Technical>Building physics

Timber buildings: how long do they last? (Part 1)

One of the most common questions we are asked is this: “How long does a wooden building last?”.

The answer of the question is complex and related to various aspect of the building process, mainly including the design. The durability of a timber structure can be compromised, but why does it happen? For an intrinsic physical limit of the material or are other factors that determine a considerable reduction of the life of the building? Does a careful study of the construction details help?

Before answering these questions it is better to clarify some concepts: wood is a material with very specific physical characteristics. In fact, it has almost zero thermal expansion, it is resistant to acid, it performs very well in case of an earthquake but … it can not tolerate water stagnation over time, especially if this accumulation occurs on the head where the fibers are totally exposed. The simultaneous presence of water and oxygen creates an optimal environment for the development of fungi, mold and other wood-eating organisms. In a short time, days or weeks, they can eat even the load-bearing structural parts.

The european code (EC 5) requires to ensure a nominal life for residential buildings of at least 50 years and, in order to guarantee this result, it is necessary to take care of all the details.

Is it better an active protection system or a passive one?

Can we entrust ourselves totally to the efficiency of the membranes over time or is it better to study the details such as to prevent stagnation of water?

 

2012-06-06 10.10.41

The vast panorama of EN regulations does not help much to solve this problem and also the books dedicated to this subject are not always sufficiently comprehensive and complete. Nevertheless the issue of durability is one of the most important question to deal with when you are designing a wooden building.

For this reason a careful study of every construction detail is necessary: in a building there are dozens of them but one of these is undoubtedly the most important. We are talking about the connection on the ground or the point where the wood is closer to the ground where there could be a water stagnation.

(the skrewdriver it’s been inserted into the CLT bearing wall without using hammer)

All the buildings in these photos have had problems with the ground connection detail and the causes have to be searched in some design and/or realization mistakes.

Ergodomus is specialized in the design of timber building since more than 10 years, contact us and we’ll help you with your projects.

The detail of the connection to the ground must be designed correctly and it must meet three requirements simultaneously. They are:

  1. Durability
  2. Static
  3. Building physic: “Absence” of thermal bridges and condensation

We then add a fourth: to respect the architectural appearance of the building planned by the designer. Of course we must not forget the economic aspects!

What kind of solutions can I take?

How can I ensure that these conditions are met in such a delicate part of the building? What are the principles to be followed to avoid any mistakes and to guarantee warm, secure and comfortable homes to our customers over time?

First of all it is necessary an accurate study of every detail! But, as you know, during the building’s life there unpredictable things can happen. So how can we be sure about the durability of our building?

To answer at the last question, there’s a product which constantly monitor the health of your building. This allows you to intervene promptly to prevent any problems on timber walls and slabs: the name of this product is Wood Control and the last January we interviewed the fathers of this clever system

We publised this article also on LinkedIn LinkedIn_50x50 in order to be able to answer to your questions and start a discussion reading your point of view. Perhaps we can even manage to answer to the first question…

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