Roof layers: what's under the shingles (2023)


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Most homeowners never go near the ceiling. When you clean your gutters you probably get a bird's eye view, but little do you realize that your roof is made up of many layers. All you see when you look at the roof is the clapboard, slate or shingles on it.You usually don't care about the layers of mulch that keep your house dry until you have a problem, like attic lights orice damsin the winter.

Roof layers: what's under the shingles (2)

Roofs may seem simple, but they are quite complicated (read:Was the replacement roof done correctly?to show typical problems with roof mounting). There are multiple layers of material, and they need to be installed in the right order...and in the right way to withstand the elements and keep your home dry. For example, an initial course of shingles is installed at the eaves before the shingles are visible.

Roof layers: what's under the shingles (3)

top layer diagram

So we start at the bottom on the deck and work our way up through all the roof layers until we get to the clapboards and sunlight over the roof. This roof ply chart shows the plies that go directly under the shingles plus additional protection for the roof edges.

Roof layers: what's under the shingles (4)
  • Structure– includes the trusses that sit on top of your house and support the weight of all the materials used to construct your roof. Some materials such as ceramic tile and slate are much heavier than asphalt shingles, so the structure must be designed for the materials used.
  • Isolation– In your attic it is used to reduce the loss of warm air from your home. Attic insulation is located in the attic or, when the attic is finished, between the joists above the attic ceiling (read:Isolation doesn't work aloneto find out how it works with the openings in your roof required for ventilation).
  • ventilation– is vital in attics to rid the space of heat and moisture penetrating from the house below. Without proper ventilation, heat and moisture can damage the frame, insulation, and plywood that sits on the joists. You may also encounter mold and mildew problems.
Roof layers: what's under the shingles (5)
  • roof terrace– is the roofing material that sits on top of the roof beams. Most roofing is made of plywood or OSB panels. It is also possible to add a radiation barrier to these 4ft x 8ft tiles as shown above (barrier installed face down).
  • water shield– is the next layer of roof that forms a watertight barrier where ice or water can accumulate near the eaves. It is typically a peel and stick product that sticks directly to the roof deck.
Roof layers: what's under the shingles (6)
  • underbody– usually felt, fiberglass or synthetic rubber (black layer on top) covering the entire roof surface. It's waterproof to let moisture through. This prevents the water from passing through in its liquid form.
  • Tile starter strips- are bought or created by splitting normal tiles in half. They mount to the eaves and face the opposite direction to provide a first line of defense against wind uplift along the edge of the roof.

covering material- this is where most homeowners focus their attention with hundreds of materials, styles and colors to choose from. The five main types of roofing materials are asphalt shingles, cedar shingles, concrete or ceramic shingles, sheet metal and rubber for flat roofs.

Roof layers: what's under the shingles (7)
  • summit openings– are on top of the roof, covered with roofing material but with an opening to allow warm, humid air to escape from the attic.
  • sparkling– is made of sheet metal and is used to prevent water from entering joints where different materials on the roof (and other parts of the outside of your home) meet. Flashing along the eaves is calledDrip edges, and along the chimneys is called staggering. Flasher is also used near skylights, bathroom exits, and other features that protrude from the roof.
Roof layers: what's under the shingles (8)

(Video) Roofing Underlayments EXPLAINED by a roofer: Tar Paper, Synthetic, Ice and Water Shield
Roof layers: what's under the shingles (9)

OneTina Gleisner

Tina helps homeowners create homes they love, homes that support the way we live today. Drawing on her experience of owning 15 homes and running a handyman shop, Tina offers aIntelligent owner report.

reader interactions


  1. Roof layers: what's under the shingles (10)TrophyHouse restoration

    Thank you for letting us know about this! Excellent article!


  2. Roof layers: what's under the shingles (11)Joel Kramer

    Is it "okay" to use OSB to cover a ceiling? I have heard that nails/screws made from this material loosen over time and cause problems with shingles. Thanks very much!

