For Containment Level 3 (or BSL3) and above or cleanrooms, air-changes will increase further still, often becoming impractical for an office conversion.

With engineered timber overall deformations are less likely due to the controlled material use and grain directions, but it is still sensitive to swelling if exposed to moisture and water.This makes it necessary to adequately waterproof the envelope of the building and protect the material during transportation and construction.. Due to high demand, timber sold in the UK is typically not dried out properly.

As it dries it changes geometry losing original accuracy.This is a problem as connections cannot be relied on geometrically and presents a challenge particularly for DfMA solutions and other situations where small tolerances are required.. Our response is to:.- Transport and store timber in waterproofed flat stacks.. - Engage early with contractors to produce an on-site maintenance plan with special attention to timber elements.. - Enable sufficient drying periods within the project programme.. - Use preservative natural treatments to prevent woodboring and avoid the use of toxic chemicals such as chromium, chlorophenols or arsenic.. - Use preservative natural treatments on all sides to prevent water ingress.

Oil based primers penetrate wood better than latex or water-based primers, providing greater resistance and are less likely to be scraped off during construction.. - Consider design details to prevent water ingress during construction and use.. Fire and insurance.Since the Grenfell tragedy, public policy has shifted towards a zero-combustibility approach in certain higher risk buildings, making the use of engineered timber more complicated.

This has increased insurance costs for mass timber construction.

It is common practice to solve the problem by enclosing timber for increased fire protection.But is off-site always the best way to achieve these benefits?

Construction sites have been around since the dawn of civilisation.Do we really want to walk away from all that learning, and start moving as much of the construction process as possible into distant sheds?.

Is on-site construction really all that bad?.Construction sites could be defined as locations where finished assets are built.