[Yokohama City] The Importance of Comparing Estimates for Roof Renovation and Key Points to Consider!

1. High Pressure Washing

The entire roof is washed with high pressure. If the dirt is severe, bio-cleaning is recommended.

2. Protection

Areas that may get dirty during roof painting, such as near the exterior walls, are protected.

3. Substrate Adjustment

Repairing cracks in the roof and scraping off old paint and dirt that could not be removed by washing. Rust on metal parts is also scraped off.

4. Rust Prevention for Metal Parts

Rust prevention is applied to metal parts such as sheet metal and snow stops. If this item is missing, rust prevention is often not applied, and there is a high possibility that rust will occur from the metal parts within a few years, so caution is necessary.

5. Primer

There are different types of primers, and it is necessary to choose a primer suitable for the existing roofing material and condition. For example, dedicated primers or undercoats must be used for metal roofs. If the existing roofing material is slate and water-based paint has been applied, using a solvent-based paint without a dedicated primer can cause the paint film to shrink.

To prevent troubles, and to prolong the life of the paint film, it is necessary to use a primer that matches the substrate and condition. Always confirm whether a dedicated primer is used after understanding the condition of the substrate!

6. Installation of Taspacer (Separation Material)

This is a necessary item only for slate roofs. Slate roofs are designed to allow rainwater and moisture to escape from the overlaps of the roofing material.If the overlaps of the roofing material are filled with paint due to roof painting, it will reduce ventilation, leading to substrate corrosion and potentially damaging the roofing material.

Therefore, installing taspacers after the primer ensures gaps in the overlaps of the roofing material. Typically, two taspacers need to be installed for each slate, and the installation positions are predetermined. However, taspacer installation is not possible for roofing materials that are warped by more than 4mm.

7. Intermediate and Top Coating

Basically, roof painting consists of three coats including the primer, intermediate, and top coat. This item is often included by all contractors, but if it is not mentioned, be sure to confirm! There are differences in durability and heat resistance characteristics between the intermediate and top coat paints, so it is recommended to carefully decide which paint best meets your needs rather than just deciding based on price.

+ Replacement of Nailing Board (Check of Ridge Substrate)

This is not related to the roof painting process, but when painting a slate roof that is over 10 years old, we recommend checking the condition of the batten by partially removing the ridge cap. If the existing batten is made of cedar, its durability is estimated to be around 10 to 15 years, so replacing it together can reduce costs compared to doing a batten replacement project separately. Let’s at least get an estimate and consider it!

There are different types of battens, such as “wooden” and “plastic,” and there are differences in durability, so

Make sure to check these points as well!

1. Dismantling existing ridge and snow stops

We will dismantle areas that interfere with the cover method, such as existing ridge caps, battens, and snow stops.

2. Underlayment installation (roofing sheet)

This involves applying a waterproof sheet to the existing roof. This is a key item that should be carefully compared! In conclusion, there are two points to check.

For example, if the main roofing material is Super Galtect (with a durability of about 35 years) and regular asphalt roofing (with a durability of about 10 years) is used, there will be a significant difference in durability between the main roofing material and the roofing sheet. Even if you use a highly durable roofing material, there is a possibility that leaks may occur before the expected durability period, so caution is necessary.

The appropriate roofing sheet for the existing roof depends on the condition of the existing roofing material. For instance, if the existing roofing material is “Colonial NEO” or “Pamil”, which are weak slates, it is important to select adhesive roofing sheets suitable for the overlay method, such as “Tajima Roofing/Tadis Self Cover” (the suitable products may vary depending on the condition of the existing roof and the manufacturer’s installation guidelines). This is why identifying the existing roofing material during the on-site survey is essential!

There are many types of underlayment materials, each with different durability. Since there are various types such as heat-insulating roofing sheets, make sure to check whether the roofing sheet used meets your needs!

Additionally, if there is a lot of moss on the existing roof when using adhesive roofing sheets, the adhesive roofing sheets may not adhere properly. If the dirt is severe, high-pressure washing will be necessary.

Check whether there is a high-pressure washing item included and confirm any additional costs if high-pressure washing is required!

3. Flashing (valley flashing, decorative flashing, eave flashing, waste board flashing, etc.)

There are two points to check regarding flashing!

Using non-genuine flashing may result in differences in durability, and depending on the manufacturer’s warranty conditions, the use of genuine flashing may be required. Some contractors may use aftermarket flashing to reduce costs, so be sure to check this along with the warranty conditions!

The roof overlay method may raise the roof higher than the existing condition, which can cause rainwater to overflow the rain gutter. Depending on the relationship between the existing rain gutter and the roof, using a setback type of decorative flashing can allow rainwater to flow properly into the rain gutter. If you are not replacing the rain gutter, check how the type of decorative flashing and the rain gutter will be integrated!

4. Main roofing installation

This section covers the installation of the roofing material itself! What to check in this section is the “fasteners” for the roofing material! Fasteners can be nails or screws, and they come in different materials such as iron or stainless steel. While stainless steel screws are more expensive, they offer better wind resistance.

If there is no mention of fasteners, confirm what type will be used,

Make sure to check these points thoroughly!

Aijii Industry is the manufacturer of Super Galtect. The repair screws are made of stainless steel and are specifically designed for the roof overlay method. It’s reassuring that they are from the same manufacturer as the roofing material!