    (Video) How Many Layers of Shingles Can I Have on a Roof? ▬ ROOFING QUICK TIPS


    • Roof layers: what's under the shingles (12)Tina Gleisner

      Joel, OSB is more commonly used than plywood for roof decking because it's just as strong and less expensive. The only area where plywood is better is how it responds to moisture, but there needs to be a water barrier across the roof to avoid this problem. You can learn a lot more about it in this articleOSB vs plywood for roofinggives Atlas Covers.


  3. Roof layers: what's under the shingles (13)hj

    Apparently my ceiling is made out of linear 1×6 pieces of wood. Looks like something got damaged. The company wants me to pay $3,000 to fix it, but they fixed it before they told me. my house is older Was this roof shape more common on older homes? Should the seller have warned me? You were just talking about replacing the plywood panels as you mentioned and that most houses might need 2-3 panels, not $3000 for a 1×6.


    • Roof layers: what's under the shingles (14)Tina Gleisner

      (Video) Roofing How to tell how many layers of roofing you have

      This sounds like a scam, so I'm happy to give you a few ideas. First I must say that I am not a lawyer and you may need to seek legal advice.

      Yes, I've seen boards used for roofs, but only barn boards on homes built in the 1950's or earlier. i found onereporting articlewhich lists various types of canopies including 2×6 boards but are they used when visible inside?

      Even though the old ceiling was 1x6 board, there was absolutely no need to reuse it. All they had to do was remove the 1x6s and install plywood deck panels. If they were as eloquent as the article suggests and claimed they had to remove all the boards to replace just a handful of boards, then they either didn't know what they were doing...or they were creating more work for themselves, which isn't OK . , especially if they were just talking about swapping sheets of plywood.

      I would do this:

      • Have other roofing companies (at least 2) inspect the roof and assess the condition of the roof and shingles and estimate the roof/shingle replacement. Don't be afraid to pay up to $100 for a well-documented report with photos showing what you found.
      • Look at the reports and try to see what work has been done...perhaps too little? What condition is your roof currently or in need of repair? How much should you have charged for the new roof?
      • Decide how much you are willing to pay and offer it to the company along with your receipts.
      • If the company accepts your offer, you pay what you think the job was worth. If they don't take your offer, let them take you to court as it's expensive and there's a 50/50 chance they won't pursue you. The risk here is that they might put a mechanical lien on your property... but not sure if your state requires a signed lease for that.

      I hope I've given you enough ideas to get you up and running and good luck.


  4. Roof layers: what's under the shingles (15)shortcut

    Hey a teammate on my facebook mastermind shared this with everyone
    of us, so I came to see it. I definitely appreciate the information, thanks.


    (Video) What is under the shingles on my roof?
  5. Roof layers: what's under the shingles (16)Gocke-Team

    I have a question about the decking portion of your roof. The plywood must be replaced along with the shingles. I just had my ceiling refinished but there are areas where the ceiling sags like the old plywood wasn't replaced. What is the rule in a roof terrace? We paid $16,000.00 for the roof and assumed the old plywood (roof) would be replaced along with the shingles. That's why we thought we'd pay so much money. Can you help me with my situation what to do.


    • Roof layers: what's under the shingles (17)Tina Gleisner

      Tim, Replacing a roof almost never involves replacing the roofing. You should inspect the plywood for damage and it is very common to replace several full or partial deck sections, but not the entire deck.

      A roofing job usually begins with a sub-floor, a combination ofIce and Water Shieldin the bottom 3 to 6 feet and then a felt-like product over that. The shiny metal around the edges of the roof needs to be replaced, and then your chosen shingles are installed on top of the subfloor... with the bottom layer in a double layer.


      (Video) How to Install Roof Shingles

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What layers go under shingles? ›

What Is Roofing Underlayment? Roofing underlayment is what lies between the shingles and the roof sheathing, or roof deck, which is typically either plywood or OSB. It's installed directly on the roof deck and provides a secondary layer of protection from the elements, including rain, snow, and wind.

What material goes under asphalt shingles? ›

What is roofing felt paper? Sometimes called roofing felt underlayment, roofing tar paper, or roll roofing, this is a layer of protection installed between the roof deck and the roofing shingles.

