Treated Pine Fence Plinths: 150×25mm and 150×38mm Buying Guide

A fence plinth — sometimes called a bottom rail or base board — is the horizontal timber that runs along the bottom of a paling fence, sitting between the posts just above ground level. It keeps your palings off the soil, prevents moisture wicking, and gives the fence a clean, finished look. At Wallan Fencing and Timber Supply, we stock treated pine fence plinths in two sizes: 150×25mm and 150×38mm, both in 5.4m lengths.

What Does a Fence Plinth Do?

Without a plinth, paling fences tend to rot from the bottom up. Palings that sit directly on or near the ground absorb moisture, attract termites, and deteriorate quickly — even treated pine. A plinth lifts the palings clear of the ground and provides a solid base to nail or screw them to, keeping the fence line straight and the bottom edge uniform.

Plinths also make the fence easier to build. Rather than trying to set every paling at exactly the same height, you simply rest them on the plinth and nail off — the result is a perfectly level bottom line every time.

150×25mm vs 150×38mm: Which Should You Use?

150×25mm Plinth

The 150×25mm is the standard residential plinth. At 25mm thick, it's strong enough for most domestic fencing applications and is the most common choice for new timber paling fences across Mitchell Shire. It's lighter and easier to handle than the 38mm version, which makes it popular for DIY projects.

Best for: Standard residential paling fences, DIY builds, budget-conscious projects.

150×38mm Plinth

The 150×38mm is a heavier-duty option. The extra 13mm of thickness gives it significantly more rigidity and resistance to bowing over long spans — particularly useful on longer fence runs or where the ground is uneven. It's also better suited to commercial or rural applications where the fence will see more wear.

Best for: Long fence runs, uneven ground, commercial or rural fencing, high-traffic areas.

Specifications

Both plinths are:

• Timber species: Radiata pine, CCA pressure-treated (H3 or H4 rating)
• Length: 5.4m
• Width: 150mm
• Finish: Sawn, green-grey treated colour
• Treatment: Suitable for in-ground and above-ground contact

How Many Plinths Do You Need?

Plinths run the full length of the fence, so the calculation is straightforward:

Number of plinths = Total fence length ÷ 5.4m (rounded up)

For example, a 30m fence run requires 6 plinths (30 ÷ 5.4 = 5.56, rounded up to 6). Allow one extra for waste and cuts.

Installation Tips

1. Set your posts first. Plinths span between posts, so posts need to be in before you fix the plinth.
2. Leave a gap above ground. The plinth should sit 20–50mm above finished ground level to prevent moisture contact. Use a string line to keep it level.
3. Fix to posts with 75mm galvanised nails or screws. Stainless steel or hot-dip galvanised fixings are essential — standard bright steel will rust and stain the timber.
4. Pre-drill near ends. Treated pine can split if you nail too close to the end. Pre-drill within 100mm of any end.
5. Allow for expansion. Treated pine is often wet when new and will shrink as it dries. Don't over-tighten fixings.

Pairing with the Right Palings

The 150×25mm plinth pairs naturally with 150×12mm or 100×12mm palings. The 150×38mm is often used with heavier palings or in situations where the fence needs to resist lateral pressure — such as on sloped blocks common across the Wallan and Kilmore areas.

Available at Wallan Fencing and Timber Supply

We stock both the 150×25mm and 150×38mm treated pine fence plinths at our yard in Wallan, with same-day pickup available. We supply tradies, builders, and homeowners across Mitchell Shire — including Kilmore, Broadford, Seymour, Beveridge, Craigieburn, and Donnybrook.

Get a quote online or call us on 0431 193 102 to check current stock and pricing.