Did you know that a new roof can raise the resale value of a home by approximately $12000? Well, a roof is more than shingles that are visible from outside.

It just the most visible part and an important feature that gives the home some edge as well as keeping the dweller safe.
A roof comprises three main components; the deck, the underlayment, and the shingles.

Underlayment also protects your home from damage caused by rough weather conditions like heavy rains, ice, or snow. Less known or talked about is the roof underlayment types that lies beneath it and the second in the line of defense in the protection of the building. It plays a role in preventing damages and leakages in a building. It also protects the deck from deterioration by chemicals from the shingles.

Underlayment is a layer of material used as a barrier to keep water from penetrating through incase the outer roof (shingles) is damaged. The underlayment is placed between the roof deck and the visible outer roofing material.

When water gets trapped under the shingles, it can leak through the deck. This not only caused damage to the deck but to the ceiling as well. The purpose of underlayment is to ensure that that water does not pass through to the deck.

It protects the deck from water damage before the shingles are installed. Its use is believed to have originated from the use of tar paper. This material was used by miners during the California gold-rush in the early 1800s to roof their temporary structures. The use of tar paper as an underlayment was then born. It has since evolved and advanced to three main types currently, as discussed in this post.

When installing shingles, one cannot fix directly onto the roof deck. If this were to be done, any damage to the shingles would cause water to sip right onto the deck, destroying the building. This kind of damage is not only a health hazard but also devalues a building. A good underlayment should give a home a healthy lifespan and minimize the cost of repairs.

Let’s have a deeper look into roof underlayment now.

The main types of underlayment are as below:

  • Asphalt-Saturated Felt Underlayment
  • Non-Bitumen Synthetic Underlayment
  • Rubberized Asphalt Underlayment
asphalt-saturated felt roof underlayment

Asphalt-Saturated Felt Underlayment

Commonly referred to as “Felt paper,” is the oldest type of underlayment and has been the most popular choice for most builders. That is before the synthetic underlayment came to be.

It has been in use for about 100 years and continues to be used today. It is made from a mixture of beaten/pulped paper and fabric soaked in asphalt .

It is made to repel water and is relatively cheap due to its manufacturing process and the availability of materials used.

The cost of roofing felt per square for ranges between $0.39 and $0.58. Installation averages at $ 55.20 per hour.

Pros of Asphalt-Saturated Felt Underlayment

  • It is relatively cheaper
  • Good for hot and dry weathered states like Arizona
  • Readily available
  • Has been tried and tested by time
  • Slope limitation requirements that allow overlap giving a double layer for enhanced protection.
  • Familiarity

Cons of Asphalt-Saturated Felt Underlayment

  • Has a shorter life span of around 15-20 years
  • Hard to install due to its lack of elasticity
  • It is not waterproof
  • Gets easily destroyed by heat from roofing material and severe sunlight
  • It is heavy and comes in two varieties, 15 pounds and 30 pounds.
non-bitumen synthetic roof underlayment

Non-Bitumen Synthetic Underlayment

Synthetic Underlayment is the most modern the most commonly used method today. It has been in use since the early 2000s.

Synthetic Underlayment is made from hard-wearing plastics by soaking base mat mixed with a mixture of fiberglass/polyester. This makes it water-resistant, stronger, and more durable. It does not absorb moisture hence prohibits the growth of mildew on the deck.

It does not get destroyed by its exposure to UV rays. It is also way lighter than felt. It also has anti-skid properties that make the installation process easier. It has gained a huge following after hurricane Katrina in New Orleans.

After the hurricane, contractors used synthetic underlayment temporarily as the buildings were being repaired. It was found to withstand the elements as long as six months.

This underlayment’s approximate cost is $59.97 for 10 square foot while the average cost of installing it is per square foot $4.00- $5.55. This may vary from contractor to contractor; get a few estimates before settling on one.

Pros of Non-Bitumen Synthetic Underlayment

  • Easy to install and has an anti-slip surface
  • More durable and can last up to 12 times the lifespan of asphalt
  • It does not absorb moisture, therefore, prohibits the growth of fungi and mold
  • It is light in weight
  • It has a longer lifespan of 25-30 plus years
  • It is made of polypropylene and polyethylene, materials that can be recycled.

Cons of Non-Bitumen Synthetic Underlayment

  • It is quite pricey and can cost five times more than asphalt, making it least ideal for low budget builders.
rubberized asphalt roof underlayment

Rubberized Asphalt Underlayment

As the name suggests, it contains rubberized bitumen in but in small quantities and made into sheets. It has a higher amount of asphalt and rubber polymers. It is highly elastic, making it a perfect choice for areas that experience extremes in hot or cold weather conditions.

High concentration of rubber and asphalt polymers makes it completely waterproof. This quality is causing it to be seen as the premier underlayment and most expensive among the rest.

It is the advised option for the very wet, cold, and snowy areas. It works well on any roof due to its flexibility. It has been in use around the same time as the non-bitumen synthetic underlayment.

There are many varieties, some more costly than others with cost averaging at $130 per 10 square foot roll. One can get actual prices by getting quotations from a local roofing expert.