What is the plastic sheeting under shingles? ›

What Is That Shiny Plastic Film Strip On Shingles? Sealant protection… GAF adds a thin plastic film to keep the sealant from activating while in storage and shipping. This film is protecting the shingles from sealing together while in storage but does not align with the sealant adhesive when the shingles are installed.

What is the layer under the roof called? ›

Underlayment. This felt, or rubberized asphalt sheet, provides an extra layer of protection between your shingles and your roof deck. It helps reduce blow-off by allowing your shingles to lay flatter and more uniformly.

Do you have to put anything under shingles? ›

One question that people often ask is whether or not an underlayment is required beneath asphalt shingles. In general, it's a good idea to use underlayment under any type of roofing, including shingles.

What is plywood under shingles called? ›

Decking. Also known as the wood sheathing, this is the base on which everything else is laid on. It's essentially the foundation of the roof. This is typically made with OSB or oriented strand board or plywood that's attached with nails onto the rafters.

Do I need plywood under shingles? ›

Aside from shingles and underlayment, plywood decking is one of the most important components in your roof. The plywood decking is integral in keeping your home free of unwanted water and mold. If the plywood has gotten wet, it can have a disastrous effect on the rest of your roof, especially the shingles.

What goes down before asphalt? ›

Gravel Layer: Also known as the frost blanket, a mixture of gravel and sand is laid to eliminate the effects of freezing and thawing temperatures. Base Layer: Using bitumen, cement or lime as the predominant binder, a bound base course is laid over the unbound base course.

What are the three types of roofing underlayment? ›

In general, there are three types of roofing underlayment: felt, self-adhered, and synthetic. Each has its own benefits and advantages, and the type you choose generally depends on what your roofing contractor is comfortable with and your local building codes and regulations.

What is the most common underlayment for roofing? ›

One of the most common types of underlayment used in residential, steep-slope applications is black, ashphalt-saturated felt paper. Felt underlayment may be made from either organic or fiberglass substrate, although the organic is much more common. It's called "organic" underlayment because it has a cellulose base.

What is the black stuff under roof shingles? ›

Gloeocapsa magma commonly grows on asphalt shingle roofing because it eats away at the shingles' limestone fillers.

What is the black paper under shingles? ›

Roofing felt or felt paper, also called underlayment or roofing tar paper, goes between the roof deck and the shingles, which adds another layer of protection to your roof. Underlayment has a base made from natural materials like wood cellulose, or synthetics like fiberglass/polyester.

What is the order of roofing materials? ›

We're happy to break the process down for you, step by step.
  • Tear off the old roof. ...
  • Install the drip edge. ...
  • Roll out the underlayment. ...
  • Cover the roof with felt paper. ...
  • Waterproof the valleys. ...
  • Apply starter shingles. ...
  • Install the shingles. ...
  • Install the flashing.

How many layers of roof underlayment do I need? ›

Two layers of underlayment are required for low-slope roofs. The first course is doubled. Above that, 36-inch wide strips are then applied to the roof in a shingle fashion, starting at the lower roof edge, and overlapping subsequent courses a minimum of 19 inches.

Can you put shingles directly on plywood? ›

A: It is never a good idea to install a roof over wet plywood or any type of roof sheathing. Trapped water will boil when the sun heats the roof and the shingles will then have small pits where the steam finally escapes.

What is the waterproof membrane under shingles? ›

The membranes are designed to form a watertight seal around the nail penetrations when shingles are applied. Potentially, covering an entire roof with ice and water protector can prevent leaks even after high wind conditions blow shingles off the roof—preventing further damage and making repair easier.

What should I put down before shingles? ›

Many homeowners don't realize that roofers install a thin layer of felt on the plywood prior to putting down the asphalt riding shingles. This boring layer of black felt, sometimes referred to as tar paper, may not be much to look at but is a crucial step to properly installing a new roof.

