How to choose a roofing, where to buy and how to buy [DIY renovation]

08/24/2025

Rate this post

Hello everyone, this is DIY Renova.

The first things that tend to attract attention when renovating the roof are "finishing materials (tiles, metals, slates)" and color, but the lifespan of a roof is "roofing (waterproof thatched material)" that stops rainwater under the finishing material. This article is based on the contents of the uploaded materials, and has integrated the selection logic, material arrangements, quantity calculations, and implementation procedures for Japanese wooden houses (up to 2nd floors) so that even beginners can take action without hesitation.

If you're wondering "How much renovation or remodeling can I actually do on my own home?" or "Where should I even start?", please visit this page. If you're looking to learn more about specific renovation processes or construction details, don't miss this page as well!

So, here you go.

Table of Contents

What you can do in this article

You can choose the roofing that suits your roofing conditions (slope, area, roofing material).
You can see the differences and different uses of the main types (asphalt/modified asphalt/adhesive modification/heat shielding/breathable).
You can calculate the required number of rolls, tape length, and fastener amount on your own based on the roof area.
You can recreate the method of applying non-adhesive and adhesive types in the procedure.
Common mistakes (lack of stacking/winter peeling) can be avoided in advance.
You can find out the tips for buying cheaply and wisely with EC (shipping lines, coupon use, lot checks).

Safety and legal premises (Japan)

For work at a height of 2m or more, a "fall prevention device (full harness) + master rope" is required (compliant with occupational safety and health regulations). Even in DIY, please follow safety standards and cure.
Take into consideration the neighborhood and take into consideration work time, noise and dust.
If electricity, gas, or solar equipment is involved, inspection and connections are required by a qualified person.

"Safety equipment" is just as important as construction quality. Make sure to prepare full harnesses, lanyards and non-slip roof shoes first.

[Self-Renovation] If You Want To Install Scaffolds, You Should Prepare Together [Diy Renovation]

リンク

Roofing Basics (role, terminology, expected durability)

The role is to "reliably stop water that has passed through the primary waterproofing (roofing material) with secondary waterproofing, preventing rot and condensation problems of the field board."
Overview of representative types
- Asphalt roofing: long history and low prices. Practical for renewal cycles of around 10 to 15 years.
- Modified asphalt: Rubber and resin for enhanced heat resistance and durability. Practical standards.
- Adhesive Modification: Self-adhesive throughout the circumference, with no nail holes. While it is resistant to slow slopes and strong winds, it cannot be re-sticked.
- Heat-shielding modification: Solar reflection by aluminum vapor deposition, etc. Prevents rising field temperatures in the summer.

リンク

The standard guideline for "layer dimensions" is 100mm horizontally stacked and 200mm vertically stacked, and the valleys, eaves, buildings, and through parts will be added to the pasted portions (concretely described in the procedure described below). These numbers are in line with the construction concept of the entire document.

5 steps to select without fail (shortest logic)

STEP 1 Roof material and slope

Metal roofs (SGL/galvalume) are prone to high temperatures in the summer, so a ``heat resistance of 80℃ or higher'' is a must.
If the slope is less than 3 inches (approximately 16.7%), we recommend "adhesive type" or "modified No. 2 + double-layered waterproof tape."

STEP 2 Climate classification and environmental risks

Okinawa/Minami Kyushu: "High temperature and humidity + typhoon" → Heat shielding + adhesive.
Heavy snow in Hokkaido: "Water and ice" → 1.0mm thick modified No. 2 or more.
Tokai, Tokyo area: "All year-round rainfall + high summer temperature" → Modified No. 2 + heat shielding.

STEP3 Expected useful life

If you want to renew the entire roof in 10-15 years, "Asphalt 1" is enough.
If you're aiming for a long-term 30-year class, try higher grades such as "Modified No. 2," "heat shielding," and "adhesive."

STEP 4 Installation method and DIY possible

Beginners: The basic method is "Modified No. 2 (non-adhesive)" that can be re-sticked and easy to handle.
Skilled: The "adhesive type" with zero nail holes and the strongest water stopper. However, re-sticking is not possible.

STEP 5 Budget and cost-effectiveness

Even if the price difference between sqm is several hundred yen, there are many cases where high-performance products are cheaper at running costs in 30 years.

