Immediately, we note that the appearance of cracks in drying out logs is inevitable. Any wood decreases in size, gradually drying out. For example, when completely dry, pine will decrease along the fibers by 0.1–0.3%, and across the fibers by 3-5%. And everything would be fine, because it is not so difficult to deal with the shrinkage of log cabins.
However, the dimensions of the inner and outer layers of the log change unevenly! For example, let’s take the same pine – the outer fibers dry out by more than 8%, and the inner ones – by only 2-3%. This is understandable, because the density of the external and internal wood fibers is different. The outer ones give off moisture faster. As a result, the outside of the log is practically dry, but moisture remains inside. This difference in moisture and density leads to rupture of the upper layers, cracks appear.
If the process of cracking in logs is natural and inevitable, is it worth building log cabins at all? Yes, because small cracks are just a net on a log, not a problem for the structure. But expansion of cracks up to 3-5 mm can already lead to serious consequences:
- moisture gets into the cracks, and this can cause wood to rot;
- cracks can be an excellent access point for bark beetles and other wood pests;
- the structure of the tree, the sealant of the log house is broken, deformations are possible.
Despite the inevitability of the appearance of cracks on the logs during shrinkage, there are methods for preventing this phenomenon, which make it possible to avoid large breaks:
- Natural shrinkage, stretched out in time. If the log dries gradually, in the shade, long before the start of construction, the cracks will be much smaller. For example, if the logs dry for only a year, the crack width can reach 6–10 mm, if two – only 1–2 mm;
- End sealing. It is important to remember that the end of the log itself dries up much faster than the rest. It is exposed to active external influences, so shrinkage is intense and cracks appear much earlier than on the log itself. But if you close the moisture outlet through the ends, cracks can be minimized. Special sealants, drying oils, wood varnishes, oil paints are used;
- Compensation cut. It is made specifically to relieve stress in the fibers of the log. Experts themselves decide what kind of compensation cut is needed, it is done along the axis of the beam, along the upper or lower surface. Some craftsmen do not bring the deformation cut to the end, others decide to make it over the entire surface. The cut will be hidden by the lower or upper log, that is, it does not affect the characteristics and type of the log house, while compensating for the difference in voltage, humidity and density. The cut is usually made with a thickness of 7-10 mm and a depth of 1/6 or 1/5 of the diameter of the log.
Important!Some wood experts are wary of compensating cuts. They believe that it is better to dry the wood for two to three years in a stack to minimize the formation of cracks, than to make an extra cut, break the structure of the wood..
Prevention methods help to avoid large cracks, and small ones, according to many experts, do not need to be repaired, there will be no harm to the log house. However, if the crack turned out to be more than 3 mm, you are afraid of the consequences, you can start sealing it. For this purpose, today numerous sealants are used: silicone, acrylic, boutique rubber.
Alternatively, you can use a mixture of sawdust and PVA glue, this is a proven home method. Chips are hammered into especially deep cracks, and after that they cover these places from above for sealing. There are also special putties for wood, but they are used on small cracks – up to 3 mm, otherwise the composition itself may begin to crack.
Another old-fashioned method is caulking cracks with moss, pre-moistened so that it swells and clogs up all breaks.
We state: correct, long-term drying of logs minimizes the appearance of cracks, this is the most reliable way to prevent problems. Therefore, choose logs for your log house competently, thoughtfully, giving preference to those that have been lying in a stack for at least two years. In this case, you do not have to deal with cracks, they will not become a problem..