Does water get under shingles? ›

That backed-up water can get under the shingles and leak inside. Ice dams can form in as little as 1 or 2 inches of snow. "It's hard to do anything about them after the fact," Crowe says.

Which is better for roof OSB or plywood? ›

Plywood will absorb moisture quicker than OSB, but consequently it will also dry quicker. Both products will swell when wet, but plywood will return to almost its exact shape when it dries. OSB is less forgiving of being left out in the rain and will show more deformities after a wetting and drying cycle.

What is the wood below the roof called? ›

What Is a Soffit? Your roof by necessity, will often times extend over the walls of your home. This overhang can go by a few names, such as the house eaves or the rafters of your roof. The underside of this overhang, when given a finished appearance, is known as the soffit, which means “something fixed underneath”.

Do you need ice and water shield under shingles? ›

Its main purpose is to protect your roof decking if water gets underneath your roofing material (asphalt shingles, metal roof, etc.). It's crucial to have ice and water shield installed on/around certain areas of your roof, like roof valleys, around penetrations, and on roofs that have a 2/12, 3/12, or 4/12 pitch.

What size plywood goes under shingles? ›

Most Common Thickness

The most common rafter spacing is 24 inches, and 5/8-inch plywood is recommended for that. It will support roof loads for most situations and is the standard for most roof applications. Roofs with very heavy loads may require 3/4-inch thickness.

How many bundles of shingles do I need to cover a sheet of plywood? ›

Each plywood sheet is 4 x 8 feet or 32 square feet, which coincidentally is almost exactly equivalent to the coverage of one bundle of traditional three-tab shingles.

What is the best sub base for asphalt? ›

The secret to having the best asphalt driveway is by having a solid base. Using quality crushed gravel as a base to your blacktop will surely give you the perfect driveway quality that will last for a very long time.

What is the first layer of asphalt called? ›

Subgrade. Once the dirt is prepared, contractors lay down the subgrade. The subgrade is the most important part of the entire design, setting down the very foundation of the pavement.

How much gravel do you need under asphalt? ›

Keep in mind that the gravel base under the blacktop is where the driveway gets almost all its strength. You want at least 8 inches of crushed compacted gravel under the blacktop.

What do roofers use now instead of tar paper? ›

For roofers, Synthetic Roofing felt is much safer during installation because there is a gripping surface that prevents slipping or falling. Tar paper and roofing felt are somewhat similar in that they both shed water.

What is the easiest roofing material to install? ›

Asphalt shingles are popular because they blend looks, longevity, and a reasonable price, and they're typically the easiest to install, saving you money on labor costs as well. Specialty roofing materials like slate, tile, and metal tend to cost much more, but they can also last much longer—and they look nicer.

Is 30 lb felt better than synthetic underlayment? ›

With that in mind, synthetic underlayment is more durable than felt underlayment. Felt underlayment is much more prone to rip from high winds and during the installation process. Synthetic underlayment also holds nails better and repels water instead of absorbing it.

What roofing underlayment is waterproof? ›

Non-bitumen synthetic roofing underlayment is known for being highly flexible, waterproof, durable, and mold-resistant. Compared to rubberized asphalt, synthetic underlayment is exceptionally lightweight.

What is a good thickness for underlayment? ›

It comprises padding materials and is typically about 1/4 to 1/2 inch in thickness. The purpose of the underlayment is to provide a sturdy yet comfortable layer for your outer flooring to sit on. Underlayment can be made of wood or even cement, but most often is some type of foam padding.

Should I use nails or screws for underlayment? ›

Screws are preferred over nails for subfloor and underlayment installations as they provide strong and tight connections that help prevent the floor from squeaking. Before starting your next subfloor or underlayment installation, make sure you have the right subfloor screw gun for the job.

Do you need black paper under shingles? ›

Answer: Roofing felt is a layer of tar paper installed beneath the shingles to provide a backup waterproof membrane in case of leakage. Felt, otherwise known as underpayment, is required when asphalt shingles are installed as a first layer of roofing or when they are applied over wood shingles or a built-up roof.

