野地板とは？屋根下地の重要性について

00:00 Opening 00:10 Today's theme is "Sheathing Boards" 00:23 How to Identify Sheathing Boards and Their Role 01:27 The Difference Between Structural Plywood and Loose Boards 02:43 How to Prolong Sheathing Boards' Lifespan 04:00 What Environment Prolongs Sheathing Boards' Lifespan? Hello, this is Maekawa from Teigaku. Today, I'll be explaining about sheathing boards, an important component supporting a roof. The attic I'm currently in is located at Teigaku's construction base in Ichikawa City, Chiba Prefecture. The first thing you'll notice when you enter the attic is the attic ceiling boards. These are called sheathing boards. A waterproof sheet called roofing is placed on top of these sheathing boards, and then the roofing material is attached to the roofing with nails and screws. Therefore, sheathing boards serve to secure the roofing material. You can also tell if there's a leak by looking for water stains or mold on the sheathing boards. In buildings that are over 30 years old, sheathing boards were often made of long boards about 20cm wide, attached side by side, like this one. Sheathing boards of this shape are called loose boards. There are gaps of about 1cm between each board. These days, structural plywood like this is often attached to sheathing boards. Thicknesses of 12.5mm are often used. Structural plywood has the advantage of improving earthquake resistance and being the same size as tatami mats, so it requires less effort to attach than loose boards, but its lifespan is significantly shorter than that of loose boards. Unlike loose boards, structural plywood sheathing boards are laid out tightly. Sheathing boards with no gaps are more susceptible to condensation due to moisture and are prone to corrosion. On the other hand, loose boards do not corrode across their entire surface, and often only show partial corrosion like this. This building is over 40 years old, but the condition of the loose boards themselves is generally good. If the sheathing is structural plywood, the lifespan of the sheathing is 40 years for colonial or metal roofs. Sheathing begins to deteriorate rapidly between 35 and 40 years after construction. There is a way to extend the life of sheathing. That is attic ventilation. An attic is the space above the roof or ceiling. Many construction experts refer to it as a shanty rather than an attic. This is the place I am standing in. Warm air has a natural tendency to rise higher and higher. And warm air is also humid. For this reason, attics are prone to sauna-like conditions in the middle of summer. If your attic is like a sauna, be careful. Tajima Roofing Co., Ltd. has data showing that when there is a temperature difference between the inside and outside of a humid attic, a temperature difference of just 1 degree can cause condensation, equivalent to one plastic bottle's worth of water, per 1 square meter of sheathing. For example, if a sudden downpour occurs on a hot day, the surface of the roof can cool rapidly, causing the sheathing to become soaked. Some people mistake this for a leak, but this water damage is actually caused by condensation. An environment that extends the life of sheathing is one where the temperature difference between the inside and outside is minimal. In other words, allowing the warm air that accumulates in the attic to escape will extend the life of the sheathing. In the past, when it came to attic ventilation, many homes used either soffit ventilation, which involves drilling holes in the eaves on the underside of the overhanging roof, or gable ventilation, which involves drilling holes in the forehead of the exterior wall of a gable roof. Incidentally, the ventilation component attached to the exterior wall is called a louver. However, these days, attic ventilation is rarely done solely through eaves or gables. These days, attic ventilation almost always relies on ridge ventilation. The ridge is the highest part of the roof. A common ridge ventilation method involves attaching metal sheeting to the ridge area to prevent rain from entering and allow only the warm air in the attic to escape. The metal sheeting used for ridge ventilation is called a ventilation ridge. Since warm air gathers at the highest point, drilling holes there is a very logical idea. Installing a ventilation ridge not only allows a lot of warm air to escape, making the second-floor rooms more comfortable and cozy, but also has the benefit of extending the life of the sheathing. The condition of sheathing is closely related to the lifespan and function of the roof. Sheathing is a very important building component. Be sure to remember its name, its function, and how to make it last longer. ★Subscribe to our channel here! https://www.youtube.com/channel/UCLuh... Teigaku Roof Repair is a sheet metal construction company specializing in roof and exterior wall renovations. If you're considering roof or exterior wall renovations, please feel free to contact us. ...