Metal Building Gutters Explained: Interior vs. Exterior and the Smart Choice Today

When you think about protecting a metal building, gutters probably aren’t the first thing that come to mind. But they should be. A well-designed gutter system is one of the most important safeguards against leaks, foundation issues, and costly repairs. Gutters manage rainwater and snowmelt, keeping water away from your roof, walls, and foundation — where it can cause the most damage.

In steel building construction, there are two main gutter approaches: interior gutters and exterior gutters. Older designs often relied on interior drainage, while today’s Butler® buildings and most modern metal structures favor exterior systems for their durability and ease of maintenance.

Let’s break down the differences, their pros and cons, and why exterior gutters are now considered the gold standard.

Interior Gutters: The Legacy Approach

Also called valley gutters, interior gutters are channels built inside the roofline, usually at low points where two slopes meet. Instead of being attached along the roof edge, they are recessed within the building and connected to underground drains or internal downspouts.

Advantages:

• Hidden design keeps rooflines clean

• Useful in unique architectural layouts that require drainage within the footprint

Drawbacks:

• Hard to access for inspection and cleaning

• Higher risk of clogging, ice dams, and overflows since debris is trapped inside

• Leaks often go unnoticed, leading to wet insulation, interior damage, or mold

• Repairs are costly and invasive, often requiring roof panels or liner systems to be opened up

Because of these challenges, interior gutters are considered legacy systems. They are mostly found in older buildings or in specific architectural projects where drainage must be concealed.

Exterior Gutters: The Modern Standard

Exterior gutters are mounted along the roof eaves, directing water into downspouts on the outside of the building. They are now the preferred option for new Butler buildings and for retrofit projects. Butler manufactures fully engineered gutter and downspout systems designed to integrate seamlessly with its roof panels — including the MR-24® standing seam roof system and the Butlerib® II roof system.

Advantages:

• Easy access for inspection, cleaning, and repairs

• Lower risk of hidden leaks and interior damage

• Cost-effective installation and replacement

• Compatible with snow guards, splash blocks, and underground drainage piping

• Standardized Butler® parts (support brackets, drip edges, downspouts) make maintenance simple

• Built from Galvalume® steel with a Butler-Cote™ finish, which provides decades of protection against rust, fading, and chalking

Drawbacks:

• Exposed to the elements (though finishes like Butler-Cote™ are tested and backed by a 25-year warranty)

• Visible on the exterior, though aesthetics are rarely a concern for industrial or commercial buildings

In practice, these drawbacks are minor compared to the benefits. That’s why exterior gutters are the default system in all modern Butler designs.

Interior vs. Exterior Gutters: Side-by-Side

When Should You Use Each?

• Interior Gutters: Only when they already exist in an older building. If you own a steel building with interior gutters, consider a proactive retrofit. Butler Builders can convert interior drainage to exterior systems during a reroof project, eliminating the risk of hidden leaks.

• Exterior Gutters: The clear choice for new construction, reroofs, and retrofits. They provide the most cost-effective, durable, and maintenance-friendly option.

FAQs

Do Butler buildings still use interior gutters?
No. New Butler buildings use exterior gutter systems. Interior gutters are legacy systems mainly found in older designs.

Can I retrofit interior gutters to exterior?
Yes. During reroofing or retrofit projects, Butler Builders often recommend converting interior gutters to exterior systems to reduce risk and simplify upkeep.

How long do exterior gutters last?
With Butler’s Galvalume steel construction and Butler-Cote finish, exterior gutters can last decades with minimal maintenance.

The Bottom Line

Interior gutters may appear in older buildings, but they bring higher risk, more maintenance, and bigger repair costs. Exterior gutters, on the other hand, are:

• Engineered for durability

• Easy to clean and maintain

• Seamlessly integrated with Butler’s roof and wall systems

• Backed by decades of proven performance

👉 If you’re maintaining or upgrading your building, exterior gutters are the gold standard. They not only protect your investment but also make future maintenance simpler and more affordable.

We offer the full line of Butler® gutter and downspout accessories, so if you don't see the part you need for your Butler building, contact us! We can get it.