Is shingle debris toxic? ›

Are Roof Shingles Toxic? Modern shingles can be toxic during installation, but they will usually not be harmful unless you're trying to collect potable rainwater from the roof; chemical constituents in the shingles can find their way into the run-off water.

What is the roof moss killer? ›

Roof Moss Killer is used to effectively remove moss and kill growth spores quickly. It is the preferred product used by commercial roof cleaning companies throughout the UK.

How many layers of underlayment do I need for a 2 12 roof? ›

For roofs with slopes of 4:12 or greater, one layer of underlayment is required. For roofs with slopes between 2:12 and 4:12, 19” laps of underlayment is required, starting with a 19" strip, then full sheets.

How long does roof underlay last? ›

Asphalt felt, the most common type of underlayment has a lifespan of between 20 to 30 years. However, in extreme extended conditions, its lifespan can be cut by half. Fortunately, new rubberised or synthetic asphalt underlayment has a longer lifespan of between 25 and 35 years.

Does underlayment go over the ridge? ›

For ridges, the underlayment should … be lapped over the ridge at least 4” (102 mm) to 6” (152 mm) as would be done on a new or complete tear-off installation.

Do you put plywood under shingles? ›

Underneath all the shingles and underlayment has a layer of plywood decking. That layer is the last line of defense between the inside of your home and the outside world. Eventually, the underlying plywood decking may need to be replaced, here's what you should know about it.

What type of underlay should be used beneath wood shingles? ›

Felt underlayments are usually made from synthetics such as fiberglass or natural materials like wood cellulose. They're then layered with a protective asphalt coating to defend against debris and moisture. This is a traditional underlayment option for cedar shingles.

What are the three layers on a roof? ›

And when you do replace your roofing, there are three main layers that have to be addressed: the roof deck, underlayment, and the shingles themselves.

How many layers go on a roof? ›

In most states, you're only allowed to have 2 layers of shingles on a roof for fire safety reasons. However, you'll still see roofs that have 3 or 4 layers today. If you already have 2 or more layers, a contractor will recommend a full replacement.

What should I use for roof underlayment? ›

Synthetic Underlayment

This is currently the most popular choice for roof underlayment, and with good reason. Made with an asphalt-saturated basemat and fortified with a mix of fiberglass, this product is not only extremely water-resistant, much stronger and more resistant to tears than other types of underlayment.

What paper goes under roof shingles? ›

Roofing felt or felt paper, also called underlayment or roofing tar paper, goes between the roof deck and the shingles, which adds another layer of protection to your roof. Underlayment has a base made from natural materials like wood cellulose, or synthetics like fiberglass/polyester.

What needs to be attached to the sheathing before the shingles can be placed? ›

Underlayment— This is the first layer of waterproofing that goes down in between sheathing and shingles. Underlayment seals the roof from damaging elements like snow, ice and rain. Also referred to as a membrane, underlayment is mandatory for providing the roof with a waterproof barrier.

What can you seal under roof shingles for water leaking? ›

The Silicone Roof Sealant

Silicone roof sealant is also a great option to fill in shingle cracks and leaky nail holes and is also used to repair folded or slightly lifted shingles. A small, droplet-like amount of silicone will have to be placed with a caulk gun under the bent part of the shingle.

Do you need a drip edge with shingles? ›

Without a drip edge, water may end up beneath the shingles and may cause damage to various parts of the home. Though your home may not have originally had a drip edge installed, drip edges are now required by most building codes across North America to protect homes from damage.

Do shingles need to hang over drip edge? ›

Shingles should be installed over the drip edge a minimum of 3/8” (9 mm) at both the eave edge and the rake edge. If the drip edge extends… out from the rakes and eaves (typically called DL Style or D Type), the shingles may be installed flush with the drip edge.


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2. What Homeowners Should Know About Roofing Underlayment
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3. Multiple Layers of Asphalt Shingles
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4. Roofing Video - Asphalt shingles : Laying a second layer over existing shingles roof.
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5. Pros and Cons of Roof Overlay
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6. Two Layers of Shingles? Bad Idea!!
(Stones River Roofing)
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