The Importance of Comparing Estimates for Roof Renovation in Yokohama and Key Points to Consider!

Hello! This is Kakeru Koumuten Co., Ltd.!

We are Kakeru Koumuten, a roofing renovation specialist in Yokohama! On this page, we will explain important points and comparison factors when obtaining estimates for roof renovations!

To conclude, the most important thing in roofing renovation work is
to obtain estimates from at least three companies.

While it is certainly better to have lower costs when obtaining estimates, deciding on a contractor based solely on the estimate costs can also be risky.

Roof renovation work, excluding partial roof repairs, can mainly be divided into the following three types:

・Roof overlay (cover method) work
・Roof replacement work
・Roof painting work

Since the above works involve a complete roof renovation, they typically range from hundreds of thousands to millions of yen.
When it comes to roof overlay or replacement work, it is crucial to thoroughly compare and confirm not only the “main roofing material” but also the “sub-materials” and “processes” to avoid failures.

To ensure that you do not have regrets after the roof renovation work, it is essential to carefully consider the contents of the roofing estimate.
To confidently request a roof renovation, it is important to identify a trustworthy contractor.

To identify a trustworthy contractor, you must obtain estimates from the contractors you are interested in and consider them based on those estimates.

That said, among those who are requesting roof renovation work for the first time,

there are likely many who have such questions.

Therefore, in this article,

How to Decide on Roofing Renovation Work and
Key Points and Important Items for Comparing Estimates for Actual Roofing Renovation Work
will be explained in detail for each roofing renovation project!

7 Points You Should Know When Getting an Estimate

 When getting an estimate for roofing renovation, there are six main points to keep in mind.

We will explain each point in detail!!

1. Always Obtain Multiple Estimates and Compare

As mentioned earlier, the most important thing in roofing renovation work is obtaining multiple estimates.

Obtaining multiple estimates means requesting estimates from several contractors and comparing them.

In Japan, there are many contractors, and even for the same work, the construction methods and materials used can vary significantly.
Therefore, the costs can differ greatly depending on the contractor you choose.

If you decide based on just one estimate, you may not realize you are being charged more than the market rate, even if the request is the same.
By comparing multiple companies, you can understand the appropriate work content and price range.

If you proceed without obtaining multiple estimates,

“There might have been a cheaper contractor out there…”
“I experienced leaks before the promised durability period…”

As such, the likelihood of regret increases, so we at Kakeru Koumuten Co., Ltd. recommend obtaining multiple estimates to all our customers.

Some contractors may extremely dislike providing multiple estimates or may pressure you to sign a contract quickly.
Do not rush into a contract; make sure to get multiple estimates!

2. Check if the contents of the estimate differ too much from other companies

When obtaining multiple estimates, it is also important to check if the contents differ too much from other companies.

It is not uncommon for the construction area to be excessively large or for the price to be too high.
While it is not necessarily bad for there to be significant differences in price or construction details, make sure to confirm with the contractor the clear reasons for any discrepancies.

3. Check if there is a breakdown of materials and other details

When you receive an estimate for roof renovation from a contractor, be sure to check if there is a breakdown included.

Some contractors only list a notation of “one set”, but this does not clarify what and how much money is being spent.

Moreover, this allows the contractor to freely adjust the amounts, increasing the likelihood of inflated costs.

We recommend contractors who provide a detailed breakdown of costs.
Contractors who clearly outline their pricing will give clients more peace of mind when entrusting them with the work.

4. Check if insurance or subsidies can be used

To reduce the costs of roof work, check with the contractor if fire insurance or subsidies can be utilized.

For example, if the roof was damaged due to a typhoon or strong winds, part or all of the repair costs may be covered by fire insurance.
Additionally, roof painting using heat-insulating paint or roof replacement work aimed at improving seismic performance may be eligible for subsidies from local governments.

Using fire insurance or subsidies requires separate procedures.
If the contractor has previously utilized fire insurance or subsidies for past roof work, you can trust them with your project.

Subsidies and Grants Potentially Available for Roof Renovation in Yokohama City

In Yokohama City, there is a possibility of using the following subsidies for leak repairs and roof repairs.
For details, please contact our company or your local government.

Kanagawa Prefecture Existing Housing Energy Conservation Renovation Subsidy

This program aims to promote energy conservation in existing homes, requiring insulation renovations for windows and entrance doors.​In addition, insulation renovations for walls, ceilings, and floors are also eligible for subsidies.​The subsidy amount is up to 200,000 yen, covering one-third of the eligible expenses as a maximum.​Applications must meet certain conditions, such as ensuring the house has seismic performance.

