How tall does a service mast need to be?

The service drop attachment point typically must be at least 12 feet above grade for residential applications, with additional height needed for clearance over driveways or roads per local code.

Can a service mast be attached to the side of the house?

Yes, wall-mounted masts are common. They are bracketed to the exterior wall framing with support straps, and bracing may be required depending on the height and span.

What causes a service mast to lean or bend?

Ice loading on the service drop wires, wind, deteriorated bracing, and corrosion at the base are the most common causes of a leaning service mast.

Does replacing a service mast require a permit?

Yes, service mast work involves the utility connection point and requires a permit, inspection, and coordination with the utility company for a temporary disconnect.

What is the weatherhead on top of the service mast?

The weatherhead is a fitting at the top of the mast that curves downward to prevent rain from entering the conduit while allowing the service entrance conductors to exit and connect to the utility drop.

Service Mast — Overhead Power Entry and Code Clearance

A service mast is a vertical metal conduit that extends above the roofline to support the overhead utility service drop conductors at the required clearance height for safe power delivery to a building.

Service Mast diagram — labeled parts and installation context

What It Is

The service mast is a rigid conduit, usually 2-inch or 2-1/2-inch galvanized steel or aluminum, that rises through or alongside the roof to reach the minimum height required for overhead service drop attachment. A weatherhead at the top keeps rain out of the conduit, and the service entrance conductors run down through the mast to the meter base. NEC Article 230.24 establishes the minimum clearance requirements: the service drop attachment point must be at least 12 feet above finished grade for residential applications, 12 feet above driveways accessible only to passenger vehicles, and 18 feet above public roads.

The mast must be securely braced to handle wind loads and the lateral pull of the service drop cables. The combined tension from the service drop span, ice loading, and wind can exert several hundred pounds of lateral force on the mast. Most utilities require the mast to be braced with a roof bracket, wall bracket, or guy wires when the mast extends more than 3 feet above the roof penetration point.

Types

Through-roof masts penetrate the roof surface and are sealed with a flashing boot or lead flashing that integrates with the surrounding roofing material. This is the most common configuration on residential homes because it provides a straight vertical path for the conduit and keeps the service drop attachment centered over the building. Side-mounted masts are bracketed to the exterior wall with heavy-duty pipe straps and support brackets, and are used when roof penetration is not practical or when the utility attachment point needs to be near a gable end.

Heavy-duty masts with guy wires or diagonal braces are required for longer service drop spans where lateral tension is higher. Material choices include galvanized rigid steel conduit (the most common and most durable), aluminum rigid conduit (lighter but less resistant to bending), and heavy-wall EMT in jurisdictions that permit it. The conduit must be large enough to accommodate the service entrance conductors without exceeding NEC fill requirements, typically 2-inch minimum for 200-amp residential services.

Where It Is Used

Service masts are used on residential and small commercial buildings that receive overhead utility power. They are most common on single-story homes where the eave height of 8 to 10 feet is too low to meet the minimum 12-foot service drop clearance without extending the attachment point above the roof. Two-story homes often meet clearance requirements at the eave and may use a wall-mounted hub fitting instead of a mast.

In areas where utilities provide underground service, the mast is not needed because the service lateral arrives through a below-grade conduit to the meter. However, many older neighborhoods and rural areas still use overhead service drops, making the service mast one of the most visible components of the electrical service entrance.

How to Identify One

Look for a vertical metal pipe rising above the roofline with a curved weatherhead fitting at the top and utility wires attached just below. The mast typically passes through a roof flashing boot on the roof surface or is bracketed to an exterior wall with pipe straps and a support bracket. The service entrance conductors emerge from the weatherhead and loop upward to connect to the utility drop wires.

At the base, the mast transitions into the meter socket through a hub fitting or enters the building wall through a weatherproof penetration. The mast is typically painted gray or left in its natural galvanized finish and is the tallest element projecting from the roof other than a chimney or plumbing vent.

Replacement

Replacement is needed when the mast is leaning due to wind or ice damage, when corrosion has weakened the conduit wall, when the mast is bent from impact, or when roof work has changed the clearance geometry. A permit, utility coordination, and a temporary service disconnect are required for mast replacement because the utility must detach the service drop wires from the weatherhead during the work.

The replacement mast must meet the same conduit size, bracing, and clearance requirements as the original. The roof flashing must be properly integrated with the roofing material to prevent water intrusion, and the weatherhead must be positioned so that the service drop attachment point meets or exceeds the minimum code clearance for the specific location.