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Are Gutters Required By Code (Plain English Explanation)

A gutter and a downspout are essential to prevent long-term damage to the roof of your home and the foundations below. Many people choose to forgo gutters on their homes, and they often do so for the house’s aesthetics.

While gutters are not a requirement by law, the International Residential Code (IRC) defines the installation of and acceptable materials required for approved guttering on buildings and houses. In addition, local codes should always be observed when installing gutters.

Gutters aren’t an IRC requirement, but the code regulates construction. Gutters must be watertight. Choise of gutter material should be considered if rainwater is being recycled. Gutter/downspout slope must be over 1/8” per ft and terminate at designated collection spot. Systems must be inspected and accessible. Local codes may add more rules.

Gutters Regulated But Not Required By The IRC

Gutters are not a code requirement, but the IRC does regulate the guttering systems that are installed.

Gutter Materials

IRC P2912.5 states that the materials used for the construction of gutters and downspouts should be compatible with the end-use of the water.

In other words, if you are collecting rainwater in storage tanks for use in your garden, then the gutter material should not contaminate the water in any way.

This regulation also stipulates that all gutter and downspout joints should be watertight. Complying with this part of the rule is easy; who would want a leaking gutter system?

Gutter/Downspout Slopes

  • The slope of gutters and downspouts along the length should be not less than 1/8″ per ft (10.4 mm/m) (P2912.5.1).
  • All gutters, leaders, and rainwater collection pipes must slope towards the collection points (P2912.5.1).
    • Gutters and downspouts should be positioned to allow water to flow freely and to prevent water from collecting at any point other than those designated for this purpose (P2912.5.1).

The slope of the gutter and downspout is regulated because channeling water away from the house foundations is crucial to structural integrity and damp prevention.

gutter and downspout slope measurements along the roof length


  • All pipes, downspouts, filters, and flushes must be easily accessible for cleaning and maintenance (P2912.5.2).

Accessibility for maintenance is important because a clogged gutter is noisy and ineffective.

Gutters and Sidewall Flashing

Gutters can also be used in conjunction with sidewall flashing (installed where a roof abuts a wall that extends up past that portion of the roof). The purpose of guttering here is to improve drainage.

You can find this regulation in IRC R905.2.8.3, which discusses the requirements for sidewall flashing (we will only look at the part pertaining to gutters):

  • When installing base or step flashing against a vertical sidewall, the flashing shall be unbroken and should be no less than 4″ (102 mm) in height and 4″ (102 mm) in width. The flashing should safely channel rainwater onto the roof or into the gutter and away from the roof.

Gutters Have To Be Inspected And Tested

IRC P2912.15.1 discusses the regulations on inspecting and testing the roof gutters. All gutters and downspouts should be inspected and tested to confirm that they are compliant with the code and therefore effective to perform their function.

This section of the regulation states:

  • An inspection is necessary to confirm the installation and angle of the slope in accordance with the regulation.
  • During the inspection, 1 gallon (3.8 L) of water shall be poured down each gutter opposite the collection point to test the slope and angle of the gutters.
  • The gutter should not leak while water is poured down it, nor should any water pool or collect in the pipes.

Consult Your Local Codes For Additional/Amendments

While the IRC stipulates the internationally recognized building regulations, most local authorities have codes applicable to their areas. These codes are designed to regulate the local industries according to local laws, climates, and specific factors in the location.

These local codes do supersede the IRC but are designed always to be used in conjunction with the IRC regulations and any other code specific to the industry.

Let’s look at two examples of where local codes have additional/amended guttering requirements: Illinois and Wyoming.

Illinois and Wyoming: Further Gutter Requirements

Although Illinois and Wyoming do have to comply with IRC codes, they also have local building codes that they need to comply with.

Section 1502.4 of both the Illinois and the Wyoming building codes state that all gutters and leaders other than Group R-3 (private garages and buildings of Type V construction) shall be a Schedule 40 plastic pipe or fireproof material when installed on the outside of any building.

Section 1503.2.1 further states:

  • Flashing should be installed at gutters, wall and roof intersections, and wherever the roof slope changes direction, as well as around all roof openings.
  • If the flashing is constructed from a metal material, the metal should be corrosion resistant and 0.019″ (0.483 mm) thick. (No 26 galvanized sheet).

