Hello! This is Kakeru Koumuten Co., Ltd.!
Today, we would like to introduce roof overlay (cover method) and roofing materials, along with some helpful information to ensure you don’t make mistakes during your first construction project!
Due to a lack of knowledge, some people have been charged high construction fees for roof overlay methods,
or they may have undergone a roof overlay only to find that the underlying structure was rotten, leading to the need for a complete re-roofing in just a few years…
Unfortunately, such troubles seem to occur.
Choosing the right contractor is crucial for construction, so we will also introduce points to consider when selecting a contractor! If you are thinking about your first construction project, we hope you find this information helpful.
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What is the roof overlay (cover method)!
First, the roof overlay method involves laying a roofing sheet (waterproof sheet) over the existing old roof and then placing a new roof on top. This method is also referred to as re-roofing.
Removing all old roofing materials and replacing the underlying structure is known as a re-roofing project.
Next, we will introduce the timing for requesting a roof overlay and the advantages and disadvantages compared to other construction methods.
What are the signs of roof deterioration? Timing to request the overlay method
Some people who request roof work notice visible signs of deterioration, such as stains appearing on the ceiling or noticeable leaks on rainy days.
Indeed, if there are no visible signs of deterioration, it’s easy to think that everything is fine and let time pass.
However, once the signs of deterioration appear, it is too late. The roof overlay (cover method) involves placing a new roof over the existing old roofing material, as explained above. A leak means that rain is infiltrating the interior of the roof on rainy days. Even if a new roof is placed over the old one, the signs of deterioration will not change, and there is a risk that the roof will deteriorate further, leading to a complete roof replacement within 10 years, despite having undergone the roof overlay (cover method).
It is generally recommended to consider the roof overlay (cover method) when the roof is around 20 to 30 years old. Basically, it is advisable to request maintenance once every 10 years, but for new constructions, it is not too late even after 15 to 20 years. Let’s consider maintenance before the roof deterioration becomes irreversible!
There are various types of deterioration symptoms, so let me explain!
Deterioration Symptoms
Roof Lifting and Cracking
One common symptom of roof deterioration is cracking or lifting caused by debris impact.
Slate tiles and cement tiles contain calcium, and the strength differs between new and deteriorated roofs. A deteriorated roof has calcium leaching out due to rain and UV exposure, making it brittle.
In this case, it will generally require a complete roof replacement, but it is important to have a contractor thoroughly assess the roof’s condition and consider whether to proceed with the overlay method or a complete replacement as soon as possible.
Moss and Mold Growth
Moss and mold growth is often seen on roofs. This phenomenon occurs when the roof’s waterproofing function deteriorates due to advancing roof deterioration. If moss and mold are left untreated, the speed of deterioration will increase, and the lifespan will rapidly shorten, so it is advisable to request maintenance from a contractor.
In this case, after removing the moss and mold with high-pressure washing or bio-cleaning, a repainting work will be necessary.
Fading of Roof Color
Fading of the roof color occurs when the paint film peels off due to rain, wind, and UV exposure, causing the pigments in the paint film to wash away. This situation is a good timing for repainting.
However, if this is neglected, the paint film will gradually peel off, leading to leaks, so be cautious.
Rust Formation
Rust formation is commonly seen on metal roofs. This also occurs when the protective function deteriorates due to rain and UV exposure, causing the metal to react with oxygen and water, leading to rust.
If rust is left untreated, it will gradually spread and eventually cause corrosion and holes.
It is more cost-effective to remove rust while it is still small, so consult a contractor early.
Main Types of Roofing Materials
Galvalume Steel
Galvalume steel is a zinc-coated sheet metal made from a composition of zinc, aluminum, and silicon. It excels in heat resistance, durability, and workability, and also offers a wide variety of designs. Compared to conventional metal materials, it is overwhelmingly resistant to rust!
SGL Steel
SGL steel is a galvanized sheet metal that has been improved from Galvalume steel. It is composed of zinc, aluminum, silicon, and magnesium.
Galvalume metal sheets are excellent, but SGL metal sheets have improved the coating, achieving durability that surpasses Galvalume metal sheets.
Asphalt Shingle
An asphalt shingle is a flexible roofing material coated with asphalt on a glass substrate. It offers excellent cost performance while being superior in waterproofing, earthquake resistance, and sound insulation.
Its lightweight nature makes it easy to work with, even on complex roofs. Its flexibility means there are no concerns about cracking or rust.
Recommended Roofing Materials for Overlay Method
Eco Grani
First, we have Eco Grani. It is one of the roofing materials with a long lifespan! The material of Eco Grani is made of zinc-aluminum metal sheets, similar to Galvalume, and is a lightweight metal roof. Its lifespan is about 50 years, and it comes with a 30-year manufacturer warranty.
The surface is coated with natural stone granules, which prevents significant fading and maintains aesthetic appeal over the long term! Additionally, it can reduce summer heat and rain noise.
Diplomat Star
D’s Roofing’s Diplomat Star comes with a 30-year manufacturer warranty. We also provide a 10-year workmanship warranty.
This product is also made of zinc-aluminum metal sheets, similar to Galvalume, and is a lightweight metal roof.
It employs the interlocking method to integrate the roofing materials, allowing it to withstand winds of 60 m/s, as well as excelling in fire resistance and waterproofing.
Yoko Daan Roof
The Yoko Daan Roof is made of SGL metal sheets and comes with a 15-year coating, 20-year rust, and 25-year perforation manufacturer warranty. It is a high-performance insulated metal roof formed by integrating metal sheets (Galvalume coated sheets), insulation (rigid polyurethane foam), and aluminum laminate backing.