Yokohama City Wooden House Seismic Renovation Promotion Project

Yokohama City provides subsidies for seismic renovation work on wooden houses.​Roof replacement for weight reduction is included in the eligible work, targeting houses deemed insufficient in seismic performance based on seismic diagnosis results.​The subsidy amount is up to 1,000,000 yen for general households and up to 1,400,000 yen for tax-exempt households. 

The availability and details of grants vary by municipality, so please check the official website of your local municipal office or the relevant contact point for the latest information.

5. Is the roof renovation aligned with your life plan?

When considering construction,
it is essential to confirm whether the roof renovation aligns with your life plan and needs.

“I plan to demolish the house or move in 10 years”
“The second floor is hot, and I am considering a roof renovation”
“I am considering a roof renovation due to a leak”

You may be considering a roof renovation due to the above reasons or concerns.

For example, if you have decided to move or demolish in 10 years, using highly durable roofing materials with a lifespan of over 40 years, such as the roof overlay (cover method) or roof replacement work, would be a waste of money.
You need to consider using roofing materials with a lower lifespan and cost, or roof painting as one of the options.
Similarly, if you are considering a roof renovation aimed at improving heat resistance and insulation due to heat, using regular roof painting or low-insulation roofing materials for replacement or overlay will not achieve the original purpose and will result in wasted work.

Additionally, for customers considering roof painting, the most important thing to pay attention to is the “type of roofing material currently used on the building”.
When painting the roof, if the existing roofing material is slate (colonial) roofing, there are roofing materials that cannot be painted, so it is necessary to confirm the type of existing roofing material.
If you paint roofing materials such as “Colonial NEO” or “Pamil” that cannot be painted, it will result in wasted construction costs.

There are many contractors who will casually propose painting work on roofing materials that cannot be painted, so caution is necessary.
For roofing materials that cannot be painted, let’s carry out appropriate roof renovations such as “roof overlay (cover method)” or “roof replacement”!

Click here for more details on roofing materials that cannot be painted!

6. Check the contents of the warranty and after-support

Depending on the construction content, there is a possibility that the work may not go as the customer wishes. It is advisable to choose a contractor that explains warranties and after-support in advance, in case any troubles arise.
When it comes to warranty details, it is important to check not only the warranty period but also how far the coverage extends, such as “leakage warranty” and “detachment of roofing materials and accessories.”

How long is the warranty period? What kind of after-support is available? Let’s confirm these details at the time of the estimate.

When using the overlay method or re-roofing, make sure to obtain a “manufacturer’s warranty.”

7. Confirm that the construction plan is suitable for the location and natural environment of Yokohama City

There are areas within Yokohama City that are subject to strong winds, as well as regions close to the sea, such as Isogo-ku and Kanazawa-ku.
Being close to the sea may result in the “manufacturer’s warranty” not being applicable for certain roofing materials.
In areas with strong winds, it is necessary to ensure that the ridge base and fasteners for the roofing materials are designed to withstand strong winds.
By thoroughly checking not only the cost but also the location of the building and the warranty conditions of the proposed roofing materials, you can minimize the chances of trouble after the construction.

Always confirm whether the plan is suitable for the building’s location and conditions!

【Yokohama City】Roof Renovation Estimation Procedure

We will explain in detail the procedure for requesting an estimate for roof renovation.

Specifically, the process is as follows.

Most contractors will generally provide this service for free, but it is reassuring to confirm whether there will be any costs involved!
Next, we will explain in detail about the estimates when carrying out roofing work.

1. Research Contractors [Check Reviews]

Currently, most contractors have information available on the internet or on signboards, so you can research there.
Additionally, when searching for contractors, it is advisable to obtain multiple estimates and look for several contractors.
By keeping in mind the six points mentioned earlier, the chances of making a mistake will be reduced.

In the case of the internet, there are comparison sites where you can check multiple contractors at the same time, but please be aware that a commission fee will be added to your estimate with a 100% probability.

In other cases, you may see advertisements on public transportation like buses and trains, or receive flyers at your home. If you’re interested, it might be a good idea to contact them once.

That said, narrowing down from the many contractors can be quite challenging.
Therefore, I believe the most reliable method is to read reviews on Google and similar platforms and focus on companies with high ratings when making inquiries.
Google reviews are difficult to delete even if they are negative, making them highly credible!