リンク

Use of main types (quick reference table)

"Slow slopes, strong winds, lots of penetration, and want to suppress working noise" → Adhesive types are advantageous (integrated with the base and are less likely to flow backwards. Cannot be re-applied, adhesive decreases at below 5°C, price is 1.2 to 1.5 times).
"General gables, sufficient slopes, and cost emphasis" → Non-sticky is enough.
"I want to lower the attic temperature in the summer" → Select heat-shielding reform.
"Short-term operation assuming updates" → Asphalt No. 1.

Practical scenario by slope/region (quantitative example)

Kanto/5 inch gradient/SGL steel plate 100 m2: "Modified No. 2 + heat shielding". Material costs vary by several hundred yen per m2, and top-class products are advantageous for long-term running.
Hokkaido / 2.5 inches / Asphalt single: "Adhesive modified 1.0mm + Tani double layer". Because of the long running time.
Okinawa / 1.5 dimensions uneven / Folded plate cover: "Adhesive heat shield directly applied → cover with new metal". Provides both typhoon and high temperature countermeasures.

Quantity calculation (formula that anyone can calculate)

Roof area A (m2)=Fractional projected area of the building x gradient correction.
If the slope is n dimensions (n/10), the correction factor = √(1+(n/10)²). Example: 5 sun → √(1+0.5²)≒1.118.
Effective coverage area of 1 roll S
Assuming that the standard width is 1.0m x length is 18m, the effective width is 0.9m for 100mm horizontal stacking, and the effective length is 17.8m for 200mm vertical stacking.
Therefore, S≒0.9 x 17.8 = 16.0 m2 (approximate).
Number of books N=Runs up A/16.0 + 1 spare.
Example: A=100㎡ → 100/16=6.25 → 7 bottles + 8 bottles in total, including spare.
Tape Primer
The joint tape (50mm wide) is the number of vertical joints x 1.2m (including room to spare) plus the extra valleys and eaves.
The adhesive type primer is 0.1 to 0.2L/m2 (according to manufacturer specifications).
Fastening
If it is not adhesive, use a tacker or washer nail to 300-400mm pitch (additional winds to tighten the area).

Preparation (weather, base, tools)

Weather: Avoid rain forecasts, wind speeds above 8m/s, and temperatures below 5°C. Adhesive materials lose their adhesive at low temperatures, so in winter, use a heat gun to warm the base.
The basic moisture content of the base: The base plate is "less than 20%." Thoroughly remove dust, oil and moisture.
Must-have tools
- Moisture content meter (pin type)
- Chalk Line
- air release roller
- Heat gun (temperature control possible)
- tacker or washer nail
- Butyl-based joint tape
- Modified silicon seal
- Full harness + parent rope

リンク

Complete guide to "optimal roofing" and "heat insulation and insulation panels" that change depending on the roof material (Japanese version)

Introduction

If the roof finishing materials (tiles, galvanized steel sheets, slate, asphalt singles, etc.) change, the best roofing (waterproof thatched material) and the heat-insulating and insulation panels that should be used will change. The reason is simple: each roofing material has a different way of receiving heat, how rainwater flows, and how easily condensation occurs. Furthermore, Japan has long been in north and south, with the climate being different, with high temperatures and humidity in Okinawa, heavy snowfall in Hokkaido, and typhoons on the Pacific side. If you say "cheap roofing is OK for the time being," you will be prone to tears by the later leaks, scorching summer heat, and winter condensation.

In this article, we will explain how to choose a roofing and the combination of heat insulation and insulation panels, in a systematic way, for beginners to practice without hesitation.

First, the overall picture: compatibility between roofing and under roofing materials

Metal roof (galvanized SGL steel sheet): The surface temperature in summer is likely to reach 80-90°C, and the field base plates and insulation materials are likely to overheat. "Heat insulation" and "High heat resistance" are given high priority.
Tiles (ceramic tiles/disaster prevention tiles): The roofing material itself is thick and has a structure that allows for easy ventilation. A balance between "durability" and "nail hole sealing" is important. Heat shielding is a high priority.
Slate: While lightweight and easy to apply, it also easily accumulates heat on the roof. It benefits from "modified asphalt" and "heat shielding".
Asphalt single: It is often used for gentle slopes to ensure water stopping by "adhesive" or "double pasting".
Folded plate roof (warehouse/factory/cover method): Large area with large wind pressure and heat load. ``Adhesive + heat shielding'' and ``outer insulation panels'' go well together.