It is lightweight and earthquake-resistant, providing excellent insulation performance throughout the year, achieving long-term maintenance due to its high durability.
Super Galtect
Super Galtect is a roofing material that we frequently use. It is also made of SGL metal sheets and comes with a 15-year coating and 25-year perforation manufacturer warranty. Additionally, we provide a 10-year workmanship warranty.
The insulation is applied from edge to edge of the roofing material, and it is a metal sheet that integrates the metal sheet and insulation! The surface is coated with high heat-reflective paint, allowing for a cool summer and warm winter. It also has sound insulation properties, reducing rain noise.
Due to its excellent durability, insulation, sound insulation, and wind resistance, it is one of the most sought-after roofing materials!
Ridgeway
Ridgeway is an asphalt shingle material with a 10-year manufacturer warranty.
Since we use natural stone that is baked onto the surface, this roofing material does not require painting, which helps to reduce maintenance costs. Additionally, because we use fine natural stones on the surface, you won’t have to worry about the sound of rain. Furthermore, the lightweight roofing material is also strong against earthquakes, providing expected seismic resistance.
Points for Choosing a Contractor
When it comes time for construction, one of the challenges is choosing a contractor. This can be especially confusing for those who are doing construction for the first time.
Recently, there have been many cases of poor installation of Galvalume roofing. Currently, only about 10% of contractors are properly installing these roofs.
Not limited to Galvalume, if the roofing installation standards are not strictly followed, issues such as leaks can arise. In such cases, a complete roof replacement may be necessary, leading to additional burdens, so
to avoid regrets, we would like to share some important points to remember!
Check the Website for Achievements and Case Studies
First, check the achievements on the website. Good contractors will have a well-developed website, and those with many construction achievements are more experienced in their work.
Having achievements listed means that they have “nothing to hide and can proudly showcase their accomplishments,” allowing you to request their services with confidence.
While reviews are important, it is not advisable to make a decision based solely on them. First, check the construction achievements and staff blogs on the website.
How to Fill Out the Estimate
Make sure to check that the estimate is not just a rough overview. Good contractors will provide detailed estimates, including unit prices for the materials used.
Contractors who provide detailed estimates can be considered reliable, as there is little worry about overcharging or exorbitant additional fees, allowing you to request their services with peace of mind.
To ensure a satisfactory finish, it is best to avoid contractors who provide extremely vague estimates.
Check for Guarantees and Aftercare Services
It is also important to check whether they offer guarantees and comprehensive aftercare services. Companies that have poor installation practices often do not provide such guarantees.
It is recommended to carefully check aftercare support and warranty periods while making your selection. It’s best to ask about this during the consultation stage.
Roof Overlay (Cover Method) Construction Steps
1. Dismantling the Existing Roof Ridge Flashing
2. Roofing Installation (Waterproof Sheet)
It is made of modified asphalt roofing, which is said to have double the durability of regular asphalt roofing.
As a primary waterproofing measure, if the roofing is solid, there will be no leaks!
We will securely attach it with steel plate chips to prevent it from blowing away.
3. Fabrication of Accessories (Karakusa, Eaves, Valley)
The accessories used are the genuine accessories from Galttect, made of SGL copper plate!
4. Main Construction (Aiji Industrial / Super Galtect)
Once it is installed up to the ridge, we will set up the necessary materials to secure the ridge board called “kanban.” There are types of kanban made from cedar and resin, and this time we used cedar!
5. Ridge Cap Processing & Sealing
We use stainless steel nails and screws that are resistant to rust!
6. Cleaning
This roof overlay (cover method) uses the highly popular Super Galtect from our company. The Galtect used this time features anew color called Shade Wine Red!
You can view other roofing material construction examples⇩here⇩!
Summary
At Kakeru Koumuten Co., Ltd.,
roof rain gutters exterior painting exterior scaffolding setup,
and various other construction works are carried out entirely by our own company.
Therefore, we are confident that our costs, quality, and organization for exterior work are unmatched compared to other companies!
We welcome competitive estimates!
You will be glad you chose us! to ensure that you feel this way,
We are committed to addressing the requests we receive with sincerity.
Our website features many examples of our work, so please take a look!
Helpful information about exterior renovations can be found here!
We look forward to your inquiries. Thank you very much.
・Construction Menu | Roof Overlay (Cover Method) Renovation Costs
・Aoba-ku, Yokohama | Roof Overlay Method | We performed the cover method using Super Galtect!
・Aoba-ku, Yokohama | Roofing Work | We performed a roof replacement using Super Galtect!
・Miyamae-ku, Kawasaki | We performed a roof cover method using Hilanbee 220!
・For those who want to try DIY painting of roofs and exterior walls! Scaffold installation only! Roof and exterior wall painting DIY plan!
・What are the average costs for roof renovations? Types of construction and how to choose a contractor, etc.
・Latest! Grants, subsidies, and reduction systems available for renovations!
・How much does it cost to repair the roof? We introduce the average costs!
・What is the market price for rain gutter repair and cleaning? Tips on timing, fire insurance, and choosing a contractor!!
・Renovation store in Kanagawa Prefecture, Yokohama | What is roof overlay (roof cover method)?
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AAA is a young company with an average age in the early 20s, but our technology is second to none.
One of our greatest strengths is that we can do all of our own scaffolding, roofing, and painting work. In this industry, where work is generally divided, we are able to provide a complete set of services, which saves time and effort in management and reduces costs. Above all, if there is any trouble, we will come to you right away!
We can confidently declare this. We are the youngest and most friendly renovator in Kanagawa!
