Underlayment Options for Asphalt Roofs

[DarkKnight]

Hey everyone!

How effective are different underlayment types, like synthetic versus felt, at preventing moisture intrusion under asphalt shingles, especially in areas with frequent wind-driven rain?

[Alpha]

Both synthetic and felt underlayments can help with moisture protection, but synthetic usually does a better job, especially in areas with a lot of wind-driven rain. It’s more durable, resists tearing, and sheds water more effectively. It also stays more stable over time, even if the shingles aren’t installed right away.

Felt, especially the heavier #30 type, can still be useful, but it’s more prone to wrinkling and doesn’t hold up as well if it gets wet. For harsher weather conditions, synthetic is generally the better and more reliable choice.

[DarkKnight]

Thanks! Do you still need ice and water shield if you’re already using a high-quality synthetic underlayment?

[Alpha]

Even if you're using a high-quality synthetic underlayment, it's still a good idea to use ice and water shield in certain areas. The synthetic layer does a great job overall, but ice and water shield adds an extra layer of protection where it’s really needed, like along the eaves, in valleys, and around things like chimneys or vents.

What makes ice and water shield different is that it's self-adhesive and actually seals around nails. That helps prevent water from sneaking in, especially during heavy rain, snow, or if ice dams form. So using both together gives you a much better shot at keeping moisture out in the long run, especially in tricky spots.

[DarkKnight]

Also, are there any brands of synthetic underlayment that work better with certain shingle types, or are they mostly interchangeable?

[Alpha]

Most synthetic underlayments are pretty interchangeable and work well under all major asphalt shingle brands, but there are a few things worth keeping in mind.

Some roofing manufacturers actually require or recommend specific underlayments to maintain their full warranty coverage. For example, if you're using shingles from a certain brand, they might suggest pairing them with their own underlayment line to keep everything under the same system warranty. So it's a good idea to check the shingle manufacturer's installation guide or warranty details just to be safe.

Aside from that, some premium synthetic underlayments offer extra features like higher temperature resistance, slip resistance, or better UV protection if the shingles aren’t going on right away. That can be especially helpful in hot climates or if your roof might be exposed for a few days before completion.

But in general, as long as you're using a quality synthetic underlayment rated for roofing use, you should be fine with most asphalt shingles.

[DarkKnight]

Is there a limit to how long synthetic underlayment can stay exposed before shingles are installed?