Why does timber rot, and what actually causes wood to decay in old buildings?In this second episode of our Talking Conservation timber series, Rich and Stephen dig into the real reasons timber rots, and why it is not simply a case of “old wood going bad”.

We explore the role of moisture, fungal growth, ventilation, drying, and environment, and explain why understanding these basics is essential before you can diagnose or fix any timber problem properly.

We also look at how moisture meters work, why they can be useful, how they can be misleading in the wrong hands, and what early warning signs to look for if you are worried about rot in your building.

If you own, manage, or work on an older building, this episode will help you understand why timber decays, how to spot the conditions that allow rot to thrive, and what practical steps can help prevent it in the first place.

In this episode, we cover:

- Why timber rots in old buildings

- How moisture meters work, and how to interpret them properly

- Why timber moisture content matters

- The four conditions fungi need to grow

- Why rot is about environment, not just age

- Ventilation myths and the importance of airflow

- Why forced drying can sometimes make things worse

- The word “Breathability” (Rich’s pet hate), hygroscopicity, vapour permeability and capillarity

- Early warning signs of timber decay

- Why understanding moisture paths is key to prevention

- This episode sets up the next part of the timber series, where we will look in more detail at wet rot, dry rot, soft rot, misdiagnosis, and chemical treatment.

Listen to the rest of the timber series:

Episode 1, How Timber Works in Old Buildings

Episode 3, Wet Rot vs Dry Rot, What’s the Real Difference? coming soon

Talking Conservation is the podcast all about the conservation of old, traditional, and historic buildings and sites. Don’t forget to like the podcast, subscribe to the channel, and hit the notification bell so you don’t miss the rest of the timber series.

Useful links

Expertible, book a 1:1 call with an independent expert:

https://www.expertible.com

Stephen’s conservation training and CPD:

https://www.beconservation.com

https://www.thebesttraining.co.uk

Timestamps:

00:00 Music intro.

00:04 Intro to subject, why does wood rot?

02:16 Moisture meters, to use or not to use?

15:21 Moisture danger zones.

17:52 What fungi need to grow.

21:39 Expertible

22:22 The rapid spread of rot, myth or not?

25:19 The spores are omnipresent, should we be worried?

25:37 Is ventilation the ‘silver bullet’?

30:01 The physics of drying: stage 1 and stage 2.

33:56 ‘Breathability’, a term that gives Rich the ‘ick’!

36:43 What to look out for; signs of rotting timber.

44:18 BE Conservation

45:00 Finding concealed rot by probing and micro-drilling.

49:23 Can I analyse timber rot for myself?

50:30 Can dogs smell out rot?

53:10 Review of episode.

55:20 The importance of maintenance and understanding your building.

56:45 Episode wrap up and teaser for next episode.

58:31 Outro music.