5. Snow Stops

Also, check whether genuine manufacturer products are being used for the snow stops! If using aftermarket products, you must confirm compatibility with the roofing material, the manufacturer’s installation guidelines, and warranty conditions, as this could lead to leaks or voided warranties.

6. Ridge Substrate (Nail Board)

The ridge substrate serves as the base for the ridge cap! It is often referred to as a nail board. This is also a critical item to check carefully just like the underlayment! There are various types of ridge substrates, including “wood,” “plastic,” and “metal,” each with different durability lifespans. Generally, we recommend using a ridge substrate that matches the durability lifespan of the new roofing material.

The above photos show wooden and plastic battens. The durability years are just a guideline.

For example, if you use a wooden ridge substrate (estimated durability of about 10-15 years) with a Super Galtect roof material (estimated durability of about 35 years), you will eventually need to replace only the ridge substrate. Since the condition of the ridge substrate cannot be checked from the outside, corrosion may progress unnoticed, leading to issues such as the ridge flashing being blown away. The plastic batten also has an estimated durability of about 20 years, which does not match the durability of Galtect. Thermal deformation and cracking are also disadvantages of plastic battens.

In the case of Super Galtect, if the ridge substrate is made of galvalume steel, the durability will be equivalent, and unlike wood or plastic, it will not crack, making it highly resistant to wind and recommended! Be sure to confirm what material will be used for the ridge substrate!

7. Installation of ridge flashing and rain stop flashing

What you should check here is the “fasteners” and “flashing (sealer)” for the ridge flashing!

First, there are nails and screws with waterproof packing for the fasteners of the ridge cap. If nails are used, they may come loose or have low holding power, leading to the ridge cap detaching. Make sure that the fasteners used are always “screws with waterproof packing.” Additionally, since this area will be exposed to the outside, be sure to check whether the material is “stainless steel.”

A seal is like a packing that prevents rainwater from entering at the ridge. Since it is not visible from the outside, many contractors do not install it. If the item “seal” is not listed, confirm whether it will be installed!

8. Sealing Material

Both the roof overlay (cover method) and re-roofing work require waterproofing with sealing at the rain stop and ridge areas. The necessary confirmation for this item is the type of sealing material. Sealing materials also have a durability period, ranging from about 8 years to 30 years.

If this sealing material deteriorates, it often leads to leaks, so it is best to use high-durability materials! Since the number of sealing locations on the roof is not that large, using high-durability sealing does not result in a significant cost difference, so we recommend using high-durability sealing.

As shown in the table above, there is a significant difference in durability between general sealing materials and high-durability sealing materials!

1. Roof Dismantling

We will strip and dismantle the existing roofing materials such as tiles and slate. The disposal costs for the existing roofing materials vary depending on the type of material and the presence of asbestos. When arranged in order of disposal costs from lowest to highest, they are as follows:

2. Substrate Adjustment

This depends on the condition of the substrate, but if the building is older or if it has a tile roof, there is often “distortion in the substrate.” If the distortion in the substrate is left unaddressed and new roofing materials are installed, the distortion will also affect the new roofing materials, making substrate adjustment necessary.

3. New Substrate Installation (Roof Sheathing)

This involves installing new roof sheathing across the entire roof after dismantling and cleaning the roof. If the existing roofing material is slate or if the building is relatively new, this may not be necessary. However, if the building is older or has a tile roof, it is often required.

The subsequent processes will be the same as steps 2 to 8 of the roof overlay (cover method).

Kanagawa Prefecture

Kawasaki City (Kawasaki-ku / Saiwai-ku / Nakahara-ku / Takatsu-ku / Miyamae-ku / Tama-ku / Asao-ku) / Sagamihara City (Midori-ku / Chuo-ku / Minami-ku) / Yokosuka City / Kamakura City / Fujisawa City / Chigasaki City / Hiratsuka City / Hadano City / Isehara City / Atsugi City / Ebina City / Yamato City / Zama City / Ayase City / Zushi City / Miura City / Odawara City / Minamiashigara City / Aikou-gun Aikawa Town / Kozu-gun Samukawa Town / Nakagun Oiso Town / Nakagun Ninomiya Town / Miura-gun Hayama Town / Ashigarakami-gun (Oi Town / Kaisei Town / Nakai Town / Matsuda Town / Yamakita Town) / Ashigarashimo-gun (Hakone Town / Manazuru Town / Yugawara Town)

Tokyo Metropolis

Chiyoda-ku / Chuo-ku / Minato-ku / Shinjuku-ku / Bunkyo-ku / Taito-ku / Sumida-ku / Koto-ku / Shinagawa-ku / Meguro-ku / Ota-ku / Setagaya-ku / Shibuya-ku / Nakano-ku / Suginami-ku / Toshima-ku / Kita-ku / Arakawa-ku / Itabashi-ku / Nerima-ku / Adachi-ku / Katsushika-ku / Edogawa-ku / Hachioji City / Tachikawa City / Musashino City / Mitaka City / Ome City / Fuchu City / Akishima City / Chofu City / Machida City / Koganei City / Kodaira City / Hino City / Higashimurayama City / Kokubunji City / Kunitachi City / Fussa City / Komae City / Higashiyamato City / Kiyose City / Higashikurume City / Musashimurayama City / Tama City / Inagi City / Hamura City / Akiruno City / Nishitokyo City / Nishitama-gun (Mizuho Town / Hinode Town / Hinohara Village / Okutama Town)

・Parts of Saitama Prefecture, Chiba Prefecture, and Yamanashi Prefecture (please consult us)