Are Gutters Required By Code In The UK?

The UK has a fairly extensive Building Code. Section H3 defines the code and requirements for rainwater drainage as follows:

  1. Acceptable provision shall be made for rainwater to be channeled away from the roof of a building or paved areas by an adequate drainage system.
  2. The system must distributes rainwater into the ground without damaging any building or adjacent structure.
  3. The regulations state that rainwater or surface water should not flow into a septic tank or cesspool.
  4. A rainwater drainage system is defined as:
  • An adequate outfall system to carry rainwater from the roof to a soakaway, a watercourse, surface water, or combined sewer.
  • An outfall system that prevents the risk of leakage and blockages and is accessible for clearing blockages and maintenance.

Gutters would fulfill all of these functions and requirements.

Section 1 of H3 (pages 40-42) defines the regulations for gutters and rainwater pipes in detail. Unfortunately, I cannot link to the specific sections of the code, so the following table included page numbers to make navigation as easy as possible.

SubsectionPage NumberPointsBrief description/explanation
Rainfall intensity401.1 and 1.2Gutter design is influenced by rainfall intensity.
These points cover the rules that apply to rainfall intensity according to the different zones (which are set out in Diagram 1 on page 42).
Valley and parapet gutters are specifically mentioned.
Obviously, gutters in high-rainfall zones will need to be capable of channeling vast amounts of water.
BS EN 12056 should be consulted and applied in accordance with this regulation.
Gutters40-411.3-1.7Gutter design is influenced by the surface area that needs to be drained as well as the pitch of the roof.
These points go through the rules regarding gutter and outlet sizes.
Tables are provided for the calculation of drained area and gutter and outlet sizes.
Rainwater pipes41-421.8-1.10These points govern the rainwater pipes to which the gutters connect, including where they should discharge and how big they should be.
Materials for gutters421.16This point describes the approved materials and the regulations regarding the strength and durability of the materials. Gutters should be watertight and well-supported (without compromising the material’s ability to adjust to thermal input). Non-metallic material must be used to separate different metals to prevent corrosion from electrolysis.

Reasons to Install Gutters

Gutters can add to the home’s aesthetic or significantly detract from it (this is possible one reason why so many beach houses don’t have gutters). However, you should not make your decision to install gutters based on how they look; gutters (and downspouts) have an essential job to do!

Gutters and downspouts channel the flow of rainwater away from your home, protecting your roof, eaves, and the foundations of your home. They are obviously more important in some regions than others, but I would say that most homes could benefit from the installation of a guttering system, especially those with a flat roof design.

Gutter and downspout systems protect your home from water and rain damage by:

  • Diverting rainwater away from your garden.
  • Preventing soil erosion around the foundation of your home.
  • Preventing cracked and damaged foundations.
  • Keeping your basement from flooding.
  • Protecting the paintwork on your home.
  • Preventing water stains on the exterior walls and fascia boards.
  • Halting the growth of mold and mildew on your eaves and facia boards.
  • Blocking rainwater from dripping off your roof and entering your home through windows and doors.
  • Gutters can add to the charm of your home.

Arguments Against Gutters

Sometimes gutters do have their downside and are not a welcome addition to a house or building. While many modern homes are built without them, many people are removing their existing gutters from their homes for the following reasons:

  • Gutters can be expensive to install, clean, and maintain.
  • Branches, leaves, and other debris collect in the gutters, clogging them up.
  • Debris in the gutters can become heavy, causing the gutters to break and the brackets to become loose from the walls.
  • In cooler climates, water can freeze in the gutters causing damage to the gutters and exterior walls.
  • Gutters can be noisy! Water can trickle through the pipes causing constant dripping sounds, or the wind can blow against the gutters dislodging them and making them swing back and forth, grating against the walls and pipes.
  • Gutters do not always fit in with the style of the building.

A Quick Note On The International Plumbing Code

Chapter 11 of the IPC defines the regulations regarding sizing methods for gutter and piping systems that channel the water away from a building and stipulates the regulations regarding piping materials and subsoil drainage systems.

However, in Chapter 1 [A] 101.2 of the IPC, we can see that this code does not apply to detached one- and two-family dwellings or multiple single-family dwellings (townhouses) with no more than three stories and with a separate entrance. These must comply with the IRC.


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