(Engineering supplement: The heat on the roof moves through "radiation", "convection" and "convection". Metal roofs are easy to absorb radiant heat, and heat is transferred through conduction to the field plates, so it is effective to design that reflects radiation with the heat shielding layer and allows heat to escape through convection with the ventilation layer.)

Decisions made in 5 minutes (for initial meetings)

What is the roofing material?
- Metal (ridden, horizontal roofing, metal tiles) / tiles / slate / asphalt single / folded board
What is the roof slope?
- If it is less than 3 inches (gentle slope), use "adhesive" or "double pasting".
Is there a ventilation layer?
- If air flows up and down through the rim or ventilation rafters, a "breathable" system is also an option.
What is the local climate?
- The priority functions change due to constant typhoon attacks, heavy snowfall, and high temperatures and humidity.
What is your target life expectancy and budget?
- If it's 10-15 years, it's possible to use a 1-size asphalt. If you're looking for 30 years, you can use reformed No. 2 or higher + heat shielding and adhesive if necessary.

Under roof and panels that fit galvanized steel sheets (siding flat roof and horizontal roof)

Vertical roofing (assuming straight roofing, no girth)

Recommended roofing: Equivalent to "heat shielding" + "modified asphalt No. 2". The thickness is approximately 1.0mm.
Reason: Because you need to prepare for both condensation and high temperatures on the back of the metal roof. Products with high nail hole sealing properties are safe.
Prone to NG: Use a "breathable system" even though there is no ventilation layer. There is no way for water vapor to escape, and on the other hand, there is a risk that moisture will accumulate.
Even more safe: "Tani", "Elephant", and "Building" are double-layered, or added to the joint with butyl tape.

Thatched roof (with slats and local ventilation)

Recommended roofing: Heat-shielding modified asphalt (1.0mm).
Conditionally: The gaps are removed by the bar, so the partial benefits of breathable system are also available. However, it is not completely ventilated so I don't overconfident.

Use of heat insulation and insulation panels together

Heat shielding panel (reflective sheet integrated base): Reflects radiant heat from the roof surface. A vent layer is more effective.
Exterior insulation (phenol foam, hard urethane, etc.): Used when you want to strengthen roof insulation. Construction costs increase, but the interior is highly comfortable.

(Engineering supplement: Heat shielding is a technique that reflects infrared rays to bounce back energy before it reaches heat conduction. Even if it drops a few degrees Celsius, it has the effect of suppressing the rate of adhesive degradation in plywood.)

Tile roof (ceramic tiles, disaster prevention tiles, Japanese tiles)

Recommended roofing: Based on modified asphalt No. 2 (1.0mm), we place emphasis on the "nail hole sealing performance" of the stacked parts.
Heat insulation priority: Medium. The tiles themselves are thick, making it difficult for direct sunlight to reach the ground, but using heat shielding in conjunction with the ground to reduce the ground temperature will contribute to a longer lifespan.
Consideration of breathable systems: It would be effective if there are tile bars and ventilation layers. However, if the ventilation path is blocked halfway, the effect will be reduced.
Double pasting has been made into a habit of stopping snow and valley gutters.

Slate (makeup slate)

Recommended roofing: "Heat-shielding Modified No. 2" or "Roof material made with Modified No. 2 + heat-shielding paint."
Reason: Slate is thin and easy to heat through, and the attic temperature tends to rise. It has a great effect of heat shielding to prevent room temperature rise in summer.
If the slope is gentle, the "adhesive type" is the priority.

Asphalt shingles (common on gentle slopes)

Recommended roofing: "Full-surface adhesive type" or "Modified No. 2 + adhesive tape."
Reason: Singles can be used even if they are less than 3 inches, and there is a high risk of refluxing through the nail hole. It's safe to use when you install adhesion and zero nail holes.
It is desirable to have heat insulation, but first, water stopping is your top priority.

