Why Do Some Gutters Have Slots?

If you are someone who does your own home improvements and home maintenance, you may have noticed when cleaning the gutters or replacing a gutter that they have some slots on the front-facing side. Older gutter styles and certain gutters do not have slots. So why do some gutters have slots, and what purpose do they serve?

Some gutters have slots on the side of the gutter facing away from the house as an overflow protection measure. The slots allow excess water in an overflow scenario to exit from the front of the gutter rather than the side close to the house and potentially causing water damage to the house and roof.

It turns out that the slots on your gutters have an important function. Let’s look at the details, which will come in very handy when doing gutter maintenance.

What Purpose Do Slots In Gutters Serve?

If you take notice, you will observe that not all gutters have slots included in their forward-facing profile. Older homes that have metal gutters typically do not exhibit this feature. The slots in the gutter are a more modern feature that has appeared in the gutters made of molded materials since it is easier to include this feature in their designs.

The slots that are on the front of the gutters are a safety feature that is intended to cater to a gutter that overflows. Should a gutter overflow, for whatever reason, you don’t want the water filling the gutter to the top and overflowing toward the house.

Water overflowing on the house side of the gutter can result in water damage to the roof beams that support the eaves of the house and also to facia boards if they are installed on your house.

The roof beams that support the overhanging eaves are generally protected from the weather by the roof covering that extends over the eaves. The gutter often is secured directly to the end of these beams. If water overflows toward the beams, it will come into contact with the end-grain of the wood. The wood will absorb the water via wicking action and will travel up the beam.

This can be problematic if it occurs on a regular basis, as the wood softens when it gets wet and may no longer be able to support the weight of the roof.

If you reside in a location which has a climate that has high humidity, the wood may take some time to dry out, which could result in mold and wood rot setting in which will destroy the wood beams in the long term.

The slots in the gutter prevent this by giving the water an exit point before it reaches the top of the gutter. This allows the water to exit at the front of the gutter rather than the back, thus protecting your roof, the timber beams, and other roof features from sustaining water damage.

How Do I Prevent My Gutters From Overflowing?

In order to take preventative measures to stop your gutters from overflowing, we first need to examine some of the most common causes that result in an overflowing gutter.

1. Incorrect gutter leveling

The gutters must not be installed perfectly level. They should be fitter so that they have a gentle slope towards the side where the downpipe is located. If the gutter is incorrectly angled, it will cause a buildup of water in the gutter, and it will overflow in a heavy downpour. It will also result in water standing in the gutter, which can become a breeding ground for mosquitoes. To fix this overflow issue, you will need to adjust the slope of the gutters.

2. Incorrectly sized gutter and downpipes

If you live in a location where you have regular heavy rain downpours or snowmelt, then you may need to have wider gutters and down-pipes installed to cater to the additional volume of water that needs to flow through the system.

3. Blocked gutters

Gutters can be blocked by any number of debris, but the most common is from leaves that have fallen from nearby trees during the autumn and wintertime. These leaves build up in the gutter and prevent the free flow of the water through the system. This will require seasonal maintenance to clean out the gutters before the first rains come or trimming the nearby trees so that they do not shed their leaves directly onto your roof.

4. Blocked downpipes

Downpipes have been known to become blocked by many different types of obstructions, from fallen leaves to rodents, birds, and insects making nests inside the downpipe during the dry season. Seasonal maintenance should be done to rid the system of these blockages.

5. Blocked gutter slots

The overflow slots in the gutter can also become blocked, preventing the slots from performing their intended function of directing the overflow away from the house and the roof. The most common cause for this type of blockage of the slots is pine needles, which can slip into the slots and become jammed there and, over time, block the slot completely. Dust buildup can become mud in the event of light rain, which can block the slot when the mud dries. The prevention here would be to trim the offending trees or do spring maintenance on your gutter and clear them out and scrub any dust buildup from the slots with an old toothbrush.

Are Slotted Gutters Necessary?

Slotted gutters are not a necessity for your home. If you size your gutters and downpipes correctly and install them properly, normal gutters without the slots will function just as efficiently.

Many people do not like the aesthetics of the slots in the gutters and prefer not to use this style of gutter because they feel that they detract from the overall look and appeal of their home.

Slotted gutters are also generally more costly than the non-slotted variety, so the price factor is sometimes a deciding factor when people are looking at replacing the gutters on their house.

Slotted gutters are not the only preventative measure available to stop rainwater from overflowing towards the house side of the gutter. There are various types of flashing that can be installed between the gutter and the eaves or the facias that will protect these components should an overflow condition arise.

Often the building code in areas of high rainfall or heavy thunderstorms will have certain stipulations for minimum overflow protection measures that must be included in the type of gutters installed to limit the potential for water damage in the event of a blockage or a particularly heavy rainfall event.


The slots in some types of gutters are a design feature to prevent overflowing water from flowing out over the back of the gutter and towards the house in the event of a blockage in the gutter system. Some people like the feature while others do not like the look of the slots and others feel that it is another place where the gutter can become clogged if it is not regularly cleaned.

If you have many trees over your house that shed their leaves onto your roof in the wintertime, chances are that these leaves will also block the slots on the gutter. Having slots in the gutter, therefore, does not necessarily translate into less seasonal maintenance that you will have to perform on your roof.

The slots may, however, help if you have occasional leaves on your roof that may block a downpipe and cause an overflow.

The choice to have slotted gutters or not is yours, but the housing code in most areas will require that the roof plumbing has some sort of overflow protection. This can be flashing on the house-facing side of the gutter, or gutters with a front face that is lower than the rear face, or gutters with slots.

Slots on a gutter are but one solution for the overflow problem, so do some research into alternatives and decide on what would look better on your house and what would suit your individual needs better.

About Gutter Gorilla

The Gutter Gorilla has been providing superior seamless gutter installationgutter guardsgutter cleaning, and gutter repair services to our clients in CharlestonMount PleasantSummerville, and the surrounding areas for years. Our commitment is to provide quality and timely service without compromise on every job, and we are proud of our high standard of service. If you are looking to protect your residential or commercial building from the harmful effects of water, have us install your gutters. The Gutter Gorilla, one of the market leaders in the industry of seamless gutters installation, gutter guards, and gutter repair.