Planning on replacing your roof? Ever wondered what type of roof underlayment you should use? This is not an uncommon question for Central Florida homeowners to ask. And as simple as the answer may seem, if you are planning to have a new roof installed the typical response you will often get from a professional roofing contractor is…”We use product xyz for all our reroofs. It’s the best!” or “It depends“. While many owners may be perfectly satisfied with the first answer, it’s really the second you should be asking for more details about! Depends on what? Well, here are a few things to consider and will help guide you in choosing the best roofing underlayment for your house:
- Slope of The Roof – The slope or pitch of your roof can determine what kind of underlayment should be used. In Florida, building codes will dictate the minimum requirements for both the types of acceptable materials that can be used and the installation specifications. If you are working with a licensed and insured roofer they will be able to advise you on what is an acceptable underlayment for your roof and what is not. It is important to understand this because depending on the slope of your roof, your options may be very limited and will inevitably affect the total price of the job.
- Type of Roof To Be Installed – For decades, 15lb or 30lb roof felt has traditionally been used as an underlayment prior to the installation of asphalt shingles in order to “dry-in” the roof. However, for a tile roof, most Florida roofers will install some kind of rubberized roofing underlayment due to the low roof pitch of tiled roofs. This can include modified bitumen rolled roofing that is torch applied, or a peel-and-stick synthetic underlayment (see below). These superior underlayments provide the additional protection the home needs for that specific type of roof.
- Cost – Your local roofer may offer an “upgraded” roofing felt for your project that will add cost to the total price of the roofing job. If you are tight on budget, then you may want to stick with the standard option. Also, when requesting estimates from multiple roofing contractors, you should make sure that you are comparing prices with the same materials to be used. Otherwise it may be difficult to understand the reason for the price difference from one bid to another, not to mention potentially miss out on a good deal. Always compare apples-to-apples in order to get the most competive pricing!
3 Most Common Types of Roofing Underlayments
There are a vast array of roofing underlayments available to select from if you are shopping by brand. However, it really just boils down to just 3 main categories. Here is a list of the 3 most common categories of underlayments:
- Asphalt Saturated (Felt Paper)
- Synthetic Underlayments
- Modified Bitumen or Peel-and-Stick Underlayments
Asphalt Felt Paper Underlayments
As mentioned above, felt underlayments have been used for many years on residential roofs. There are typically made up of a fiberglass mesh material that is impregnated with asphalt. The asphalt makes felt water resistant, but hardly water-proof. It can only be exposed to the weather for a short period of time before it fails. Asphalt felt comes in 2 different thicknesses. 15lb felt is the thinnest and because of that, it is prone to tearing easily. 30lb felt is noticably thicker, less flexible and slightly more resistant to tearing.
Pros & Cons of Synthetic Underlayments
Synthetic underlayments are typically made of polyethylene or polypropylene and in some cases recycled materials.
Some of the advantages of synthetic underlayments include its high strength and tear resistance, water repellent properties as well as safety features, such as a non-splip surface. In addition, they have UV resistant properties that allow for a longer exposure period. They are also considered a sustainable product due to the fact they can be recycled and reused.
There has been somewhat of a debate over synthetics and their permeability properties (allowing water vapor or moisture to pass in one direction or the other) which allows for the roofing materials to dry properly. High permeability means more moisture will pass and low permeability means less moisture will pass. Owens Corning did a test on this that you can read here and will explain it better. The bottom line is, if your attic is well ventilated and you use a synthetic underlayment with shingles, you should have no issues with moisture as mentioned in the study.
In recent years, synthetic polymer underlayments have risen in popularity and there are several reasons for this. For the roof replacement specialist, changes in the code requirements and the fact that synthetics are easier to work with and generally safer and faster to install. This is due to their lighter weight and ease of handling and non-skid features. For the homeowner, synthetic roof underlayments offer better protection, resistance to tears and a longer warranty period.
Rubberized Roofing Underlayments
Modified Bitumen Membranes – These are roofing materials that come in a roll and are typically coated with the same granuals you would see on shingles. The difference between an actual shingle and rolled roofing is instead of the base layer being a fiberglass material, modified rolls are made of a rubberized bitumen material that is applied by rolling out sections and using a torch to heat the material so it sticks to the roof deck. They are often seen on flat roofs or low-pitched roofs and when installed properly are essentially a complete roofing system. As mentioned above, they are commonly used as the underlayment on tile roofing systems.
Synthetic Peel-And-Stick Membranes
These are made up of a combination of a synthetic polymer layer on top of a self-adhering rubberized bitumen material that is similar to the rolled roofing, but does not require heating in order to be applied to the roof deck. The most common use for this material originally was for colder climates under the name of Ice and Water Shield and is applied around the eaves and valleys where snow tends to accumulate. However, in recent years, roofing professionals in Florida have been using it on the roof valleys and around chimneys due to it’s excellent water proofing properties. The reasons for this are because when the shingles are installed over this material, the nail holes are sealed by the membrane below. Traditionally, metal valley flashing has been installed with nails and had a tendancy to leak over time. It is not uncommon to see it being used on tile and metal roofs as well.
So Exactly Which Roof Underlayment Should You Choose?
As you can see, there are several things to consider in order to answer that question accurately. Luckily, most experienced roofing companies will have a preference on which underlayment they choose to replace your roof with based on the climate and overall performance of the product. If you want peace of mind and have the budget, go with a synthetic peel-and-stick membrane. Why? Because almost all other underlayments are inferior due to the simple fact that once you start nailing the shingles on, there is the potential to leak where the nails penetrate the underlayment. As mentioned above, with a quality peel-and-stick product, nail holes are sealed.
Of course, If you are still unsure of what underlayment you should select to reroof your home, contact Doug Oliver Development and make an appointment to speak to a licensed roofing contractor that can help answer any questions or concerns!