Folded board roof/cover construction method (covered over warehouses, factories, and existing roofs)

Recommended: High-performance adhesive + heat shielding type roofing (as the base is metal and nails are difficult to work).
Furthermore: Configuring roof insulation with exterior insulation panels (PIR, phenol, etc.) greatly improves air conditioning efficiency in summer and winter.
Installation note: Rust and dirt removal from existing roofs and primer treatment. Cleaning the base is the key to sticking.

Metal tiles and steel plates with stone grains

Recommended roofing: Based on Modified No. 2, it is effective to use heat-shielding in hot areas.
Reason: Although it is a metal base material, it is a stone grain layer that reduces direct impact, so heat shielding is one level lower than the straight roof of the metal plate. However, the temperature in the attic will rise, so if you are looking for comfort, add heat shielding.

Flat roof/super gentle slope (less than 2.0 sun)

Recommended: Rather than roofing, it is the design area for "waterproofing layers (modified asphalt waterproofing, PVC sheet waterproofing, urethane coating waterproofing). Follow the specifications of a professional waterproofing company.
Even if undercover roofing is required, rules are strict, such as adhesive, large layer width, and triple waterproofing around the drain.

The evaluation of "breathable roofing" changes dramatically depending on whether or not there is a ventilation layer.

With ventilation layer: Breathable roofing is a life. Water vapor inside the roof can pass through and be released through ridge ventilation and eave ventilation.
No ventilation layer: In principle, we do not recommend breathable roofing. Because there is no escape for water vapor and there is a risk of condensation in the layer.

(Engineering supplement: Condensation is a phenomenon in which water vapor in the air becomes liquefied when it cools below the dew point temperature. The back of the metal is easily quenched by radiant cooling, and if there is no ventilation, water vapor is likely to stay in place and condensation is likely.)

Summary of key points for roofing for resin roofs (polycarbonate, PVC, FRP)

The resin roof is characterized by its "lighting, lightweight, and high expansion." Here we will focus on the "roofing perspective" and summarize only the minimum and no hesitation in mind.

Firstly, assumptions (thrust-stimulating important)

Like carports and terraces, ``the bottom is outdoors and there are no roof boards,'' → roofing is usually not installed.
Consider roofing as a secondary waterproofing option only when creating a plywood base and using corrugated resin sheets or hollow sheets as roofing material.

Deciding whether to use or not

Breathable roofing: It is generally not used on plastic roofs that do not have a ventilation layer. Consider only if ventilation paths are available.
Modified asphalt (approx. 1.0mm): First general-purpose candidate. Highly heat resistant and suitable for protecting field floor boards. Double-layered coating is recommended for gentle slopes.
Adhesive type: Advantageous with gentle slopes, strong winds, and covering methods. If you choose "non-bleed adhesive", you will not be able to cause stickiness or transition problems even if the other party is plastic.
Polymer (PO-based) Non-asphalt: Effective when there is a possibility of contact with PVC (PVC). There is little concern about the transfer of plasticizers, and the compatibility is safe. This is good for environments that can only be applied when deliberately creating layers that allow rain to pass through, like resin roofs! (Roof Ramitect, etc.)

Points that are only effective when using a plastic roof

Adhesive roofing, which has been labelled "Directly attached to PVC", "Non-bleed", and "No plasticizer transfer", is designed to be compatible with resin bases and resin finishes. Be sure to check the manufacturer's specifications for "Compatible base: PVC, FRP, etc.".
Although resin roofs benefit less from heat insulation than metals, it is worth using heat insulation reforms to "prevent thermal deterioration of field surface plates."

Notes on the details (short and core)

PVC and asphalt may transfer plasticizers. It's safe to sandwich an insulating film about 0.1mm polyethylene in between.
Insurance is provided with double-layered adhesion + butyl tape for valleys, eaves, and walls.
Translucent roofing materials tend to get hot. If you want to cool your indoors, we prioritize "heat shielding panels + ventilation" over roofing.

Approximate selection flow (30 seconds)

No ventilation layer → "Modified AS 1.0mm" or "Non-bleed adhesive."
There is a ventilation layer → "Breathable system" is also a candidate. However, if the slope is small, sticky is the priority.
The roofing material is PVC (PVC) → "PO-based (non-ass)" or "non-bleed adhesive" + insulated film if necessary.

