Not much moves the price of a garden room more than materials, and a few things are shifting this month. Here is what is happening to build costs and specification, and what it means before you sign a quote.
Softwood timber prices have firmed through 2026
Timber market reports through the first half of 2026 point to softwood prices holding firm to higher on tighter supply, with benchmark lumber indices climbing rather than easing as many expected. Structural framing softwood is the backbone of most garden room builds.
For a buyer that means the timber-frame line on a quote is unlikely to fall this year, and may creep up. It is a reason to get firm, written quotes now rather than waiting for a dip that the supply picture does not support, and to ask whether the price is held for a set period. See the timber market report.
Wider material inflation feeds into build costs
Official UK figures put construction material prices up 3.2% in the year to April 2026, with aggregates (gravel, sand and clays) up 7.7% and fabricated structural steel up 8.5%, though cement fell 4.5%. Bases, fixings and any steel elements all sit inside that basket.
A garden room is more than its timber, so these movements matter for the groundworks and base as much as the cabin. When you compare quotes, check that the base and foundations are specified and priced clearly rather than left vague, because that is where rising aggregate costs quietly land. Read the DBT commentary.
Thermally modified cladding goes mainstream
Trade and design coverage this year has thermally modified timber, often sold as ThermoWood, moving from a specialist choice to a default cladding on premium garden rooms. The modification process cuts moisture absorption and removes the need for chemical preservative treatment.
If you want a garden room that weathers predictably with little upkeep, it is worth asking about, but it carries a premium over standard cladding, so weigh the lower maintenance against the higher upfront cost. Ask the installer how it is fixed and finished, as hidden fixings and end-grain sealing are what make it last. More on 2026 cladding choices.