2. Request an Estimate

To narrow down quality contractors from roof construction estimates, it is important to request estimates from at least three companies.
With only one or two companies, it becomes difficult to compare the details, increasing the likelihood of not finding a quality contractor. By obtaining estimates from three or more companies, you can compare prices, service content, and responsiveness, making it easier to find a contractor that suits you.

Also, when obtaining multiple estimates, make sure to have them created under the same construction conditions.
If you change the conditions, it will be difficult to compare costs and construction details due to too many differences.

3. Have a Site Survey Conducted

Once you have requested an estimate, have the contractor conduct a site survey.
Since the contractor will come to your home, be sure to ask any questions you have regarding the construction at that time.

Examples of questions you may want to ask include:

Additionally, be cautious of companies that provide estimates based only on floor plans or elevation drawings without taking actual measurements of the roof.
Depending on the shape of the roof, it is difficult to accurately determine quantities from floor plans or elevation drawings, and measuring the lengths of ridges and fittings in actual dimensions is indeed more accurate.

Furthermore, by checking the existing roofing materials, you can propose more optimal materials and construction details.

4. Compare Estimates

Once you have received estimates from multiple contractors, please compare each company’s estimate.
The three key points to pay attention to are as follows:

Let’s explain the specific points to be careful about.

1. Check if product names and manufacturer names are listed

Make sure that the details such as the names of paints and materials used in the roofing work, as well as the manufacturer names, are clearly stated.
If there are unclear parts, be sure to confirm them with the contractor.

2. Check if area and unit prices are listed

Always check to ensure that the construction area is not abbreviated as “one set.”
Contractors that provide detailed area measurements are likely to have conducted a more accurate survey and can be trusted.

If the majority of the area in the estimate is listed as “one set,” be cautious.

3. Check if the process and specifications are listed

Also confirm whether detailed processes such as “scaffolding assembly” and “substrate treatment” are included.
If appropriate processes are listed, there should be at least 10 items.

If processes are grouped together as “painting work one set” or “roof work one set,” or if the product names for the battens or roofing sheets in roof overlay or roof replacement work are not specified, it is difficult to understand the details, so caution is necessary.

Comparison Points for Each Roof Renovation Estimate

Finally, we will introduce the essential items to check in the estimates for the three typical types of roof renovation work below!
If the items we are about to explain are not included in the estimate, we recommend confirming with the contractor whether they are part of the work!

① Roof Painting
② Roof Overlay Work
③ Roof Replacement Work

We will explain the essential items to check in the estimates for the three types of roof renovation work!
The installation of temporary scaffolding (including mesh sheets) is a mandatory item for all works, so we will omit it from further discussion!

1. Comparison Points for Roof Painting Estimate Items

First, we will explain the important items in roof painting work in detail by process!

1. High-Pressure Washing

The entire roof will be cleaned with high-pressure washing. 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, will be protected.

3. Substrate Adjustment

Repairs for cracks in the roof and scraping off any old paint or dirt that could not be removed during washing will be done.
Rust on metal parts will also be scraped off.

4. Rust Prevention for Iron Parts

We apply rust prevention to metal parts such as sheet metal and snow guards.
If this item is not included, it is often the case that rust prevention is not applied, so there is a high possibility that rust will occur on the sheet metal within a few years, so caution is required.

5. Primer

There are different types of primers, and it is necessary to choose a primer suitable for the existing roofing material and its condition.
For example, a primer or undercoat is required 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 problems such as the paint film shrinking.
To prevent issues, it is necessary to use a primer that matches the substrate and condition to ensure the longevity of the paint film.

Be sure to understand the condition of the substrate and check if a dedicated primer is being used!

6. Installation of Taspacer (Separation Material)

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

Therefore, by installing taspacers after priming, gaps are secured at the overlaps of the roofing materials.

It is generally necessary to install 2 taspacers for each slate, and the installation positions are also specified.
However, taspacers cannot be installed on roofing materials that are warped more than 4mm.

If the estimate does not include the taspacer item, be sure to confirm the reason!
Also, if the number of “taspacer installations” is not specified, it is necessary to confirm whether the work will be done according to the specified number.

7. Intermediate Coating and Top Coating

Basically, roof painting involves three coats, including the primer, mid-coat, and top-coat.
This item is often included by most contractors, but if it is not mentioned, be sure to confirm!
The mid-coat and top-coat paints have different durability and heat insulation characteristics, so we recommend carefully deciding which paint best meets your needs rather than just choosing based on price.

