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How to build floating boardwalk over drainage trench using pallets?

Hi everyone,
I’m looking for advice on a low-cost, temporary solution for this drainage trench I’ve dug to prevent flooding in our garage/storage area.

For context: we bought the house last year and discovered significant drainage issues caused by poorly planned site works and vegetation clearing that were done purely for cosmetic purposes before the sale. The pool itself isn’t the issue, but the site works have resulted in water flooding our garage (a converted shed). The slab of the garage is about 150mm lower than the pool and surrounding ground, and the garage was finished with external plasterboard walls, just to give you an idea of how dodgy the conversion is.

The trench is a solution to stop water pooling and flooding. It’s quite deep, as it needs to carry most of the water from the site, including roof runoff that discharges directly to the ground due to the age of the house. Its far from ideal but its working. At the moment, it’s lined with mid-range weed mat from Bunnings to stop it becoming a mud pit for our two active dogs. The trench cuts across the path to our house and runs through the main yard where everyone plays, making it an eyesore and a hazard.

Here’s my idea (inspired by the last photo I’ve included):

1. Fill the trench with drainage gravel to create a level surface while still allowing water to flow and drain effectively.

2. Use pallets (coated with paint bitumen underneath for slightly more longevity) to create the base of a floating boardwalk.

3. Lay decking timber across the pallets (running longways for ease) to tie them together and create a stable, usable surface.

From what I’ve learnt from here and YouTube, this might just work if I can get the details right. Keeping in mind I only need it to last 2 years.

I’ve attached photos of the trench and the two types of pallets I have access to (labelled A and B).

I don’t know whether these are hardwood or pine – can anyone tell from the photos?

Which style (A or B) would be better for this project?

I’m considering cutting the pallets back to the centre support (as marked in the photo of pallet B) to make the path narrower and reduce decking timber costs. Is this viable, or would it compromise the stability of the structure?

My concerns/questions:

Am I dreaming? Will this even work as a functional, temporary solution?

Part of the boardwalk will be over the 'embankment' where the soil now slopes significantly away from the pool and garage to carry away water, will 'leveling' with gravel maintain the underlying slope?

Is drainage gravel even the best option? I do have a heap of approx 20- 30mm rocks i could use but assume these would not give a stable 'pad'?

What is the longest length decking timber comes in? I’m planning to run the boards longways for simplicity and to minimise cuts.

I want to avoid a dry creek bed because our dogs will likely make a mess of it, scattering small rocks. Plus, rocks in the grass beside the glass pool fence sounds like a recipe for disaster when mowing.

Any suggestions for how to finish the curved area in the corner of the trench? I’m undecided on the best approach here.

I’m aware of the need to be careful near the pool fence to avoid altering the ground height and impacting compliance with safety regulations.

I’d love to hear your thoughts and suggestions – I want to make sure this will work before I commit to it. Thanks so much for your help!

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Comments

MitchellMc

Hi @Ona-Budget,

Your floating boardwalk idea is quite creative but comes with challenges, particularly given the environment you’re working with. The pallets shown in the photos appear to be pine, which won’t hold up well in a moist environment, even with bitumen coating. While they might last the two years you’re hoping for, there’s a good chance they could rot or weaken faster due to constant exposure to moisture. Hardwood pallets would perform better, but they’re less common. Of the two styles, pallet B looks more robust and better suited to the project.

Filling the trench with drainage gravel to create a level surface is a practical idea and would allow water to flow through effectively. To maintain the slope of the trench while levelling the gravel, you’ll need to compact the material carefully and ensure it follows the existing gradient. If you have a supply of 20–30mm rocks, you could mix them with the drainage gravel to add stability, but rocks alone wouldn’t provide a firm enough base for the pallets.

Grass, as an alternative to the boardwalk, could also work well for a temporary solution. You could fill the trench with gravel, top it with soil, and seed it with grass. This would allow water to filter through while creating a low-maintenance, durable surface that blends with the yard and eliminates the need for a boardwalk.

The longest standard lengths of decking timber are usually 5.4 metres, but it’s worth checking availability at your local store, as this can vary. Running the boards longways is a sensible approach for simplicity and to minimise cuts. For the curved section of the trench, you could use shorter decking pieces cut to fit the curve or a flexible edging material to create a neat finish.

Addressing the root cause of the drainage issue might be a better investment of time and money. Installing agline or a pit and piping the water to your stormwater system would provide a long-term fix rather than a temporary cover-up. While it’s a bigger project upfront, it would prevent flooding, avoid ongoing maintenance, and improve the property’s overall functionality. If you can share more about the two-year timeline—such as whether you plan to sell or renovate further—it might help refine the best course of action.

