Lining board for a log house – why is it needed, method of installation

Underlay board under the log house

The underlay board has been used as a timber protection for a long time. Perhaps that is why disputes arose about the advisability of using this method, because there are modern methods of protection against decay.

However, we are sure that additional protection will not hurt anyone, especially since the method is quite simple. In general, after reading the reviews and opinions of experts, we recognize that the majority is in favor of using a backing board as an additional way to extend the life of a wooden structure, be it a residential building or a bath.

Underlay board under the log house

Important! The underlay board is used in one of the most important areas of home construction – the place where the logs or beams come into contact with the foundation.

Let’s emphasize:a lining board, sometimes called a mortgage, is a layer between the foundation and the lower crown of a wooden structure. It is the lower crown that is the first to suffer from high humidity, snow and rain, temperature changes. Most often, a backing board is used if the log house is on a concrete foundation, because condensation can form on it in the morning, leading to the destruction and decay of wood.

Underlay board under the log house

Benefits of using a backing board:

  1. An additional protective barrier appears.
  2. The use of a backing board increases the life of a wooden house.
  3. The board itself can be additionally protected with various antiseptics and fire retardants. This increases the level of protection.
  4. If necessary, it is much easier and cheaper to replace the backing board than the entire first crown. The log house can be jacked up, the planks on the foundation can be replaced and the building can be used again. We admit that this method of replacing a backing board is only suitable for a relatively small building..
  5. It will be more convenient and reliable to attach the drainage to the underlay board. This will prevent the metal fasteners from contacting the log in the place where the moisture will be clearly increased..

As for the optimal version of the backing board, this is larch with a size of 150×50 millimeters. Such a “fifty” made of larch is quite comparable in strength to oak, this tree is not afraid of frost and moisture, temperature extremes and rotting, but it is more difficult to process, and the cost is slightly higher than traditional pine.

Underlay board under the log house

Also, larch burns twice as bad as pine. Edged larch board now costs 21-46 thousand rubles per m23. We are talking about fifty (for a backing board this is the best option), 100-200 millimeters wide.

If larch is too expensive for you, choose relatively inexpensive pine. Its price will be about 7.2 thousand rubles per cubic meter. The difference is palpable, but the pine will have to be treated a little more carefully with antiseptics and fire retardants.

Underlay board under the log house

The very process of laying the board on the foundation is simple: a layer of insulating material is laid, for example, an ordinary roofing material in two overlapping layers, then the board itself is placed, which is attached to the foundation with anchor bolts. They should go into the concrete base of the foundation by four to five centimeters, and the caps should be completely buried in the wood. Place a layer of insulation on the board, such as hemp or moss.

Underlay board under the log house

In general, the backing board will serve as a zero crown, which, if necessary, is much easier to replace than logs. Whether to use this method is up to you.

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