Rafter Replacement

Although this is not related to the roof painting process, if you are painting a slate roof that is over 10 years old, it is advisable to detach part of the ridge cap to check the condition of the rafters.
If the existing rafters are made of cedar, their durability is about 10 to 15 years, so replacing them together can reduce costs compared to doing a standalone rafter replacement.
Let’s at least get an estimate and consider it!

There are also types of rafters such as “wooden” and “plastic,” which have different durability, so

“What kind of material will be used for the new rafters?”
“Will the ridge cap fasteners be nails or screws?”

Make sure to check these points as well!

In areas close to the sea, such as Kanazawa-ku and Isogo-ku in Yokohama, where the wind is strong, we recommend using a high-wind-resistance “galvalume steel ridge base.”

Here is the price list for Kakeru Koumuten’s roof painting work!

2. Comparison Points for Roof Overlay (Cover Method) Estimate Items Comparison Points

The roof overlay method involves installing new roofing materials over the existing slate roof without dismantling it.
We will explain the important processes and items involved in the roof overlay method!

1. Dismantling Existing Ridge and Snow Stops

We will dismantle the existing ridge cap, rafters, snow stops, and any other areas that may interfere with the cover method.

2. Underlayment Installation (Roofing Sheet)

This item involves applying a waterproof sheet to the existing roof.
This is an item that should be carefully compared!

To conclude, there are two points to check:
“Is the durability of the roof itself balanced with the durability of the roofing sheet?”
“Is the roofing sheet suitable for the existing roof?”
These are the two points!

For example, if the main roofing material is Super Galtect (with a durability of about 35 years) and you use standard asphalt roofing (with a durability of about 10 years), there will be a significant difference in durability between the roofing material and the roofing sheet.
Even if you use high-durability roofing materials, there may be cases where leaks occur before the expected durability period, so caution is necessary.
A suitable roofing sheet for the existing roof means that, for example, if the existing roofing material is “Colonial NEO” or “Pamir”, which are fragile slates, you need to use a self-adhesive roofing sheet specifically designed for the cover method, such as Tajima Roofing/Tadis Self Cover.
Therefore, identifying the existing roofing material during the on-site inspection 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 if the roofing sheet used meets your needs!

Additionally, if you are using a self-adhesive roofing sheet and there is a lot of moss on the existing roof, the self-adhesive roofing sheet may not adhere properly.
If the dirt is severe, it is necessary to perform high-pressure washing.

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

3. Flashing (valley flashing, decorative flashing, eaves flashing, waste flashing, etc.)

There are two points to check regarding flashing!
“Is the manufacturer’s genuine flashing being used?”
“Is the decorative flashing of the setback type being used?”

If genuine flashing from the manufacturer is not used, there may be differences in durability, and in the event of an issue, the manufacturer’s warranty may not apply.
Many contractors use aftermarket flashing to reduce costs, so be sure to check!

The roof overlay (cover method) may cause the roof to be higher than the existing state, which can result in rainwater overflowing the rain gutter.
Therefore, by using setback type ornamental vines, rainwater can be properly directed into the rain gutter.
If you are not replacing the rain gutter, be sure to check whether setback type ornamental vines are being used!

4. Roof Installation

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

For buildings located near the sea or on elevated ground, we recommend using screws for better wind resistance!

If there is no mention of fasteners, confirm what type will be used, and
“Are the fasteners suitable for the needs?”
“What is the additional cost if the fasteners are changed?”
Make sure to check thoroughly!

Aijikogyo is the manufacturer of Super Galtect.
The screws for renovations are made of stainless steel and are specifically designed for the overlay method.
It’s reassuring that they are from the same manufacturer as the roofing materials!

5. Snow Guards

Make sure to check whether genuine manufacturer snow guards are being used!
Using aftermarket snow guards can lead to leaks and may void the warranty, so caution is necessary!

6. Ridge Underlayment (Nail Board)

The ridge underlayment serves as the base for the ridge flashing! It is often referred to as a nail board.
Like the underlayment, this is also a critical item to check carefully!
There are various types of ridge underlayment, including “wood,” “plastic,” and “metal,” each with different durability lifespans.
It is generally recommended to use ridge underlayment that matches the durability lifespan of the new roofing materials.

The above photos show wooden and resin-based purlins.
The durability years of the purlins are as follows.

For example, if you use wooden purlins (durability approximately 10 years) with Super Galtect (durability approximately 35 years) roofing material, you will eventually need to replace only the purlins.
Since the condition of the purlins cannot be checked from the outside, corrosion may progress unnoticed, leading to problems such as the purlin flashing blowing away.
The durability of resin-based purlins is also about 20 years, which does not match the durability of Galtect.
Heat deformation and cracking are also disadvantages of resin-based purlins.

