What you need to know about galvalume roofs and exterior walls: durability and points to keep in mind.

1-1. Galvalume steel roofs and exterior walls need to be repainted in 15-20 years

One of the characteristics of galvalume steel is its high durability, but this does not mean that it requires no maintenance at all.

Some say it is maintenance-free, but that is not true.

Generally, maintenance such as rust removal and repainting with specialized paints is recommended as early as about 15 years to an average of about 20 years.

This kind of regular maintenance will bring out the true durability of the galvalume steel sheet.

Depending on the type and grade, and with proper rust removal and special coating, the service life is approximately 40 years or more.

If rusting eventually becomes severe or leaks occur, maintenance can be performed by the "cover method," in which a galvalume steel plate is covered over the top in the same manner, or by re-covering.

In the case of general siding exterior walls and roof tiles, it is not possible to put a layer over the top, so the original material must be removed and replaced with a new one, which requires a lot of time and effort.

In the case of galvalume, if maintenance can be performed by simply applying the sheet over the top, the construction cost and time can be reduced.

1-2. Be careful not to let them rust

Here are some points that you should take care of daily to prevent rusting, which is one of the disadvantages of galvalume steel sheets.

First of all, due to the nature of the material, galvalume do not rust with water alone.

However, if sand dust, fallen leaves, etc. are left for a long period of time, they can become charged with static electricity and cause corrosion.

Therefore, we recommend a simple cleaning that washes away dust every few months to a year.

At this time, however, do not use high-pressure washers or deck brushes to wash the surface strongly; use water only to wash away sand and dust on the surface.

The key point to watch out for is "rusting" due to the fact that it is metal.

A shovel that is half rusted or an iron pipe that is half rusted can be left standing, and rust can start to form from there.

Also, because galvalume is a thin metal sheet, it can be deformed by bumping into things, so be careful of such scratches and dents.

Paint will peel away from the scratched or dented areas, causing rust.

Keep in mind that metal is very different from other exterior walls, and there are some points to be aware of that are unique to metal.

2-1. Advantages of galvalume roof and exterior walls

First, here are the advantages of galvalume.

The greatest advantage of galvalume steel is that it is lightweight.

The house is composed of enclosed exterior walls and roof, which is an important element of the house itself and plays a major role in its earthquake resistance.

A light roof and exterior walls require less energy when shaken sideways in an earthquake, and the Building Standard Law also requires more bearing walls and pillars when heavy materials (e.g., Japanese roof tiles) are used for the roof than for a light roof.

Specifically, the "wall mass factor" in the earthquake resistance standard requires a wall mass of 33 (house with heavy roof) and of 29 (house with light roof) on the first floor.

A heavy roof must be supported by approximately 1.1 times as many walls or columns, affecting the availability of the floor plan.

Galvalume (especially the roof) also serve to reduce the overall weight of the house and increase its earthquake resistance, while at the same time easing the constraints of the floor plan.

The second point is a common misconception: because it is metal, its thermal insulation performance is low.

Although not always possible depending on the construction method, both roofs and exterior walls have a ventilation layer behind the exterior wall material and moisture-proof sheets to allow moisture to escape.

Insulation is provided inside that ventilation layer, but insulation calculations do not vary depending on the type of exterior wall.

The reason is that the calculation is done inside the ventilation layer, and is not affected by the type of exterior wall material as long as it is well insulated.

Rather, there are types of galvalume steel plate that are combined with foam insulation on the back, and galvalume steel plate with integrated insulation have better insulation performance than other exterior walls.

It is true that the surface does get hot to the touch in mid-summer, but the same is true of other exterior wall materials and there is no need to worry.

The third point, maintainability, was introduced in "1. Galvalume roofs and exterior walls are highly durable materials," so I will skip it.

川沿いのシルバートール ( architect：Hironobu Hosaka )

The fourth feature of galvalume roofs and exterior walls is their modern design, which is not often designed into other types of exterior walls.

Houses with galvalume can be color coordinated with not only colors such as black and silver, but also blue and red.

It is also attracting attention as a fashionable exterior wall and roof that matches a variety of exteriors, including American style and stylish exteriors.

Depending on the manufacturer and series, there are also siding exterior wall-like type and wood wall-like types for those who see advantages in maintenance, etc. but are concerned about the appearance of metal.

2-2. Disadvantages of galvalume roofs and exterior walls

So far, we have introduced the good points of galvalume steel sheets.

The disadvantages of choosing galvalume roof and exterior walls for new construction or remodeling should also be properly kept in mind.

Here is a list of points of disadvantage.

First point is that there are certain areas that should be avoided depending on the building area. That is salt-affected areas near the coast.

Specifically, if the building is constructed within approximately 1 km from the coast, it will inevitably be affected by salt damage, causing rusting quickly. Although recent products have improved surface treatment technologies such as fluorine treatment, it is still recommended to refrain from using them in salt-affected areas. Colorful American-style houses along the seashore may look nice, but it is safer to use other materials when practicality is considered. Also, place with a lot of sand and dust has a high risk of rusting, so we recommend that you avoid using galvalume.

