The durability of the roof structure depends, among other things, on whether it has been properly protected. Otherwise, the roof truss may become damp, warped and cracked, and it will be vulnerable to pests, fungi, mould and deterioration. To protect the roof structure, it must be properly weatherproofed.
It’s best to weatherproof the roof structure as early as during the construction stage of house. Thanks to this, we can protect the wood for a long time. In case of a roof renovation, it’s worth checking the condition of the wood in the truss and fill in any gaps if they are present. Then, we can weatherproof the existing truss and protect it for the following years.
At this point it’s worth noting that the preservative works best with dry wood – wet material will struggle with absorbing the preservative, may even not take it in – the wood moisture can’t exceed 18%. Because of this, we should invest in dry wood. Working with weatherproofing of wood for the roof structure should be carried out when the air is dry, at a temperature of 5 °C to 20 °C.
Several types of wood preservatives are available on the market, which are preparations suited for different needs:
salt preparation – available in the form of a powder or solution – penetrates the wood structure easily and deeply – applied with pressure or immersion method – however, this preparation is washed out by water – it can’t be used to protect elements, which are exposed to contact with water – e.g. a sheet-metal roof, but it can be successfully used under a material that is not vulnerable to corrosion,
water-dilutable preparation – construction preservative, commonly used for roof structure – dries quickly, doesn’t emit a strong, unpleasant odour, it can be applied, for example, to a surface that has been previously protected with a salt preparation – it can be used under any type of roofing material, it’s resistant to even the most adverse weather conditions,
solvent preparation – its advantage is that it absorbs into the wood faster than water-dilutable products, but it also has a major disadvantage – it’s a toxic material and won’t work in a situation where the loft is planned to be inhabited,
oil preparation or stain varnish – they form a protective, waterproof surface, but they shouldn’t be the main means of protecting construction wood – used e.g. for roof truss.
Of the above-mentioned measures, we can perform roof structure weatherproofing by ourselves using a liquid preparation, applying it manually with a brush. The wood for the roof truss can’t have bark, any holes, discoloration and stains. If there are any, we need to remove them. Before proceeding with the weatherproofing, the wood should be dried.
If the wood is properly prepared, you can proceed with its weatherproofing. Depending on the type of wood and its properties, 2 to 8 layers of the preparation should be applied. Special attention should be paid to the fact that the first applied layer has to be the thickest, and the subsequent ones – appropriately thinner. The drying time for each layer must also be strictly observed.
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