Leaves and twigs aren’t the only things that get trapped in your home’s rain gutters. Often times, water doesn’t drain out because of the most unexpected reasons. So if you’ve been mystified by the amount of clogs you’ve been getting every year, this list may explain what’s happening to your house’s gutter system.

Poorly made downspouts

Gutters are meant to catch and help direct water via downspouts away from your homes foundation. But they also catch things that fall out of the sky and roll down your roof. Poorly designed and sized downspouts may cause a blockage of this debris, forcing the water to stop flowing freely and dam up in the gutters. If the exit to the gutter remains open there most likely won’t be a clog.

Typically downspouts are size 2 inch x 3 inch with is a very small opening to fit even a small handful of leaves through. A better choice is to use 3 x 4 size which is twice the area of 2 x 3. This will help your gutters tremendously by allowing debris to flush out of the downspout and keep them from overflowing due to a clog.

You should also pay attention to where you place your downspouts and how many of them you need on a section of gutter. Otherwise, you won’t just be dealing with clogs but also overflows and the erosion it can cause too. General guidelines suggest a 30-40 feet section of gutter or 400 square feet of roof should be the maximum for a single downspout. Roof style and design is another factor to consider. Valleys funnel a lot of water, especially under hard rains and can overwhelm a single downspout. If this is the case you need to have your gutters pitched in two directions to split the amount of water into multiple downspout drains.

Bad gutter design old k gutter pitched poorly

If the downspout isn’t the problem it could be the entire gutter. If you’ve had clogging problems all-year round, then chances are, a low quality gutter system is to blame.

Replace your home’s gutters with something that you won’t have to constantly worry about. When buying, focus on the following factors:

  • What it’s made of. Thick aluminum stock is strong and rust-proof, so most homeowners prefer to use gutters constructed from them.
  • How durable it is. Plastic and galvanized steel gutters don’t last as long.
  • What kind of debris it can handle. Open gutters can’t handle most debris while two-piece systems with gutter covers are usually weak against specific debris . Read more about it here.
  • How wide it is. Residential gutters come in two sizes, 5 and 6 inches. Larger sizes are available for commercial sized roofs.
  • How it’s installed. To make sure that gutters function properly, they need to be sloped toward each downspout.  This may range from ¼ to ½ inch for every 10 feet of gutter. Other factors affect this such as unlevel fascia or roof lines, awnings, desired location of the downspout and other architectural details.
  • How much maintenance it needs. All open K gutters under some sort of tree need maintenance over the years.  Seamed gutters will require more attention due to more joints and potential for leaks. Gutter protection options eventually need service as well as weather takes its toll causing gaps to form at seams.  One-piece seamless cover systems don’t need any maintenance at all.

A decaying roof worn out roof shingles

Knowing what clogs gutters means knowing that the roof itself can be part of the problem. Our roofs protect our house from almost everything mother nature can throw at us. But when they start to break down, they may take the gutters with them. A decaying roof can send broken parts of shingles and other materials into your gutters. This kind of heavy debris can’t get cleared up by running water, so it causes difficult clogs.

Growing plants

One particularly annoying problem with gutters is plants growing inside them. Seeds carried by birds and the wind can slip into these ducts and feed on the water and soil nutrients that flows down from the roof. The result is an accumulation of growing plants that have taken roots on top of the house. If they’re not plucked out immediately, they could spread and irreversibly damage the gutters.


Homes that use filter style gutter guards may experience trapped pollen on top of the fine mesh. Though this isn’t an entirely grave threat for the gutters, forgetting to clean them may cause the mesh to fail. This prevents water from entering the gutter rendering them useless to keep water away from your home’s foundation.


Of course, this list won’t be complete without snow. Heavy snow can greatly enhance ice formation. When the attic becomes warm enough to melt the bottom layer of the snow on the roof the melted snow then trickles down to the roof’s edge. What clogs gutters is that this melted snow refreezes in the cold gutter and eventually overflows creating hanging icicles. If the weather conditions persist the build up can create a mound that becomes an ice dam which will restrict water from overflowing the gutter and back up the roof. Without the proper protection under your shingles water could leak into the house.

Debris from trees

Aside from the usual leaves and twigs, debris falling from trees can be pine straw, fruits, flowers, seeds, nuts and even an old bird’s nest. Trees are the most common cause of gutter clogs. If they’re not pruned and maintained regularly, they could eventually damage your home’s gutters.

And sometimes it’s just something weird

Maybe it’s none of the above, but if water is overflowing something is wrong. On a brand new gutter it’s possible the drop for the downspout wasn’t cut open. If it’s been working for years or things were cleared out recently it could be some other obstruction like a ball, frisbee, action figure or other toy the kids lost while playing. We’ve found birds building nests in gutters, squirrels hiding nuts, and even a 10 feet long black snake!