The Layers of Your Roof: What’s Beneath the Shingles?

Take a moment; stare out the window, at the sea of roofs beyond. What do you see? Tiles, shingles, asphalt or perhaps concrete. But below the hard shell, is a complex series of layers serving vital functions for your home. As with all things in life, you don’t even know they’re there until something goes wrong. But since these layers keep out the elements all year round, it can be useful to understand their purpose. That way, when something does go wrong, or you need to get roof repairs in Cambridge, you know how each layer interconnects and functions. 

If you don’t know what you’re doing with your roof – that’s no problem! We will happily help you with any problems you face.

Just get in contact with us and we will visit you, wherever you are, and give your roof an inspection!


The framing refers to the roof trusses, which will support the weight of the roof, transferring it into the structure of the house. A sturdy frame is crucial for heavy roofs made of ceramic tile or slate.  Beams of timber or metal are standard in the US, whereas bamboo is the material of choice in Eastern Asia.


Insulation reduces heat or air loss rising from the attic, out of the house. Without proper insulation, homes are inefficient, losing heat readily. Insulation is typically added between the rafters. Interestingly, insulation also slows the transfer of heat from outside to the inside in summer, keeping the home cool.


The attic isn’t just a space for storing junk: it’s part of the roof itself. Keeping the attic ventilated is essential for the longevity of the roof. Therefore, ventilation systems, e.g. ridge vents or gable vents, are used to decrease the chance of ice dams and prolong the lifespan of the roof. By reducing the moisture which gathers, the ventilation system prevents the formation of mould and mildew.

Roof Deck

Resting on the trusses, the roof deck is the layer upon which the shingles are attached. Roof decks are customarily composed of plywood sheets.

Starter Shingles

A starter strip of special shingles can be used to line the edges of the roof. They seal the edge; thereby, increasing the punishment the roof can withstand from the wind and rain.

Water Shield

A waterproof membrane with a polymer-modified bitumen adhesive back is added over the deck – to ensure water or ice doesn’t penetrate the attic – forming a watertight seal. Even a nail going through won’t affect its functioning.


A protective layer is applied to reduce blow-off from shingles by helping them to lay flatter and more uniformly. For different roofing materials, a different underlayment will be used.  


Finally, the layer everyone knows can be applied. Shingle or shake, tile, metal and wood – or for the classic look, slate can be used. The shingle or outer layer serves an essential purpose, as well as forming the aesthetic and architectural casing of the house. Without it, a home would be like a tortoise without a shell: naked.

Ridge Vents

Lastly, flashing or ridge caps are used to seal the seams – usually made of metal, e.g. zinc. They ensure water cannot get between the edges of the roof.


More than shingles: the layers of roofs

What’s underneath your shingles