Most new build buyers spend hours thinking about the kitchen, the bathroom finish, the garden layout, and the colour of the front door. Far fewer give a second thought to the timber holding the whole thing together. Yet the floor joists beneath your feet, the rafters above your head, the sole plates at the base of every wall, and the cladding on the outside are all timber, and the way that timber is selected, treated, and installed has a direct bearing on how long your home will stand up to the weather, the seasons, and time itself.

That’s why the National House Building Council dedicates an entire chapter of its Standards to timber preservation. Chapter 3.3 of the 2026 edition sets out exactly how natural solid timber should be protected against fungal decay and insect attack across every part of a new home, from internal skirting boards to external decking posts.

What makes timber preservation so important, and so easy to overlook, is that almost all of it happens before the house is finished. By the time you walk through the front door for the first time, the treated timber is already buried inside walls, hidden under floors, and tucked into the roof void. You can’t see the certificates, you can’t smell the preservatives, and you can’t tell at a glance whether the right species was used in the right location.

The NHBC chapter sets out a system of Use Classes that rate timber by how exposed it is, alongside Desired Service Life expectations of typically 60 years for structural elements and 30 years for external joinery. It then specifies, component by component, whether each piece needs preservative treatment, naturally durable heartwood, or both. Get any of those decisions wrong, and the consequences may not show themselves for years.

In our experience, the vulnerable points are usually the obvious ones once you know what to look for. Cut ends of treated timber that haven’t been re-coated, deck posts sitting too close to the ground, external joinery starting to swell after only a few months, or corrosion staining where metal fittings meet treated wood. None of these are catastrophic on day one, but each one signals a process that, if left, will keep developing.

A snagging inspection won’t replace a full structural survey, and it won’t tell you what’s behind the plasterboard. What it will do is pick up the visible signals that the standards haven’t been carried through to the finish, and give you something concrete to put to the developer while they’re still on the hook to put it right.

Read the Full Guide

We’ve put together a plain-English walkthrough of NHBC Chapter 3.3, breaking down each section so you can understand what your developer should have considered, why it matters, and what to look for in your own new home.

Read our full guide to NHBC Chapter 3.3: Timber Preservation →