Back in the day, roofers would commonly use an asphaltic felt paper underlayment. While traditional roofing would use felt as an underlayment, a growing market demands more alternatives like synthetic underlayment. Most people think of roofs only think of the shingles on top of it, but they often put a layer of protection underneath the roof.
What is a Synthetic Underlayment?
Felt was traditionally a thin water-shedding barrier to keep the water out of your roof, which could be disastrous if it got in. The shingles will stop much of the water, but without the underlayment, the water would still penetrate the roof.
When we talk about synthetic underlayment, we mean that you have a layer of laminated polyethylene plastic material or laminated polypropylene. It goes over the deck of the roof as an extra layer of protection for the roof. You can buy synthetic underlayment in a broad selection of thicknesses. Synthetic underlayment has existed in the market for over 20 years.
Synthetic underlayment often weighs less than traditional felt for the roof, and some of the products will have a layered design. The extra weight from traditional felt can make it harder to roof with, which explains why some roofers prefer synthetic underlayment.
Advantages of Synthetic Underlayment
Synthetic underlayment offers even better water protection than traditional felt. We cannot say that it’s waterproof because while it can shed water, some water can still enter, especially around the fasteners. You can buy synthetic underlayment either as waterproof or water resistant. Waterproofing will cost more, but it should give you total protection no matter how the roofer installs it.
Water-resistant underlayment leaks where the underlayment gets punctured with fasteners. Synthetic underlayment often consists of long-lasting polymers that add to the strength and longevity of your roof.
When you hire a roofer who understands how to install synthetic underlayment, it will give you much better protection than traditional felt. Synthetic roof underlayment is also incredibly durable, and it can handle extended UV and moisture exposure. As we said before, synthetic underlayment also tends to be lighter than traditional felt. In many cases, it will be up to four times lighter, which makes it much easier to install.
You can install synthetic underlayment much faster than you could traditional felt. Synthetic underlayment comes in wider and longer rolls than traditional felt. That means making fewer trips up the ladder, which is one of the bigger risks of roofing. To give you an idea of how much more efficient this is, a 2700-square-foot home might use three rolls of synthetic underlayment. Contrasted with traditional felt, you will use about 14 rolls to cover the same area.
Synthetic underlayment is less slippery than traditional felt making it safer for roofers. Even experts in roofing face a real danger in this line of work. Also, because this synthetic underlayment consists of plastic, it will typically resist mold growth. Mold growth is one of the most costly problems that a homeowner can face when they don’t act fast enough. Roof algae and mold are the biggest dangers that you can face.
To sum up the advantages:
- Less slippery and safer
- Weighs less making it easier to roof with
- Less prone to roof mold
- More durable than traditional felt
- Make fewer trips up the roof
Disadvantages of Synthetic Underlayment
Now, you do have things with a synthetic underlayment that take away from its strengths. For example, the biggest drawback to synthetic underlayment would be if you looked at the costs associated with it. You will pay far more for the investment of a synthetic underlayment than with traditional felt. The cost of synthetic underlayment decreases with the more you buy. In general, you can expect it to cost $0.15 to $0.65 per square foot. In general, the more you pay, the better quality of the materials.
Now, let’s highlight another distinct disadvantage of going with synthetic underlayment. That disadvantage is that you don’t have a standardized system with synthetic underlayment. Before you buy synthetic underlayment, you need to do heavy research because not all companies will offer the same quality. In some cases, you could pay more thinking you will get a better deal when it just won’t be the case.
Some companies will offer a far inferior product, and in some cases, it can even be worse than traditional felt. Manufacturers in this field may make their synthetic underlayment differently, which can be a disadvantage if you don’t know what to look for. Performance can live or die based on the company that you choose.
You want to speak with a trusted contractor on this topic who will help you to select the right roofing materials. You don’t want to hire someone who will cut corners when it comes to your roof because it will lead to inferior results. RGB Construction offers residential roofing services that you can trust, and they’re a veteran-owned business.
To sum up the disadvantages of a synthetic underlayment, they include:
- No standardized system for quality
- More costly than traditional felt
Traditional Felt Underlayment: What to Know
Roofing felt has another commonly known name that you probably heard before called tar paper. Traditional felt underlayment is still the most commonly used underlayment for roofing due to price barriers. It’s also one of the oldest choices. Manufacturers saturate paper or fiberglass mats with asphalt. You can buy felt in two types: No. 15 or No. 30 felt. Generally speaking, you want to choose No. 30 over No. 15 because of its greater thickness and strength. No. 30 won’t tear or rip as easily as No. 15.
