Why do log homes present sealing challenges?

The log house is an architectural marvel that charms with its organic and robust appearance. However, for a building expert, it represents one of the most complex construction systems to make completely airtight and watertight. Unlike modern lightweight frame houses, where airtightness is ensured by continuous membranes (air and vapor barriers), the log house relies on a "living" material that forms the structure, insulation, and finish all in one.

Here are the main technical reasons that explain why these structures are prone to leaks.

1. The phenomenon of shrinkage and settling (The wood "moves")

Wood is a hygroscopic material, meaning that it absorbs and releases moisture to balance itself with its environment.

• Post-construction drying: A freshly cut log contains a huge amount of water. Even after factory drying, once the house is assembled, the wood continues to dry for several years.

• Diameter reduction: As each log dries, it loses a fraction of its diameter. Over the total height of a wall, this cumulative effect can lead to a settling (sagging) of several inches.

• Consequence for sealing: If the settling is not perfectly uniform, or if the door and window frames are not installed with "sliding boxes" (play spaces), openings are created, allowing air and moisture to pass through.

2. Radial cracks and fissures

As it dries, wood does not shrink evenly. Internal stresses cause longitudinal cracks called splits .

• The path of water: When a crack forms on the upper surface of a log exposed to the elements, it acts like a funnel. Rainwater seeps in by capillary action and can migrate into the house or, worse, stagnate deep within the wood, causing internal rot invisible from the outside.

• Thermal bridges: These cracks also reduce the effective thickness of the wood, creating areas where cold penetrates more easily.

3. The complexity of the joints between the logs

The watertightness of a wall depends entirely on the contact area between two stacked logs.

• Scandinavian fitting vs. caulking: Whether logs are hand-fitted (copying) or machined, there is always a joint. Over time and with freeze-thaw cycles, sealing materials (such as chinking or foam seals) can lose their adhesion or elasticity.

• Wind pressure: During severe storms, the pressure exerted on the facade can push water through the micro-spaces between the logs if the joint is not perfectly watertight and compressed by the weight of the structure.

4. Critical Points: Junctions and Entanglements

The corners of a log house (the intersecting log ends) are the most vulnerable areas.

• End grain: The ends of logs expose the tree's vascular system. This is where water is absorbed most quickly, much like through a straw. If these ends are not treated with specific sealants, moisture penetrates deep into the corner joints, where air circulation is limited, promoting fungal growth.

The weatherproofing of a log house is not a permanent state, but a process of continuous maintenance . Unlike a conventional house where the weatherproofing components are hidden behind the cladding, here they are exposed to the elements.

It is crucial to monitor the condition of the sealant joints (chinking) and the appearance of new cracks each year. A thorough inspection allows for intervention before moisture compromises the structural integrity of the wood.