Low-level Merbau deck with French drain

[melbs]

This low-level Merbau deck required some excavation to make room for drains and the frame.

• The project
• Materials and budget
• Preparation
• Drainage
• Ledger board
• Frame
• Joists
• Decking
• Decking board installation
• Completion
• Before and after
• How to build a low-level deck
• More inspiration for your decking project

The project

I built a deck that sat flush with my back door, a task made difficult with a clearance of only around 150mm from step to ground. Here is how I did it.

Materials and budget

• 10mm DynaBolts (galvanised)
• 10mm coach screws (galvanised)
• 10mm hex bolts (galvanised)
• 100 x 100 x 105mm M10 galvanised angle bracket
• 200 x 45mm treated Pine (doubled for frame)
• 90 x 45 treated Pine (joists)
• Pryda half-stirrup post anchors
• Pryda nails (for joist hangers)
• Pryda joist hangers
• Macsim 8G deck screws and Macsim Clever Tool (highly recommended)
• 90mm Merbau decking boards
• 35-40 bags of concrete
• G-Tape and Protectadeck timber protection tapes
• Deck spacers.

Total cost: around $4500.

Preparation

• Removed existing porch cover and cut down tree
• Excavated an additional 200mm of soil, giving myself about 350mm of total clearance.

Drainage

• Dug trenches and installed a French drain, plumbed into an existing storm water connection (lucky)
• Laid geotextile fabric to help keep the slots on the agi pipe from being clogged with dirt
• A thin layer of scoria between geotextile and agi pipe also assists in keeping the dirt out.

 

Ledger board

• Sets the height of the whole deck (remember to deduct the thickness of the deck boards!)
• 10mm DynaBolts were a bit of overkill
• Be sure to have already marked where the joist hangers will be so that the bolts don't get in the way.

Frame

• 200 x 45mm Pine for frame. Double thickness (200 x 90mm) and joined using timber glue and batten screws
• Dug the holes for the posts/stirrups
• Dropped the bearers into place and screwed together using galvanised angle brackets 
• Using three car jacks, carefully adjusted the frame to be perfectly level and flush with the ledger board
• Screwed the stirrups onto the bearers using coach screws so that they "hang" above the post holes
• Screwed the frame to the ledger board using coach screws
• Filled the holes with concrete and left to set (make sure the concrete has a slight dome shape to allow water runoff).

 

Joists

• Used string lines to mark the position of the joist hangers
• The joist hanger nails are much cheaper than the screws. You must use the special nails or screws from Pryda
• Clamping the joist hanger onto the joist with a C-clamp made it a bit easier
• I used 12 nails per joist hanger.

Decking

• Important: Run a belt sander across uneven areas of the deck frame, smoothing them so there won't be any unevenness when walking on the deck
• If exposed to the elements, use G-Tape and Protectadeck on the frame for protection (this took about 30 minutes with a staple gun)
• 3D printed a jig for guiding placement of deck screws
• Used car jacks to press warped deck boards against deck spacers.

Decking board installation

Best done as a two-person job.

Person 1:

• Uses centreline of jig to place directly under string line
• Pre-drills pilot hole
• Removes jig and uses Clever Tool to drill and countersink hole.

Person 2

• Screws in deck screw.

Completion

• Carefully trim the excess off the Merbau by running a circular saw across each end (I used a clamped piece of timber as a guide).

Before and after

How to build a low-level deck

A low-level deck can pose a range of potential design and installation problems, with challenges around ventilation, drainage, termites and rot. But it doesn't have to be a difficult project once you take the time to understand the basics of how a low-level deck is put together.

Experienced Bunnings Workshop member Adam Woodhams has created a comprehensive guide to building your own low-level deck, which provides an excellent reference for getting started. 

Resident D.I.Y. expert MitchellMc has also put together a step-by-step guide and video tutorial showing how to build a floating deck using adjustable pedestal feet.

More inspiration for your decking project

Bunnings Workshop member oninpena used pedestal feet to support part of a low-level composite deck built across a partially concreted area.

Workshop member Aaron made the most of a tricky space with a Low-level deck using reclaimed timber for a unique finish.

Whether you're building a new deck or rejuvenating an existing one, you can get inspired by the clever and creative Bunnings Workshop community in our Top 10 most popular deck projects and our collection of inspiring low-level deck builds.

Let us know if you need a hand with your own deck project – we're here to help.

[MikeTNZ]

Hi @melbs,

May I just say, you are a legend!

I really like how the colour of the timber suits the brick-work and the whole decking looks like it was meant to be there from the start.

That is simply brilliant.

Top marks!

Cheers,

Mike T.