Let me tag @Nailbag and @Dave-1 for their thoughts.

Please let me know if you have any questions.

Mitchell

Dave-1

Morning @Ona-Budget

Having a think about your drainage issue and going back a couple of times sorting some ideas in my head.

I wouldnt be using the pallets as a temporary base for a deck 😕 Pine pallets will definently degrade and loose their structual strength and you will end up having to try and fix something.

I do like your idea for the temporary walk way, You could go down the track of using the TuffBlock 300 x 300 x 90mm Instant Foundation System Deck Support to support the bearers and go with treated pine to support your deck. (when you go to do the permanant deck you can reuse these) I would also make the path 900mm wide, 840mm ish is around a doors width and having people try and pass on less is problematic.

I would actually go the route of installing 100mm socked ag pipe in your temporary channel and backfill with drainage gravel 5mm-8mm sizze (keeping a slow fall to the trench towards where you want the water to go. (not sure how high you are above the gutter on the road but as you have said the downpipes are not connected) This way you wont need to redo the drain.

I would put in the hard work on the way towards the deck you want one day. Drain sorted, drainage sorted and not spend a lot of resources on a temporary fix. If part of the temporary fix can be done as a permanant fix then yes. If you list the permanent fixes you might end up with a whole project, it will just talke a little longer.

As a temporary work through as you have that trench and landscape work I would use those pallets vut down so they are at least 800mm wide and pretty much lay them on the ground end to end (lift the tops and then replace them so they are side by side and you may need more supports as that time of pallet strips arnt that strong) It will give you a path at least short term.

Dave

Nailbag

Hi @Ona-Budget

again at the risk of popping your balloon of inspiration I would have to agree with both @MitchellMc and @Dave-1 in using the pine pallets. There is so much more to consider as @MitchellMc outlined. And in your case, the effort in putting together your project even on a super budget is going to be money not so well spent.

I like the idea of @MitchellMc with the grass as the overlay, but instead of real grass, utilising artificial. Bunnings have quite a range of affordable types that once you follow his drainage instructions, would allow you to almost just roll it out and fix it down.

Nailbag

Ona-Budget

Thanks, everyone!

I took your advice and scrapped my original idea. I hadn't even considered covering the trench with soil as an option! I completely agree that proper drainage would be the best long-term solution, but given the scale of the works (it's the entire site, including downpipes discharging to ground) and the financial commitment, it's just not something we can tackle right now.

As suggested, I backfilled the trench with gravel I already had, then covered it with landscaping fabric from the builder's section at Bunnings before topping it with soil. I had some 400×400 travertine pavers left over from the previous owners’ pool coping, so I alternated them with 600×400 travertine pavers from Bunnings. Eventually, I plan to extend these to the deck stairs.

On Sunday, I picked up the last couple of turf slabs, but there weren’t enough to complete the curve to the corner of the pool—I'll get to that in time. For now, I’ve covered the area with mulch to help suppress weeds.

I’d love to add some tropical, pet-safe plants—if anyone has suggestions! I love the look of Xanadu, Cordylines, and Bromeliads, with maybe a feature palm. However, since Cordylines, Xanadu ans some palms are toxic to dogs (and mine think they’re cows and will graze on anything), I need to find safer alternatives that will give that tropical vibe and fill out quickly. Any recommendations?

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/48599#Comment_48599

Afternoon @Ona-Budget

Looks good and love the style of pavers! Love the staggered look, it does the job and dosnt look cold and exact 🙂

Sorry cant help you on what plants to put in, I always forget about the names of stuff I put in within days and tend to go for trees 🙂

Dave

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/48599#Comment_48599

Great work @Ona-Budget! That looks fantastic, and I love the curved area. I'd add a boarder to make trimming easier and leave it as is.

Consider plants like the Areca or Bamboo Palms, which has feathery fronds and is safe for pets, which also provides a tropical look. The Spider Plant is another good option, known for its long, arching leaves and ease of care. You could also try Boston Ferns in shaded areas, which thrive in a tropical environment and are non-toxic to pets, or the Calathea, which offers stunning patterned leaves and is safe for dogs. The Parlor Palm, a hardy and attractive option, and the Prayer Plant with its vibrant, patterned leaves are also great choices. For pops of colour, pet-safe flowering plants like African Violets or Impatiens would add extra charm. These alternatives should give you a tropical look while keeping your dogs safe and happy!

Mitchell

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