Advantages of Traditional Felt
The biggest reason that people buy felt is because of the more affordable cost. You can pay as little as $0.05 per square foot. For the more expensive ones, they can cost up to $0.90. Typically, you will buy it in square-foot rolls of 100, 200, 500, or 1,000-square-foot rolls.
Wool felt also tends to be exceptionally flame retardant, and while it won’t stop a fire from burning down the home, it can extinguish a flame if it starts on the roof. This textile also has sound-dampening properties, which will keep external noise pollution from entering the home.
Another advantage is that felt roofs lend themselves well to flexibility, and you can install them on just about any roof regardless of the size or structure. You can also buy them in various colors that will match your environment.
Also, traditional felt repairs quite easily in the event that it suffered damage. We should say that in terms of short-term repairs, they will be quick and painless. You could even repair the felt yourself if you have a split in the felt, but the dangers of going up on the roof make it so that many prefer to hire a roofing contractor. They will easily address the issue with a piece of the leftover felt material and torch it over the defective area.
Some of the signs that you would want to repair or replace the roofing felt include blisters or bumps in the roof, leaks at the flashing and lifting, or badly stuck joints.
To sum up the advantages:
- Low cost for the felt underlayment
- Flame retardant to a degree
- Keeps out the external noise
- Can be installed on any roof shape or size
- Easy to repair
Disadvantages of Traditional Felt Underlayment
Traditional felt underlayment has a disadvantage in that they’re notorious leakers. Sure, they might repair well, but that sure is a good thing because you will need to do regular maintenance on a roof with felt underlayment if you want it to remain in good condition. Felt roofs are known to leak, they’re known to split at the seams, peel, and will suffer water damage far worse if the water pools than with synthetic underlayment.
You may find yourself in need of frequent roof repairs as the roof ages due to the breakdown of the materials. They won’t hold up to weather damage as well as synthetic underlayment will. Felt can also be dangerous when you put it up on the roof. Synthetic underlayment has an extra grip for walking qualities. The felt paper doesn’t have that, which explains why some roofers even refuse to use felt. Remember again, however, that even with synthetic underlayment, some will be more slippery than others. You need to carefully check what type of synthetic underlayment brand you will use.
You also shouldn’t expect your roof to last as long as traditional felt because it just won’t happen in most cases. Especially as the roof ages, you will feel like you need to constantly make minor repairs to the roof. After 20 to 30 years, felt will degrade so much in quality that it will offer next to no water protection. It will tear, it will crumble, and it will fall apart.
Another issue with traditional felt is that shingles can ripple because the felt paper won’t lay completely flat. You may even see somewhat of an uneven shingle pattern after you install the shingles because of the nature of felt. With synthetic underlayment, you don’t encounter this issue quite as much. When the shingles don’t lay right due to felt, they might redo it, but not all roofers will do that. In some cases, you just get stuck with a roof that looks bad.
To sum up the disadvantages of traditional felt, they include:
- More slippery
- Take more rolls to install
- Felt degrades much sooner than the synthetic underlayment
- This can lead to a poor-looking roof
- Requires more repairs as time goes on
- Your roof won’t last as long
Should Your Roof Have Synthetic Underlayment?
We just highlighted some of the advantages and disadvantages of a synthetic underlayment, but in general, we would recommend going with synthetic underlayment if you can afford the extra cost. Your roof will last longer as a result. What we like about it is that it may cost more upfront, but over the long term, a good synthetic underlayment brand will pay for itself because you won’t need to pay as much for repairs.
The synthetic underlayment choice won’t make sense for everyone due to the higher cost. Not everyone has the budget for synthetic underlayment, but with the growing advantages, it is getting harder and harder to justify the use of traditional felt. Especially if synthetic underlayment becomes cheaper, it will likely phase out traditional felt altogether because that’s the biggest reason that people choose it.
Are There Other Roofing Underlayment Alternatives?
The two biggest would be the synthetic underlayment and the felt underlayment, but you do have a third choice. You could choose self-adhered underlayment. This type of underlayment will have a sticky back that you can adhere right to the roof deck. This helps you to create a waterproof seal between the roof deck and the underlayment.
You might use this choice at weak points in the roof where strong winter weather can cause havoc on your roof. Some of the examples where you would use it include:
- Vents
- Eaves
- Skylights
- Chimneys
- Valleys
Conclusion
Hopefully, we have shown you the advantages and disadvantages of each underlayment well enough that you can decide for yourself what kind of roof underlayment you would like to use for your home. Making an investment in your roof will pay dividends over time because the roof will do a better job of keeping the water out. When water penetrates the home’s roof, it can lead to some costly damage. If you’d like to learn more about roof replacement services, please call RGB Construction today at 856-264-9093.