In the case of Super Galtect, if the purlins are made of galvalume steel, their durability will be equivalent, and unlike wood or resin, they will not crack, providing high wind resistance and are highly recommended!

Be sure to check what material will be used for the purlins!

7. Installation of Purlin Flashing and Rain Diverter Flashing

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

First, for the fasteners of the purlin flashing, there are nails and screws with waterproof packing. If nails are used, they may come loose or have low holding power, leading to the purlin flashing coming off, so be sure to check that the fasteners used are “screws with waterproof packing”.
Also, since this will be exposed to the outside, be sure to check whether the material is “stainless steel”!

A face plate is something 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 “face plate” is not listed, let’s confirm whether it will be installed!

8. Sealing Material

Both the roof overlay (cover method) and the roof replacement work require waterproofing with sealing at the rain stop and ridge parts.
The necessary confirmation for this item is the type of sealing material.
Sealing materials have a lifespan, 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, the difference in lifespan between general sealing materials and high-durability sealing materials is significant!

Here is the price list for roof overlay (cover method) work!

Check the Warranty of Roofing Materials

In Yokohama, there are many areas close to the sea, such as Tsurumi-ku and Naka-ku.
Depending on the roofing material, there may be cases where warranties are not provided if you are close to the sea, so be careful when selecting roofing materials!

3. Comparison Points for Roof Replacement Work Estimate Items Comparison Points

Roof replacement work involves dismantling the existing roofing materials and installing a new roof.
The difference from the overlay method is that the existing roof will be dismantled.

1. Roof Dismantling

The existing roofing materials such as tiles and slate will be stripped and dismantled.
The disposal costs of the roofing materials vary depending on the type of existing roofing materials and the presence of asbestos.
Arranging the disposal costs of roofing materials from highest to lowest is as follows:

Low Metal Roof < Slate Roof (No Asbestos) < Tile Roof < Asbestos-containing Roofing Materials High

2. Substrate Adjustment

This depends on the condition of the substrate, but in buildings that are relatively new or have tile roofs, there is often a “distortion in the substrate”.
If the distortion in the substrate is left unaddressed and new roofing materials are installed, the distortion will 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 existing roof.
If the existing roofing material is slate or the building is relatively new, this may not be necessary.
However, if the building is older or has a tile roof, this is often required.
If it is difficult to determine the condition of the substrate during the estimation stage, one option is to check the existing substrate after dismantling the roofing materials to make a judgment.

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

Here is the price list for roof replacement work!

Summary

There are six key points to pay particular attention to when estimating roof renovations.

By referring to the items introduced this time, it will be easier to distinguish between reputable contractors and less reliable ones, so please give it a try!!

Additionally, roof painting, overlay methods, and replacements each have their own advantages, so there may be cases where considering them over a long-term span is more cost-effective. Let’s carefully consider our options.

The important thing is to always obtain multiple estimates and never decide based solely on price!

For roof renovation estimates in Yokohama, contact Kakeru Koumuten

Kakeru Koumuten Co., Ltd. offers free estimates and inspections!
If you have any concerns regarding roofs, rain gutters, exterior walls, or exteriors, please consult Kakeru Koumuten Co., Ltd. in Aoba-ku, Yokohama!

Kakeru Koumuten Co., Ltd. is a remodeling company strong in exterior renovations, and we carry out everything from temporary scaffolding work to roof work and exterior painting completely in-house.
We are confident that in terms of “cost, quality, and organization”, we do not fall behind compared to other companies!

We are confident in our exterior renovations, so we welcome competitive estimates!
We offer comprehensive construction guarantees and aftercare maintenance, and we have received positive feedback for our appropriate proposals that align with cost performance and our customers’ future life plans!

“I’m glad I asked them!” We take every request seriously to ensure you feel this way.

We also have information on roof construction costs and pricing plans for the roof overlay (cover method), so please take a look if you’re interested!

We look forward to your inquiries. Thank you very much.

Service Areas

Since Kakeru Koumuten is based in Aoba-ku, Yokohama, we can serve not only within Yokohama but also almost all areas of Kanagawa Prefecture and Tokyo.

Helpful information about exterior renovations can be found here!

LINE consultations via LINE are also very welcome◎

For roofing, guttering, and exterior work and repairs in Kanagawa, contact Kakerukoumuten Co., Ltd..

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!