What is a Roofing Sheet? An Explanation of Its Role and Types of Roofing!

 

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

Today, we will explain about What is a roofing sheet?

Many people may wonder, “What part is that?” or “What is it used for?” when they hear about roofing sheets. Although it’s not often talked about, it is an important component, and we would like to explain it!

What is a roofing sheet?

First, roofing refers to the waterproof sheet located in the middle part of the roof! Some people also call it underlayment.

Since it is hidden under the roofing material, it is a sheet that you cannot see on a daily basis. You probably won’t see it unless you are building a new house or replacing the roof.

Even if you are interested in roofing materials, most people do not pay attention to the sheet underneath. However, the roofing sheet is a very important building material.

Because it is hidden under the roof, it is difficult to notice deterioration or tears, and by the time you do notice, there is often already a leak or damage.

The necessity of roofing sheets

Roofing sheets are not something you see every day, but they are much more important than the roofing materials themselves. Many people study the effectiveness of roofing materials and carefully consider which ones are best, but few pay attention to the roofing sheet when thinking about their roof.

If the roofing sheet is not properly installed, there is a risk of leaks and corrosion of the sheathing.

It is important to choose a contractor who can ensure high durability and proper installation.

Although it may seem plain and unnoticeable, let’s reaffirm its importance once again.

Main roles of roofing sheets

The role of roofing sheets is, broadly speaking, to protect the roof from rain. Since they are laid under the roofing materials, they are not visible on a daily basis. They serve as a defense line in case the roofing materials allow rainwater to penetrate.

The roof is layered in the following order from the top: roofing materials (secondary waterproofing) → roofing sheet (primary waterproofing) → sheathing (wood).

Especially for tile roofs, there are many gaps to ensure ventilation.
Since there is a high possibility of rainwater entering through these gaps, the roofing sheet for tile roofs is particularly important.

Performance of Roofing Sheets

First of all, as mentioned in the role of roofing sheets, they are laid down for waterproofing the home, so they have excellent waterproofing capabilities.

However, roofing sheets will eventually deteriorate. If your home experiences a leak, it is advisable to request a replacement of the roofing during re-roofing.

If a leak occurs in the roof, unless the building is relatively new, it is generally best to consider re-roofing.

A leak = deterioration of the entire roof is not an unreasonable assumption.

If the entire roof has reached its useful life, partial repairs may not be sufficient, so if there are no plans to move or demolish, a complete re-roofing is the safest option!

Types of Roofing

There are also different types of roofing.

I will explain the durability, cost, and performance in as much detail as possible!

Asphalt Roofing 940

Tajima Roofing/P Color

This is a cost-focused roofing option!

The durability is said to be about 10 years for many of these products.
It is often used in new constructions!

Modified Asphalt Roofing (Rubber Asphalt Roofing)

Nisshin Kogyo/Kappa 23

This is a modified asphalt roofing that we use frequently in our store. The material used is “asphalt.”

Asphalt roofing is a widely used common roofing type, but even within asphalt roofing, there are several varieties.

The material we use is modified asphalt roofing, which is said to have twice the durability of standard asphalt roofing.

This is an asphalt roofing that enhances performance by adding polymers and natural asphalt to standard asphalt roofing.

Modified asphalt roofing offers superior performance in terms of flow resistance, abrasion resistance, peel resistance, adhesion, and deflection tracking compared to regular asphalt roofing.

Breathable Roofing

Tyvek/Roof Liner

This is a high-performance waterproof sheet that has moisture permeability, as indicated by its name. It excels in moisture permeability, durability, and waterproofing, and is a non-woven sheet bonded only by heat and pressure. It has outstanding strength and durability, earning high praise.

It also effectively allows moisture from the sheathing to quickly pass through and be released outdoors, controlling condensation and preventing corrosion and deformation of the sheathing.

When installing, it is necessary to create a ventilation layer, so it must be installed using a ventilation method after setting up the battens and then installing the sheathing; otherwise, the function of the breathable roofing will not be realized!

Tile roofs already have a ventilation layer, making breathable roofing the optimal choice!

Heat-Reflective Roofing

Fukubi/Heat-Reflective Roof Airtex

This is also the ” breathable roofing ” mentioned above, but it has enhanced heat-reflective properties!

Heat-reflective performance is expected to reduce temperatures by 6 to 8℃!

 

Adhesive Roofing

Tajima Roofing/Tadis Self

This is an adhesive roofing that we often use!

Because it adheres to the roof, high waterproofing is expected!
For roofs with a gentle slope (3 sun) or less, the use of adhesive roofing is definitely recommended!

 

In addition to the roofing types introduced above, there are many other varieties available!

How to Install Roofing

Basically, the standard installation method is to overlap and adhere from the bottom up. Rainwater flows from the top of the roof (ridge cap) toward the eaves. To prevent water from entering the interior, the roofing is laid from the eaves to the ridge.

In such cases, it is important to take sufficient overlap, and areas like valleys where water leaks are likely to occur should be overlapped two or three times to enhance resistance against leaks.

Roofing Fixing Methods

Adhesive Type

The adhesive type is characterized by being able to stick directly to the substrate without making holes in the roofing.

It has adhesive tape on one side, and by installing it without using a stapler, it enhances waterproof performance. However, it is necessary to use roofing that is compatible with the adhesive type as a prerequisite, and it tends to be more costly than stapling.

Stapler

This method involves using a stapler (a tool similar to a stapler) to attach the roofing sheet to the substrate. Although it creates holes, there is basically no concern about leaks. The heat from the sun melts part of the roofing, sealing the holes created. Therefore, there is no need to worry about leaks from stapling!

It is limited to cases where the substrate is a wooden frame, so stapling can only be done during re-roofing or new construction!
In the case of the overlay method, stapling is not allowed.

Metal Chip & Nail Fixing

This is the mainstream fixing method for the overlay method. Metal chips are placed at the fixing points and secured with a high-pressure nail gun.

It is strong against wind and can be firmly secured!

This type of construction requires advanced skills, so it is important to choose a reliable contractor.

If the staples are not driven in securely, the roofing may become loose, which could lead to leaks.

About Roofing Installation

Here is a summary of important things to know about roofing installation! Since it is not visible, it is important to pay attention to it, and I hope this serves as a reference for choosing roofing sheets!

Points to Note About Roofing Sheets

Note 1: Check Weather Conditions

The most important thing to pay attention to when building a new house is the weather forecast during the construction period. If the roofing installation is not completed, the wooden frame and other foundational parts of the house will be exposed to rain, causing serious damage.

In case of rain, waterproof measures such as covering with a blue tarp are necessary! Caution is required for contractors who proceed with roofing work even in rainy conditions.

Note 2: Check the Estimate

When replacing roofing sheets, it is recommended not to decide on an estimate from just one company, but to obtain estimates from at least two to three companies.

By getting estimates from two to three companies, you can compare what kind of roofing will be used, compare prices with other companies, and also get an idea of the general cost of roof repairs, so be sure to request estimates from two to three companies, not just one.

Summary

How was that?

Roofing serves as the final line of defense against leaks that cannot be completely prevented by roofing materials alone. I hope you understand the important role that roofing plays among roofing materials.

If you think maintenance is necessary, please contact Kakeru Koumuten Co., Ltd.!

We prioritize our customers and are confident in our work!

At Kakeru Koumuten Co., Ltd., we do not charge until our customers are satisfied after the work is completed!

If you have any concerns after the work, or if you feel unsatisfied for any reason, please feel free to consult us, and we will respond promptly!

Useful information about exterior renovations can be found here!

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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!