A summary

The purpose is "secondary waterproofing". With plastic roofs, the roofing material itself is primary waterproofing, so roofing is water stop insurance and field protection. Don't forget to match (plasticizer/adhesive bleed).

Thickness guide and durability

How to use	Thickness guide	comment
General housing, slope of 3 inches or more	Approximately 1.0mm (equivalent to modified No. 2)	Good balance between construction and durability
Slow slopes, heavy snow and water stagnation are a concern	Approximately 1.2mm	Use it in conjunction with double-layered adhesive and adhesive to increase your peace of mind
Large area and factory	1.5mm or more	Costs increase but durability is important

It's not necessarily better to be thicker. The thicker it becomes, the heavier and harder, making it difficult to handle with DIY, and the folding of the layered parts tends to become wrinkled. Make sure you know what is necessary and well.

Choosing adhesive and tacker types

Adhesive type: No nail holes for the best water stop. It is advantageous for gentle slopes, typhoon areas, and covering methods. It is sensitive to base cleaning and temperature conditions, and cannot be re-sticked.
Tucker type: Can be redoed and easy to choose the materials. Use tape on the stacked portions together and double-layered surfaces to increase the water stopping properties.

(Practical points: In winter, adhesive strength tends to decrease, so avoid installation at temperatures below 5°C or warm up the base. In summer, adhesiveness is too strong and positioning is difficult, so it is safe for two or more people to work.

Basic knowledge and how to choose heat insulation and insulation panels

Heat shielding panel (integrated reflective sheet)

Role: Reflects radiant heat and suppresses heating of roof boards and insulation materials.
Compatibility: When combined with a ventilation layer, the effect will be improved. Direct fitting is limited, but it can still be expected to reduce the temperature by a few degrees Celsius.

External insulation panel (PIR/phenol/EPS/XPS)

Role: Cuts conduction heat and stabilizes the thermal environment inside the room (contributes to improving performance ratings such as insulation).
Note: As the roof structure fits differently, it is essential to consider fire-resistant and wind-resistant designs and fixing methods. Although the cost is high, it also reduces heating and cooling costs.

(Engineering supplement: The performance of insulation is evaluated based on the thermal conductivity λ (Watts/Meters/Kelvin). The smaller the λ, the higher the insulation performance, and for phenol foam and PIR, the smaller the λ, the higher the performance.)

Tuning by Climate (Japan)

Areas with a lot of typhoons: adhesive type + large layer width. Tape is added to the eaves and edges of the building.
Areas of heavy snow: Due to the longer period of water retention, thickness of 1.0mm or more + double-layered. Be especially careful when blocking snow.
High temperature and humidity: Great benefits from heat insulation. If the ventilation layer cannot be removed, a heat shielding layer is the priority.

Practice: Recommended configuration examples for each roofing material (cross-sectional image)

Example 1: Galvanized Ripe (no ventilation layer)

Finish: Galvanized Rippei
Under roof: heat-shielding modified asphalt (approx. 1.0mm)
Field board: Structural plywood 12mm
Insulation: Ceiling insulation (glass wool 16K 100mm, etc.)
Ventilation: Elephant ventilation/attooth ventilation fan (optional)

Example 2: Tile roof (with ventilation layer)

Finishing: Ceramic tiles + tile tiles
Under roof: Breathable waterproof roofing (for ventilation roofs only)
Ventilation: Ventilation between rafters → Exhaust through ridge ventilation
Insulation: ceiling insulation + airflow stop

Example 3: Cover method (metal horizontal roofing over existing slate)

Existing: Slate
Under roof: Adhesive + heat shielding roofing (stick directly on existing surfaces)
Finish: Metal horizontal roof
Note: Cleaning existing surfaces, flattening the base, and water stopping details at the edges

Construction procedure (general example of tucker type)

Base check: Check the floating, moisture content, and nails on the field plate. The moisture content is below 20% as a guideline.
Cleaning: Removes dust and wood debris. If you want to attach the eaves first, place them out.
Laying: From the eaves towards the building. Temporary fastening while eliminating wrinkles → genuine fastening. The basics are 100mm horizontally stacked and 200mm vertically stacked.
Joint treatment: Add more stacked parts, penetration parts, and valley parts with butyl tape.
Edge treatment: Double pasting at valleys, ridges, and walls. If you plan the layout in advance, the result will be beautiful.

