Material Moisture - General Principles

There are a number of materials used in construction that can be significantly affected by their own Moisture content, as well as impact on the ability to bond to other materials. This is fundamentally different to materials that get wet/are water damaged. Moisture content is referring to a material that contains a variable amount of moisture within the material itself a part of the composition of the material.
Predominantly this includes;

• Timber – before being cut down to process into timber, a tree has a moisture content of up to 90%, but after the tree is cut down the tree no longer draws water into the timber and continues to “dry out” for many years. The tree is processed into various sizes of timber for construction works. As the timber dries out, it shrinks. Depending on a number of factors during this process, such as species of tree (hard or soft wood), the size of the timber (200 x 200mm will be less affected than a 200 x 50mm) the timber may split, warp, cup or bow
• Concrete – Concrete is a “wet” product initially; in that dry materials are mixed together using water, the mix is then placed and finished, and the concrete begins to “dry” out or “set” (cure) into a hard product. The concrete continues to dry until it is sufficiently “cured” for the application of finishes like sealers, glues for vinyl, line marking paint etc.
• Render – similar to concrete, render is applied as a “wet” mix. The moisture in the render is drawn into the porous dry block work, allowing the cement to bond to the block work. The render continues to dry until it has sufficiently “cured” for the application of finishes like paint.