Second point is the initial cost.

Although it is difficult to make a general statement because it depends on the strengths and weaknesses of each construction company and the prices of its suppliers, prices tend to be higher than those of slate roofs and siding exterior walls, which are the most common type of wooden structures. Slate roofs cost approximately 4,500 yen and up per square meter, while galvalume steel roofs cost approximately 6,000 yen and up per square meter. For exterior walls, siding (ceramic) is approximately 4,000 yen per square meter and up, while galvalume is approximately 5,000 yen per square meter and up, with both roofs and exterior walls being 20-30% more expensive. Of course, this varies depending on the manufacturer, series, etc. If you are concerned about this, please consult with an architect when you consult with us.

Third point, which is the rust generated from scratches, is explained in 1-2. Be careful not to scratch the surface by bumping or standing on it.

The fourth and final point to be considered is design.

Although we have introduced the exterior wall as a perfect example of a modern simple exterior, it can be very monotonous if the overall design and design of the house is not taken into consideration. But it will depends on the design, so if you want a good-looking exterior you should consult with an architect who specializes in design.

3-1. Galvalume steel plate color selection

The choice of color is also important in selecting galvalume.

While most common siding and mortar exterior walls have subdued colors such as white, brown, and gray, galvalume is characterized by colorful choices.

Especially on exterior walls, the colorful and stylish colors unique to metal exterior walls are popular.

Blue (blue to indigo), red (wine red), black, and stainless steel colors unique to galvalume are popular.

Among them, stainless steel color and black colors are steadfastly popular, as they easily match modern-style houses.

In the modern style, blue (blue to indigo) and red (burgundy) colors are used when the style is more westernized, and blue-gray and gray colors are also used in craft styles.

4-1. House in Kobe (Architect: Akiyoshi Nakao)

神戸の家 ( architect：Akiyoshi Nakao )

The house has horizontal, black galvalume exterior walls.

Using steel plates with smart lines in horizontal roofing creates a stylish appearance that looks like a matte steel plate finish.

4-2. House in Asahi-ku (Architect: Akiyoshi Nakao)

旭区の家 ( architect：Akiyoshi Nakao )

This design house has one wall visible from the street side, which is also finished with a black horizontal galvalume wall.

Not a single window is installed, and the entrance is also out-set sliding door for a smart fit.

Unlike its black appearance, the interior has a simple and bright color scheme, with the south facade coordinated with white galvalume.

4-3. Silver Tall by the river (Architect: Hironobu Hosaka)

川沿いのシルバートール ( architect：Hironobu Hosaka )

It is a three-story building with a square design.

The futuristic impression of the galvanized steel sheet wrapped in silver color makes the modern design stand out from the rest.

The entrance door is also clad in galvalume and has a stylish unified design.

4-4. Chofu residence - V-Shaped Courtyard (Architect: Manabu Naya)

調布の住宅　〜V字の中庭〜 ( architect：Manabu Naya )

The building's straight exterior along the road surface gives it a stylish impression.

Galvalume is continuous from the outside of the room and is used for the ceiling.

House in Sorahori (Architect: Akiyoshi Nakao)

空掘の家 ( architect：Akiyoshi Nakao )

This is an example of a 40-year-old used house that was purchased and remodeled.

The black vertical galvalume roof creates the impression that the building is not more than 40 years old, while at the same time providing durability for long-lasting living.

L-Court House (Architect: Noriyuki Tajima)

L-Court House ( architect：Noriyuki Tajima )

This is an example of a house composed in a simple style for both the exterior and interior.

While the silver-colored galvalume steel sheet on the front creates an impressive appearance, the design is not monotonous by incorporating wood grain around the entrance.

4-7. notch house: House incorporating a terrace (Architects: Munenori Matsuo and Haruka Matsuo)

notch house　テラスを取り込んだ家 ( architect：Munenori Matsuo & Haruka Matsuo )

This is an example of the use of black-colored galvalume steel sheet for all exterior walls.

The base colors are unified in wood-tone, black, and white. This modern house combines the simplicity of galvalume with the gentleness of wood.

4-8. Oshima residence (Architect: Yoshihiro Kono)

大島の住宅 ( architect：Yoshihiro Kono )

It is a design house with very large windows and a great sense of openness.

The overall style is natural with a wood base, but accented with black galvalume.

The design is impressive in that the exterior walls are directly connected to the interior walls, and galvalume is also used as accents on the interior walls.

4-9 YADOKARI (Architect: Takanori Ihara)

YADOKARI ( architect：Takanori Ihara )

This is an example of a design house with impressive leaning lines that are not bound by straight vertical and horizontal lines.

Black galvalume exterior walls and roof are used on the front and side to rear elevations from the front road, enhancing the design as a modern residence.

Galvalume is applied diagonally to the rear and sides of the house to create a geometric impression.