What is Ridge Cap (Mune Bankin)? What Issues Arise from Deterioration!? We Will Also Introduce Some Installation Examples!

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

Here, we will introduce “What is a ridge cap?” and also present construction examples!

What is a ridge cap?

First of all, the “ridge” in ridge cap refers to the roofing material installed at the highest point of a detached house. It consists of a base material called “nukiita” placed over the joints of the roof, with a metal sheet covering it.

Since the top of the roof is not covered by roofing material, it is protected by the ridge cap, which acts as a cover to safeguard the critical area of the roof!

The ridge cap applied to the ridge is fixed with nails or screws from the side, and often, the deterioration symptoms are caused by these becoming loose.

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Beware of unscrupulous contractors!

The ridge cap is often pointed out by door-to-door salespeople and cold callers.

“The ridge cap is peeling off”
“The ridge cap is lifting”
“I saw it peeling off while working nearby”

They may ring the doorbell pretending to be craftsmen and approach you.

There are cases where they genuinely inform you of a peeling issue, but
even when there are no actual problems, they may still point it out, and if you let them onto the roof, there is a risk of them damaging other areas.

If approached as mentioned above, it might be a good idea to take their business card and research online before requesting any work or inspection later.

In the case of malicious contractors, there is a high possibility that they do not have a website or have a bad reputation!

Base for Ridge Cap

There are different types of batten used under the ridge cap.

Originally, wooden boards were used, but recently, resin-based battens have become more common.

Despite the differences in type, they are all uniformly referred to as battens.

Here, we will explain the types of battens.

Wooden Board

Wooden boards have been widely used as the base for ridge caps. In Japan, cedar is commonly used due to its lightweight and ease of processing.

However, wooden boards are weak against moisture and can quickly rot if there are gaps.

If the base of the ridge cap deteriorates, it can affect the entire roof, so their use has decreased recently, but cedar battens still seem to be the mainstream choice.

The lifespan of cedar battens is approximately 10 to 15 years.

The method of fixing the ridge cap is only with nails, as using screws can cause the wooden batten to split.

Resin-Based

This is a resin-based batten that we have been using frequently recently.

Since it is made of resin, it does not corrode like wooden boards. It is also less likely to absorb moisture, resulting in a longer lifespan and fewer issues compared to wooden boards.

The durability is said to be about three times that of wooden boards!

However, it is not all good, as resin-based battens can crack. If the position of the nails or screws used for fastening is incorrect, it may not secure properly and could crack.

It is essential to carefully choose the contractor, as a poor choice can significantly reduce the lifespan of the roof that should last longer!

Deterioration of Ridge Cap

~Why do nails start to lift?~

① Due to Strong Winds

The ridge cap is located at the highest point of the roof, making it susceptible to wind effects, and it withstands the wind pressure from gusts, strong winds, or typhoons solely with nails.

If the wind continues to blow or blows incessantly, it resembles a state where nails are being pulled out while shaking, causing the nails to gradually loosen.

② Caused by thermal expansion

“Thermal expansion” is the phenomenon that occurs when metals expand when heated.

Since the ridge cap is made of metal, it expands due to the sun’s heat during the day and contracts when the temperature drops at night. When expanding, only the metal sheet contracts, and by repeatedly expanding and contracting over a long period, the nails gradually become loose.

In houses with good sunlight, the speed at which nails loosen also increases, so after 7 years of construction, it becomes necessary to check the nails.

~ Symptoms of deterioration caused by loose nails ~

① Corrosion of the purlin

The purlin is covered by the ridge cap, but rainwater gradually seeps in through small gaps such as the joints of the ridge cap, nail holes, and the lifting of the metal sheet.

Especially since the purlin is made of wood, it is weak to moisture, and the rainwater that intrudes accelerates the deterioration of the purlin.

② Occurrence of unusual noises

When nails are lifted or come off, the ridge cap may lift and be blown by strong winds, causing unusual noises.

Corrosion of the purlin can also prevent the ridge cap from being securely fixed, which can also be a cause of unusual noises.

③ Displacement of the ridge cap

Exposed to rainwater, the ridge cap may lift or become displaced. If the ridge cap is displaced and falls, it poses a risk of accidents by hitting people or buildings, so caution is necessary.

If you notice that the ridge cap is lifting, we recommend early maintenance.

Ridge Cap Metal Repair Method

The repair method for ridge cap metal generally follows the steps below.

Removal

Remove the existing ridge cap metal. This is a dangerous task at heights, so we will proceed with caution.

Installation of Underlayment (Nailing Board)

If the underlayment is also damaged, it needs to be newly installed. (Nailing Board Replacement)

Especially if the nails of the ridge cap metal are coming loose, there is a high possibility that the underlayment has rotted due to rain leaks or deterioration.

If the underlayment remains in a deteriorated state, there is a risk that the new ridge cap metal will have nails coming loose or cause rain leaks shortly after installation. Therefore, regular maintenance of the underlayment is necessary.

Replacement

Once the underlayment is prepared, install the new ridge cap metal. Secure the ridge cap metal with nails to the nailing board, and fill the joints with sealing material. The sealing material is applied to the inside of the joints, so it is not visible from the outside!

The sealing material is a flexible paste-like substance. Most often, a modified silicone material is used!

It has waterproof and airtight properties, joining the seams of building materials like ridge cap metal, enhancing waterproof functionality and preventing scattering due to strong winds.

Examples of Ridge Cap Metal Replacement Work by Kakeru Koumuten Co., Ltd.

The ridge metal used in the photos is made of Galvalume steel from Toko!

The damage caused by ridge metal peeling increases dramatically during typhoon season.

To prevent this, we recommend regular maintenance!

Watch our video about ridge metal replacement at Kakeru Koumuten

Conclusion

How was that? If you’re thinking about checking your roof for an overlay or ridge metal inspection, please contact Kakeru Koumuten! Estimates and inspections are, of course, free!

We prioritize our customers and are confident in our work!

No matter how small the job, we are happy to assist you!

Kakeru Koumuten does not charge until you are satisfied after the work is completed!

If you have any concerns after the work, or if you’re not completely satisfied, please feel free to consult us, and we will respond promptly!

 

We welcome consultations via LINE◎

 

 

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!