Q: I’m re-roofing my barn with metal roofing. I was thinking of extending the roof 18 inches past the walls so dripping water falls farther away from the barn. Right now I’ve got gutters, and I’m tired of them clogging up with leaves and debris. What is the best practice when it comes to gutters or no gutters? What about sizes for both gutters and downspouts? What would you do if you were me?

A: Soil composition is an important thing to consider when it comes to the question of gutters or no gutters.

I grew up in Cincinnati. The soil there is a dense, poorly draining clay deposited by a series of massive continental glaciers that covered the land four times in the past 2 million years.

On the other hand, the soil makeup in New Hampshire, where I now call home, is quite sandy, and it drains well. Most houses and barns there have no gutters. Instead, coarse gravel (mine is the size of walnuts) is placed on top of the soil beneath the drip line of the roof. This is an ingenious method of minimizing splash against a structure from the water that’s running from the roof.

Gutters and downspouts will collect all of that water and pipe it to another location to minimize wetness near a house or barn. They are especially useful if you have a full basement or crawl space. You don’t want to drop thousands of gallons of water onto the soil next to your foundation and then hope it doesn’t seep into the basement. I always advise people who complain of wet basements to pipe roof water away from their homes to the lowest spot on their building lot.

Residential gutters typically come in 5-inch or 6-inch sizes. The 5-inch gutters are the most popular and work for most roofs. The downspouts can help you size the gutters: 2-by-3-inch downspouts fit 5-inch gutters, and 3-by-4-inch downspouts fit 6-inch gutters.


The shape of your house or barn and your preference for where you want downspouts to be should drive your decision about which size is right for you. A single 2-by-3-inch downspout will handle 600 square feet of roof area, while a single 3-by-4-inch downspout will handle 1,200 square feet of roof area.

The downspout should drop into plastic drainpipes that are buried underground. These pipes will carry the water safely away from the house or barn. Check to see if your local jurisdiction requires you to pipe your roof water into a local storm water sewer system or holding pond.

As for the leaves and branches that can clog gutters, micro-mesh gutter guards will keep the debris out. I’ve done gutter guard testing for years and found micro-mesh to be the best system. It’s important for the guards to be installed so their slope matches that of the roofline above them. That way, leaves and other debris will wash off the guards in the rain or be blown off on a windy day.


Tim Carter has worked as a home-improvement professional for more than 30 years. To submit a question or to learn more, visit AsktheBuilder.com.