Installation procedure (general example of adhesive type)

Drying base: Wet, dust, and oils are strictly prohibited. Apply primers if necessary.
Alignment: Draw a reference line with a choke line.
Attachment: Peel off the backing paper little by little, and press it while ejecting the air. Fully pressed with rollers.
Penetration part: Add extras of the pipes and hardware area beforehand, then press down with the original paste.
Measures when at low temperatures: Avoid installation if the temperature is below 5°C, or warm the base before crimping.

Common Failures And Countermeasures

Lack of overlapping width: "100cm wide and 200cm long" is enough to protect. The valley is double-layered and tape.
Misuse of moisture permeable systems: Using moisture permeable systems without a ventilation layer, resulting in condensation within the layer. Think in conjunction with ventilation design.
Disregarding nail hole stickers: Rainwater flows backwards in slow and strong wind areas. Switch to adhesive types or high-sealing products.
Defective adhesive in winter: peeling off when applied at low temperature. Avoid by curing, heating, and seasonal selection.

Estimate and Order Checklist (Archived Edition)

Target life expectancy (10 years/30 years/40 years)
Roofing materials (galva, tiles, slate, single, folded board)
Slope (○ size) and area (○㎡)
Ventilation plan and presence of ventilation layers
Types of roofing (Modified No. 2, heat shielding, adhesive, moisture permeation)
Layered width and double pasted area (valley, building, eaves)
Attachments (tape, primer, roller, tucker)

Purchasing tips and easy guidance (store usage)

Bulk purchases reduce shipping costs. If you pack it with joint tape, nails, and tacker needles, it will easily reach the "Free Shipping Line."
Examples of search keywords: "Modified asphalt roofing 1.0mm", "Heat shielding roofing reformation", "Adhesive roofing 20m".
Reasonable standard items can be found on each e-commerce. For example, it is convenient to find the following:
- [Search for roofing on Amazon] (assuming that you will be plugging in affiliate links)
- [Search for roofing on Yahoo! Shopping] (assuming that affiliate links will be inserted)
- [Search for roofing on Rakuten Market] (assuming that affiliate links will be inserted)

*Please add your own affiliate ID to the actual link. Searching by product name or JAN code will reduce erroneous orders.

Legal and Safety (minimum in Japan)

Building Standards Act: The waterproof and fireproof performance of the roof must meet the specified specifications.
Fireproof areas and semi-fireproof areas: There may be restrictions on the combination of roofing materials, basements, and insulation materials. Check local government guidelines in advance.
Occupational Safety and Health Act: Measures to prevent falls and falls (primary rope, safety belt, scaffolding) are essential for work at a height of 2m or more. Even if you are DIY, you cannot be at your own risk.
Industrial waste disposal: Used roofing is properly treated with waste plastic, fiber waste, mixed waste, etc. Even if heat-shielding aluminum deposition is used, it can usually be treated as industrial waste. Check in advance whether small amounts are accepted.

Q&A (Frequently Asked Questions)

Q. Can I use a breathable roofing with a vertical roof?

A. We do not recommend this unless there is a ventilation layer such as a body edge. There is no escape for water vapor, increasing the risk of condensation. It's effective if there is ventilation.

Q. Is 1.0mm thick enough?

A. A sloped roof in a regular home is sufficient. For slow slopes or heavy snowfall, consider applying 1.2mm equivalent or double-layered paste.

Q. Which is safer, adhesive or tacker?

A. The waterproofness is high adhesive. Tucker is more convenient to start over. Choose by slope, region, and budget.

Q. Which works better, heat-shielding panels or heat-shielding roofing?

A. If a ventilation layer can be ensured, the synergistic effect of heat shielding panels (reflective + ventilation) will be great. If there is no ventilation, heat-shielding roofing is more realistic.

Installation procedure (Non-adhesive type: Modified No. 2 as an example)

It is ideal for DIY purposes as it is "re-sticking and easy to handle." Below is the standard procedure.

