How to impregnate structural wood? Structural timber can remain unchanged for many years, maintaining the structure of the roof. For this to happen, they must be thoroughly impregnated beforehand. What methods will prove to be the most effective in this? What are they about?
How to prepare structural timber?
Before starting the impregnation, the construction lumber should be stripped of its bark. The surface should be straight, without infiltrations, discoloration or holes. Their presence is a symptom of the presence of fungi and pests. The wood should also be thoroughly dried. The correct humidity ranges from 15 to 18%.
Studies show that wood with a moisture content above 30% is characterized by 60-75% less strength. This applies primarily to bending. Wood deprived of water is more susceptible to mechanical damage. Another factor that determines the strength of wood is its processing. A better choice is hewn or planed wood. Its surface is smooth and consistent. In this way, it is less exposed to moisture and insects than wood straight from the saw.
What is worth knowing about wood impregnation?
Securing wood yourself is very demanding. Therefore, it is better to entrust this task to specialists. Another solution is to buy impregnated wood. To make it easier to recognize the degree of protection, it is usually painted green. Before buying, it is worth checking what materials and methods were used.
Several methods of impregnation are available. If they are recommended by the manufacturer of the protective preparation, they are effective. To achieve the intended effect, follow the manufacturer’s instructions carefully. First of all, those regarding bathing time, consumption standards or proportions of the agent.
What is pressure impregnation?
Pressure impregnation is primarily used for surfaces that are at risk of fungal growth (e.g. directly in contact with the ground). It is made in autoclaves, where under increased pressure, the impregnation penetrates deep into the wood. As for parts with a small cross-section, it can penetrate them completely.
In the case of thicker elements, it penetrates to a depth of several millimeters. Impregnation takes no more than several minutes. Pressure impregnation is designed to protect elements of the truss and garden architecture.
Due to its properties, it is very popular. It is characterized by poor washability. What does it mean? After the preparation is fixed , the construction wood can be temporarily outdoors after two days. Salt impregnations are mainly used.
What is an impregnation bath?
Another type of impregnation is a bath. It consists in completely immersing the wood in a bath containing an impregnation solution. The bathing time is specified by the manufacturer. In sawmills, large tubs are designed for this purpose, into which logs or scantlings are placed mechanically. In the case of self-treatment, however, it is relatively expensive, and therefore unprofitable. Firstly, because a large container is necessary, and secondly, a large amount of impregnation. Its remnants must then be disposed of safely.
During the bath, the ingredients of the preparation are absorbed into the wood, and the water contained in it is transferred to the impregnating solution, diluting it. To avoid excessive dilution, the density of the fluid should be constantly monitored. If necessary, refill the impregnation.
This method allows you to protect the wood to a depth of several to several dozen millimeters. This is sufficient to protect the wood for structures inside the facility. This method uses salt impregnation that can be washed away by rain. To avoid problems, it is recommended to store the wood under a roof or use it immediately after impregnation.
What is painting and spraying?
The effectiveness of this method depends primarily on the agent used and the number of layers. Impregnation can be done in two ways. Firstly, rubbing the preparation with a brush or using a spray device. In order not to waste the product, it is better to measure the amount needed and then spread the whole thing. One painting or spraying is not enough.
So how many layers to apply? It depends on several factors. First of all, the structure and parameters of the wood, as well as its ability to absorb the preparation. Most often, however, 2 to 8 layers are enough, which should be applied, taking into account the intervals recommended by the manufacturer. During this time, the water or solvent introduced into the wood can evaporate freely.
Apply the first layer generously. Make sure the wood is well soaked. Then we wait until the preparation is absorbed. The next layer is applied when the impregnation is completely absorbed by the wood.
Thanks to the next layers, the degree of penetration of the preparation increases, i.e. it penetrates into the deeper layers of the wood. This method uses both water and solvent impregnation.