Roof Gutters

Choosing Rain Gutters: Wood, Metal, or Plastic?

UPDATED 12/27/2011

Bird's-Eye View

Help keep water where it belongs

Roofs shed a surprisingly large volume of rainwater. Gutters can be a nuisance, but they're an important first line of defense in keeping water away from the house and out of the basement.

Gutters are available in a variety of materials, styles, and price ranges, but sizing them correctly is a key consideration.

See below for:
LOOK FOR SOMETHING THAT WILL LAST


Key Materials

Several types of gutter hangers are available

There are two key issues when hanging gutters: how well the hanger and fastener will support the gutter; and how easy the hangers are to install. Options include straps nailed to the roof, hidden brackets with integral screws, snap-lock hangers that are attached to the house before the gutters are installed ,and ribbed aluminum spikes that are driven through the gutter and supported by ferrules.

Snap-lock hangers support the gutter from below as well as above, so they offer more support. That's a factor in snow country, but these hangers also are more time consuming to install.

Hidden hangers are popular with installers. Using integral hex-head screw makes installing these hangers easier, and they're often a first choice with gutter contractors who typically work with K-style aluminum gutters. Hangers can be snapped into place on the ground, so there's less fumbling for tools on the ladder.

Gutters should be attached to rafter (or truss) tails, not just 1x fascia. When roof framing is on 24-inch centers, Rhode Island builder Mike Guertin fastens gutters to each rafter tail. For framing on 16-inch centers, he uses every other rafter tail.


Design Notes

Do you need gutters, and if so, how can they work harder?

Are they necessary? The answer depends on your climate. If you get a lot of rainfall, or you don’t get a lot annually, but when it comes, it all comes at once, then gutters may be essential. Consider other solutions, such as the Frank Lloyd Wrightian rain chain, gravel trenches under the eave line (which also complement a fire-safe zone strategy), or even partial gutters at strategic locations, such as over entryways.

Gutters are often an afterthought —something that's just tacked on at the end of the job. They might still do their job if addressed in this way, but you may be missing some great opportunities.

Gutters are water-collection systems. A gutter's main job is usually collecting and diverting water to prevent problems. Why not use the same system to solve some? Clean water is a resource that is getting harder to come by. Municipal water authorities use a lot of electricity to move and process water. Diverting rainwater into a cistern for reuse instead of into a storm drain can address both of these issues. If you don't have the space or money to install a system for collecting, storing, and processing rain for drinking water, at least consider using simple rain barrels to collect it for irrigation. Stormwater could also be used to directly irrigate a rain garden.


Builder Tips

Gutter positioning is key to functionality and durability

Good installation details can increase the chance that gutters make it through the winter. Snow and ice sliding off a roof can tear off the gutters in just a season or two. Keep the outer edge of the gutter lower than the plane of the roof.

Sloping gutters by 1/16 of an inch per foot will prevent debris from collecting in the bottom. Avoid spikes and furrules and other hangers that prevent natural expansion and contraction. Use expansion joints on runs longer than 40 feet.

Consider running downspouts into rain barrels or cisterns and using the collected water for irrigation.


The Code

The code

Section 801.3 of the IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code. requires gutters and downspouts on structures located in areas where expansive or collapsible soils are known to exist. The section specifies that roof water be discharged at least five feet from the foundation or to an approved drainage system.

OTHER CONSIDERATIONS

Going underground

Gutters can be a maintenance headache and they will certainly need periodic cleaning. Moreover, gutters sometimes clash with ornate trim or other architectural features, tempting some builders to forgo them altogether.

If that's the case, consider an underground gutter. Perforated pipe buried beneath a layer of crushed stone can pick up runoff and divert it safely away from the house.

For more information on this approach, see these three resources:

A GBAGreenBuildingAdvisor.com detail drawing can be found here: Underground Water Barrier Retrofit.

RULE OF THUMB

Sizing gutters

A good rule of thumb is to allow one square inch of downspout cross-section for every 100 square feet of roof area, so a typical 2x3 rectangular downspout can handle approximately 600 square feet of roof area. A 3-inch round downspout can drain approximately 700 square feet of roof area.

THE DEVIL IN THE DETAILS

Water is supposed to run down the roof, into the gutter, and away from the house. As long as the roof is pitched toward the gutter, the first base is covered.

The second point is a little trickier. Water has powerful surface tension that makes it stick to itself. That's why water runs down your arms and drips from your elbow rather than dripping off your hands. Builders have used drip edges to interrupt this surface tension and make the water fall. When you skip the drip edge on a roof, water runs behind the gutter and rots the fascia, soffit, and rafter tails. It also soaks the ground around the foundation.

ABOUT RAIN GUTTERS

Your choice: half-round or ogee

The two most common gutter profiles are half-round and the so-called K-style, which comes with an ogee profile. Contractors who produce seamless gutters with on-site forming machines are most likely to offer the K-style. Half-round gutters are available in lengths of 10 feet and up and assembled on-site. They can be ordered or bought locally in several materials.

Inexpensive aluminum or PVC gutters can look tacky on a well-designed house with handsome exterior trim. Since attractive alternatives like copper are so expensive, omitting gutters entirely may be tempting in some situations. If that's the case, installing a perimeter ground gutter around the house topped with gravel may be an alternative for controlling runoff.

ABOUT TYPES OF GUTTERS

Look for something that will last

Size and cosmetic considerations aside, the chief question is what material to choose. Choices involve durability, cost, aesthetic, and environmental trade-offs. Materials that can be recycled easily are preferable.

Wood
An earth-friendly material, but wood gutters will need more maintenance than other materials and may not last as long as plastic or metal. High-quality cedar, redwood, and Douglas fir are expensive and getting harder to find.

Aluminum

Easy to recycle and can be formed into seamless lengths that don’t leak. Aluminum also is corrosion resistant. Limited style choices are one drawback.

Steel

Strong and dent resistant. For rust protection, steel gutters can be galvanized with zinc, coated with Galvalume (zinc and aluminum), or terne (tin and lead). Simple galvanized gutters are relatively inexpensive and long-wearing, and can be recycled.

Copper

Elegant-looking, durable, easy to recycle, and very expensive. Sections can be soldered together for leakproof installations or made from coil stock into seamless gutters. Unfortunately, rainwater can leach copper from roofs and gutters and carry it into local waterways, where it may harm to aquatic creatures. It's not known how much copper as a green material in a residential gutter and downspout system actually contributes to the environment, but copper leachate is a consideration.

Plastic

Light, durable, and won’t rust. Sections up to 10 feet long must be joined with gaskets or cement, and the connections are prone to leaking. PVC also has some environmental disadvantages, including low recyclability and toxic emissions during manufacture and when incinerated.


Image Credits:

  1. Dan Thornton/Fine Homebuilding #177
  2. Andy Engel/Fine Homebuilding #125
  3. Charles Bickford/Fine Homebuilding #187
  4. Dan Thornton/Fine Homebuilding #125
Tags: , , , , , ,
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!