"Demolition and removal"
Remove the ridge wrap → drain the burial drain → rain cover → eaves arabesque → roof material itself. In principle, valley sheet metal is exchanged. Raise the nails and then pull them straight out.
"Standard maintenance"
Repairs rot and looseness of the base plate. If necessary, adjust the surface with an extra plywood and use a blower and brush to remove dust. Check that the moisture content is below 20%.
"Basic Line"
Chalks are pulled parallel to the eaves, and all stages are equipped with 100mm horizontal lines. The vertical joints are arranged alternately on the top and bottom stages.
"First level (below)"
Place a roofing 10-20mm of the new eaves arabesque, and hold the tacker or washer nailed at a 300-400mm pitch while allowing air to escape from the center to the outside.
"Second row and beyond"
Always from the bottom to the top. Strictly adhere to the horizontal overlap of 100mm. Be sure to make the vertical seams with the water side facing up.
"Tanibe"
First, "discarding and pasting" straddle the valley center, doubled with a 300mm width (one side) → Insert the main paste from the left and right sides, and add more with joint tape. The documents also recommend that you add more valleys.
"Wind/Keraba"
The building is stacked 200-300mm across the core. The edge of the kerabas is expected to cause wind to enter, and the final layer is pasted to ensure that there is no floating.
"Piercing part"
The ventilation cylinder, pipes, and top lights are expanded to 100-150mm above the start, joint tape, and special sheet metal, and create a water channel.
"Finishing Inspection"
Check for zero exposed nails, vertical joint orientation, double valleys and eaves, and no floating at the edges.
"Roof material genuine roofing"
Even in modified systems, long-term exposure is risk of edge breakage. Complete the roofing in 3 months.

Installation procedure (adhesive type: self-adhesive throughout)

The advantages are "zero nail holes" and "resistant to gentle slopes." Since it cannot be re-pasted, the base and preparation are the key.

"Cleaning and drying"
Dust, oil, and moisture are not allowed. Check that the moisture content is below 20%.
"Primer"
Genuine manufacturer coating is applied all over. Approximately 0.1 to 0.2L/m2. Installation after drying.
"Expanding"
Peel out the release paper little by little from the edge and allow air to escape from the center.
"Crimping"
Strong pressure with air vent rollers. Carefully cascade, edges and valleys. If the temperature is below 5°C, warm the base to a level of human skin.
"Layout"
The basics are 100mm wide and 200mm long. Added additional pasting to roofs with gentle slopes and strong blow-ups.
"Finishment inspection"
Visually visible and touched, it does not float. In winter, re-inspect the next day and if there is peeling, it will be re-inspected and crimped.

You can make faster decisions by sorting out the conditions for adhesiveness (slow slope, emphasis on rain shutdowns, avoiding the risk of nail holes) and points to note (cannot be re-applied, lowered adhesion at below 5°C, and slightly higher prices).

Cover construction method and partial repair (criteria)

The cover construction method, which "layers new roofs over existing roofs," has the advantage of shortening construction periods and reducing waste materials, which eliminates the removal of existing roofs. If you apply adhesive heat shielding directly to the under roof, then a new metal roofing will increase the negative pressure and reduce heat in the summer (effective in areas where typhoons are constantly hit in Okinawa and southern Kyushu).
If local deterioration (valleys, eaves, and penetrations) are clearly visible, it can be extended by using partial repairs and double-layering. However, if there is fundamental deterioration (rot and high water content of the field) it is prioritized to fully renew the area.

Quality checklist (you can do it yourself)

Actual measurements of 100mm horizontally and 200mm vertically are observed at all locations.
It contains additional pastes (approximately 300mm grade) for the valleys, eaves, and buildings.
The vertical joints are staggered at the top and bottom steps, and the water is "top above."
No exposed nails (butyl + seal on unavoidable areas require double water stop).
No float, wrinkles, or curls. The adhesive has roller marks.
Ensure a hanging dimension of 10 to 20 mm for the eaves arabesque.
100-150mm rise at the penetration part + discarded sheet metal.
Take and store the completed photos.
These are the practical steps that have been used to denote the Q&A, failure cases, and recommended maintenance intervals in the documents.

