gives me the confidence to order them online.

DoSimpleBetter

My main remaining question: have I factored in too many of the pedestal 'footings' vertically? (I'm using 24 total for a very small deck).

I've placed one every 535mm holding up each joist - could I get away with making that gap 800mm-ish instead?

My main concern was the thickness of my joists - 45mm high, 70mm wide (laid flat)

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/9613#Comment_9613

Hi @DoSimpleBetter,

Your bearer and joist design is something more akin to an internal stud wall so it's difficult to determine whether you are using an appropriate amount pedestal footings. I've added an image below of how a standard deck would be constructed and as you can see it specifies for a total of 6 footings. I'd question its estimation that the 70 x 45 can span the 1.8m odd meters between the footings and believe it should have another run of footings in the middle. Even so, as you can see a traditional deck would require 9 footings, this is far less than what you have planned for.

I believe you could reduce the amount you are using and running one row through the centre should be fine as pictured below. You might like to reduce the amount utilised on the top and bottom run also.

Mitchell

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