How to drain water under a low-level deck?

dynaryu

Hi,

I installed a low-level deck (timber frame with composite top) under the clothesline, which is located next to the colorbond fence. For the installation of the timber frame, I removed some dirt so the ground under the deck is lower than around the deck. When it rains, I noticed that water was not draining well, and a puddle was created under the deck. I'd like to get some advice on how to drain water effectively. Thanks.

 

MitchellMc

Welcome to the Bunnings Workshop community @dynaryu. It's a pleasure to have you join us, and many thanks for your question about deck drainage.

Just to clarify—have you already laid the decking boards on top of the frame? That’ll make a big difference in terms of what can be done now. It’s much harder to retrofit proper drainage once the deck is finished, so knowing where you're at with the build will help shape the right advice.

Generally, when building a low-level deck, it's really important to plan for good drainage under the structure. One common approach is to excavate around 200mm of soil beneath the deck area and replace it with drainage gravel and a layer of filter fabric. That setup helps water pass through easily and prevents it from pooling on compacted soil. Alternatively, shaping the soil so that it slopes away from the deck or installing a drainage line to redirect water are also effective solutions.

If the deck is already completed, it may still be possible to address the drainage issue, but the options might be more limited or require working from the sides.

Please let me know if you have any questions.

Mitchell