Common failures and countermeasures (examples)

"Reverse flow due to lack of side-layering"
Symptoms: Water leakage from the building.
Cause: Only 50mm of horizontal stacking was removed and the wind and rain caused a backflow.
Countermeasure: Corrective measures to 100mm wide and add more joint tape.
"Adhesive peeling in winter"
Symptoms: Applying it to float after 3 days.
Cause: Temperature is 0°C and wet under the base.
Countermeasures: Thorough warming, primer application, and roller crimping.
"Re-sticking"
Adhesive types are generally "unrepairable." Reduce the chances of failure by taking dimensions, temporary attachments, and two people installations.

How to purchase and cost reduction (EC)

E-commerce specializing in building materials (e.g. MonotaRO PRO, Aunworks, etc.) has a wide selection of "reformed No. 2 or higher." Use the price comparison service to cross the same JAN and compare the total amount of the unit and shipping costs.
The coupon rate is likely to increase during "financial month and before long holidays" (aiming at a maximum of 15%). However, recently the prices of materials themselves have risen significantly, so on the other hand, it might be a good idea to buy them early and buy them before the price increases.
The trick is to include joint tape and nails from the same manufacturer to cross the free shipping line.
Don't forget to check the "manufacturing lot and storage status." Long-term inventory of adhesive products has a risk of lowering adhesiveness, so check the manufacturing date.
Other consumables (rollers, heat guns, moisture content meters, choke lines, full harnesses, etc.) are easy to buy in bulk when price fluctuations are small.

Q&A (Simply put the key points of the document)

Q: Which do you prioritize: "heat shielding" or "breathable"?
A: The top priority is waterproofing. After ensuring water stoppage with the equivalent of reformed No. 2 or higher, heat insulation and moisture permeation are also considered at an additional point.
Q: What are the tips for DIYing adhesive types?
A: If you observe three points: 1. Base cleaning 2. Genuine primer 3. Air vent roller strong pressure, you can expect to achieve performance comparable to professionals.
Q: Can I first attach the roofing and leave it alone for six months?
A: Modified systems are somewhat resistant to UV rays, but if they thrust in the wind there is a risk of edge breaking. On the safety side, the roofing of the roof will be made within 3 months.

Run checklist to start moving from today

Write down the roof's "area, slope, regional risk, and roofing materials" on paper.
Determine the expected useful life (10-15 years or 30 years grade).
The basic is "Reformed No. 2." If it is slow gradient, strong winds, and many penetrations, we have added "adhesive" and "heat shielding" to prevent heat in the summer.
Calculate the number of rolls and tape amount using the calculation formula and add it to cart.
A moisture content meter, chalk line, air release roller, and full harness were also purchased at the same time.
The installation date is "no rain, low wind, temperature above 5°C."
Non-adhesive use strictly adhere to "100 to the bottom, 100cm wide/200cm long" for adhesive use, and "Primer → Crimping" for adhesive use.
After installation, check the photos, stacked dimensions, and whether or not there are any exposed nails.
The roof is inspected every five years after completion. If you have small holes, first aid can be used with butyl tape.

Summary (reposting key points)

[How much thickness is required?] 】

situation	Approximate thickness required	comment
Vertical thatched roof for general housing (4 cm or more)	1.0mm is OK	Heat shielding Pro class enough cover
Slow slope (less than 3 inches) and snowy and aerial areas	1.2mm or more is safe	Water tends to accumulate, and double-layered and thicker
Large facilities and factory roofs	1.5mm or more is the mainstream	Highly durable products that do not require layering are chosen
Covering method for existing roofs	Adhesive + thick recommended	Because the person you are posting is often not flat

The key points when choosing a roofing are "heat resistance," "durability," and "waterproofness." If you combine it with the roofing material, slope, and regional risks, you won't fail.
Even if you focus on cost performance, if you look at it for a long term, you'll end up with a "reformed No. 2 or higher" value.
The adhesive type is strong, with a focus on slow slopes, strong winds, and rain shutdowns. The key points are base cleaning, primer and crimping.
The key points of the construction are "strictly adhere to stacking dimensions," "doubling valleys and eaves," and "measures against sticking at low temperatures."

"First, get all the tools and draw the reference line with a choke line." Once you've made it this far, all you have to do is stick it according to the steps you follow. Let's put safety first.