Roofing Layers & Why They’re Important?

Any homeowner or child, if asked what is the roof made of (or its roofing layers)? Will answer, it’s the part with the shingles on it, that helps the rain to run down it. They aren’t wrong, but a roof has many roofing layers that together allow it to work properly.

From experience, roofing mission (a.k.a “BulletpRoof”) agrees with homeowners to an extent, except shingles are only a single layer of the entire picture. Let us elaborate further for you.

We’ll be discussing the roof’s layers in this article, from the roof deck up to the shingles. While the anatomy of a roof provides an in-depth look at how the roof forms a system with all of its roof components.

Table of Contents

Purpose of having Roofing Layers

The roof’s layers are meant to help insulate and protect your home; Done by providing proper drainage, ventilation and durability against debris or weather-related damage. By doing so, this helps the water to run-off instead of accumulate and provide enough fresh air to dry areas with moisture quickly. As an added benefit, this cools the home in the summer and keeps the home warm in the winter.

As a homeowner, it’s worth understanding that each roof layer performs one function really well and when it doesn’t there will most likely be a leaky roof in the future.

A Roof’s 12 Layers

A roof is made up of 12 layers from the roof deck up to the roof’s shingles that make up the entire roof’s surface. See them listed from the bottom to the top layer below:

  1. Split-Sheathing; These are equally distanced wood planks that support the roof and provide room for added insulation foam if a roof’s shingles permit it; Specifically cedar shingles don’t allow for insulation foam because they require additional ventilation. The spacing allows it to help ventilate the roof (along with the attic space below it), preventing the growth of mold and rot due to moisture build-up. 
  2. Roof Deck; Plywood base of the roof, that supports the roof covering above it and protects against water passing through to the home below it. Only cedar shingles don’t allow for a roof deck to be installed because they require additional ventilation from the attic to remain viable.   
  3. Battens; Wood planks installed on top of the wood deck to hold concrete, clay or slate tiles stay in place, not used for any other type of shingles. Proper installation allows the tiles to be staggered in a way that allows the water to run from one tile to the next preventing pooling, which requires a skilled roofer to complete. 
  4. Underlayment; A felt paper, tar paper or synthetic material that forms a protective water barrier on top of the roof deck. The material used depends on the location, environment and weather conditions of a region or area where the home is located. An essential waterproofing layer that is both durable to falling debris and assists with insulating the roof. Incorrect installation exposes the roof deck to water, which can result in water-damage, plumbing-damage and/or electrical damage from leaks in the roof deck.  
  5. Ice and Water Shield; An ice-proof and waterproof membrane installed in sensitive roof valleys and around roof penetrations (skylights, air vents, solar panels, etc.). Preventing water from entering these vulnerable joints in the roof’s decking. Incorrect installation exposes the attic space to water, which can result in water-damage, plumbing-damage and/or electrical damage from leaks in the home.
  6. Flashing; Sturdy materials or metal sheets installed on top of the underlayment and under the roof coverings to protect sensitive joints between the roof deck and any roof penetrations (skylights, air vents, solar panels, plumbing, etc.). Incorrect installation exposes the attic space to water, which can result in water-damage, plumbing-damage and/or electrical damage from leaks in the home.
  7. Drip Edge; A metal flashing installed along the roof’s edge, on a roof’s eaves and rakes to form an L-shaped protective cover. Preventing water from reaching the fascia behind the gutters and getting under the roof’s waterproofing to directly damage the interior of a home (severe damage to plumbing, electrical, hvac and the roof are all possible). Required by-law (International Residential Code) and shouldn’t be overlooked due to cost concerns.   
  8. Starter Shingles; A pre-cut row of roofing materials installed at the roof’s edge, on top of the drip edge to add to its existing protection. It has an adhesive seal that helps it to stay in place during high winds and doesn’t allow water to drip anywhere else but the gutters. Incorrect installation allows water to reach the fascia behind the gutters and get under the roof’s waterproofing to directly damage the interior of a home (severe damage to plumbing, electrical, hvac and the roof are all possible).   
  9. Ridge Capping; Pre-bent thicker trim material installed at the roof’s peak where two slopes meet, it easily covers the roof’s ridge. This provides protection at the roof’s peak joints where two sloped roof decks meet. Incorrect installation would mean installing 3-tab shingles in their place because they are not designed to protect that joint and offer many areas for water to leak through into the attic and home.   
  10. Roof Shingles; These are the square and rectangular pieces that cover the middle portion of any roof deck. They are overlapped in such a way to form a tight waterproof membrane that helps water to run-off the roof and into the gutter. While helping to create a sun, water, ice, fire and debris protection that faces the outside elements on your home’s behalf. Its built-in coating on top, is responsible for making it UV-proof and durable against falling debris (making it spring back from impact). Installed incorrectly it allows water to accumulate by blocking it or directing it towards sensitive areas it shouldn’t go.     
  11. Fasteners; These help attach the roof shingles to the underlayment and roof deck that help it to stay tight to the roof deck, preventing water from getting underneath the waterproofing below it. Normally, roofing nails are used for asphalt shingles, and metal fasteners are used for tiles and panels; Other fasteners include bonding, blue tar or adhesive paper. Installed incorrectly, these fasteners can create small holes or gaps in between the shingles, allowing for water to go directly into the attic at times. 
  12. Coatings; A polymer that can be applied on top of the roof shingles and fasteners to restore the UV-protection, water-resistance, fire-resistance and impact-resistance of the roof.

By having all of these roofing layers, it helps to increase the longevity of a roof and by extension the home from getting damaged. For homes in wetter climates, or when it rains there may be noticeable changes with the home that show that these roofing layers are not working as they should.

Commonly, a homeowner will notice these changes in the form of a higher energy bill due to the lack of insulation, dark streaks on ceilings, bulging walls, shingles with moss growing on them, etc. These are signs for a homeowner to keep an eye out for so that they can repair the roof before it takes any major damage in the future.  


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