Pros of Rubberized Asphalt Underlayment

  • The only underlayment that is waterproof
  • It is easy to install because it is self-adhering
  • They have a long lifespan
  • It is highly resistant to the sun’s ultraviolet rays.
  • Durable.
  • Easy to repair.

Cons of Rubberized Asphalt Underlayment

  • It is expensive
  • Heavy and thus labor extensive

When it comes to choosing underlayment, a lot of factors have to be considered. The lifespan of an underlayment is an important factor to consider. If there are plans to change the entire roof soon, one that is cheaper and with a shorter lifespan would be a better choice.

I found synthetic roof underlayment is best among all. It’s lighter than the rest. It is also more tear-resistant when being installed compared to asphalt felt underlayment.

However, the synthetic roof underlayment is quite expensive. If the budget does not allow, go for what is suitable for you by looking at these other factors.

Area Climate

The local climate should be a major factor when considering the type of underlayment needed. Different materials react in different ways when exposed to too much heat or water. In New York, for example, the weather ranges from cold and windy to warm and humid. This means that the underlayment gets exposed to more moisture, which will eventually affect it. You cannot use the same underlayment material in areas with severe rainstorms, snow, and ice as those that are relatively dry. Florida and Texas are not just same.

Roof Design

The roof design can affect the performance of an underlayment. The roof’s ability to remove water or moisture. Some prevent water and moisture from getting trapped. In contrast, others trap it, exposing the underlayment to too much wetness, leading to a significantly shorter lifespan. Low sloped roofs should need a more water-resistant underlayment because of their inability to drain water properly.

Roofing Type

Choose an underlayment that goes with the roofing material. Incompatibility can cause damages to the underlayment. Having a poor rooftop can weaken the functional capability of the underlayment and efficiency. The roofing material should complement the underlayment.

Local Laws

In Florida, the building Code forbids the usage of No. 15 felt asphalt. However, it allows the use of the heavier No. 30 felt asphalt, but that can only be used if applied in two layers. This code has pushed many homeowners and developers to seek alternative underlayment types. So, complying with local laws is important.

The Contractor

The contractor hired to install the underlayment can make or ruin your roof. Suppose the installation of the underlayment is poorly done. You will undergo damage to the deck, and so the entire building. Bad installation methods can damage the material as well as premature failure.

The use of plastic caps and roofing nails are recommended. Staples often leave room for water to penetrate the deck.

The underlayment should wrap around the edges to avoid water penetration and moisture, causing damage to the structure. Remember, synthetic underlayment is not self-sealing and so the need to wrap around the edges. A good contractor will ensure the installation is done right.

The Budget

The underlayment may be a good choice in all other aspects but maybe beyond one’s budget. The funds available by default will influence the choice.

An underlayment inspection is done to determine the underlayment’s integrity and how long it will last. The inspector is likely to check the ceiling and the attic to determine the underlayment’s general condition. If there is an indication that it is damaged, a detailed inspection can be carried out.

Roof repairs can be costly but what will cost more is to replace it entirely. It is advised to do a regular inspection and ensure the roof’s right condition at all times. This keeps one conscious of the status of the underlayment. It is practically impossible to inspect an underlayment only without touching the roof’s other components.

Underlayment inspection and general roof inspection should be carried out at least twice a year and after an extreme weather season or storm. The owner can do a primary assessment. However, a professional roofer is required when the underlayment inspection is for insurance or sale reasons.

Aa a homeowner you should:

  • Look out for visibly damaged outer roof
  • Clean the gutters regularly
  • Inspect the attic for signs of water seepage
  • Look out for areas with potential water damage

Perform a roof underlayment inspection when you notice:

Water Stains on the Ceiling

Water stains on the ceiling are a telltale sign that the underlayment is damaged and water is leaking. It can signify the weakening of the underlayment due to age and other factors.

Missing or Curled Shingles

If some shingles are missing, it is good to check the underlayment to ascertain if there has been any damage. Missing or worn out shingles mean that the underlayment is contacting more water than is desired.

If you are buying or selling a home, an underlayment inspection is important for insurance and valuation purposes. This is to determine its condition because a roof carries a lot of value. It helps to know the amount of work that the underlayment may need. Also, after every season or when you sense the need to inspect.

roof underlayment types

According to homeadvisor.com, a primary roof inspection ranges between $119 and $303. The costs may vary depending on; climate, the size of the home, the reason, and the amount of expertise required. 

An underlayment inspection can be used to determine the followings:

  • Whether an underlayment is installed according to the right specifications. The overlapping may have been incorrectly done or the sealing around chimneys and the roof edges.
  • Whether there is any damage to the underlayment. It can be caused by tears while installing and holes caused by fasteners.
  • Whether the underlayment is compatible with the roofing material.
  • Whether the underlayment needs to be repaired or replaced.
  • The age of the underlayment and estimated lifespan
  • If the underlayment is a hazard in any way
  • The value of insurance policy
  • A portion of the value of a home
Last Words

If a roof is not functioning as it should, the whole building is affected. A good ceiling is essential to any building. When selecting a roof underlayment types, there are many factors to consider. The underlayment of choice should be a balance between all these factors.

Without proper roofing, even a good home can get ruined, and its quality brought down. It can also put a household at risk of dangers brought by extreme weather fluctuations and other exterior factors. The underlayment, though not visible, is vital to any roofing system.


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