Non Penetrating Roof Mount Guide

Flat and low-slope roofs on apartments, offices and commercial buildings rarely welcome a drill. A non penetrating roof mount solves that by holding the mast with weight instead of fasteners, so the membrane stays intact. It also moves the risk from leaks to wind, roof load and the roof owner’s warranty. This guide covers how a ballast mount works, what decides the ballast, and the checks to make before one goes up.

How a non penetrating roof mount works

The mount is a sled: a square or cross-shaped steel base with trays or rails that hold standard concrete blocks, and a mast socket or clamps at the centre. The mast carries the antenna, and the base relies on the weight of the blocks to resist being tipped or slid.

Because nothing is fastened, the whole assembly is a gravity support. That suits roofs where any penetration means a call to the roofer, and it makes the mount easy to move later. It also means the base, the blocks and the pads are the only things holding the antenna in place.

Ballast roof mount for antenna: where the weight figure comes from

The ballast a ballast roof mount for antenna needs depends on the antenna’s size and wind area, the mast height above the base and the exposure of the site. That is engineering, not a rule of thumb, so the number to use is the one in the mount maker’s instructions for that load. Some makers state that ballast for a given site should be set by a local professional engineer.

• Use only the block size and count the instructions specify, set in the trays as shown.
• Do not add antennas, a rotor or extra mast beyond what the instructions cover.
• Where the instructions give more ballast for higher wind exposure, use that figure.

Ballast is dead load on the roof deck. FEMA’s fact sheet on communication towers, masts and antennas says to evaluate the building to make sure it can support the additional loads, so ask the owner whether the roof was designed for equipment at that spot.

Wind exposure: how ballast mounts fail

The same FEMA fact sheet is direct about the weak point. It states that antennas on rooftop masts often use only ballast to hold them in place, which quickly can become dislodged during strong winds. It explains the mechanism too: wind uplift on the antenna can rotate the mast and knock ballast off the sled.

FEMA also notes that building codes require antenna supports to be designed for wind forces based on location, exposure and other factors. A flat roof antenna mount on a tall building, near the roof edge or on open ground sees more wind than one in a sheltered courtyard.

• Set the base back from the roof edge where the instructions allow, with its fall zone clear of the edge.
• Keep the mast as short as the reception survey permits; our guide on how high to mount a TV antenna covers the height question.
• FEMA says guy wires or bracing can improve mast performance in high winds; the trade-offs are in guyed vs self-supporting towers.
• Inspect the blocks and the mast after major storms, as FEMA recommends a regular inspection and maintenance plan.

Protecting the roof membrane

The point of going non penetrating is lost if the frame wears through the roof. Steel feet and concrete blocks are abrasive, and the frame moves slightly with wind and temperature. FEMA’s fact sheet also shows how a collapsed rooftop mast can puncture and peel a membrane, so stability and protection go together.

• Set the frame on the protection pads or mat the mount maker supplies or specifies, never directly on the membrane.
• Use pad material the roofing manufacturer accepts for that membrane.
• Keep the base off drains and out of low spots where water ponds.
• Route the coax so it does not drag over the roof surface or block drainage, and protect any traffic path to the mount.

Use galvanized or stainless hardware. FEMA notes that dissimilar metals in direct contact can cause galvanic corrosion.

Roof owner, warranty and permission

Get written approval before any equipment goes on a commercial or multi-unit roof. The owner or property manager decides where equipment may sit, and the roofing manufacturer’s warranty terms often control what can rest on the membrane and what must go under it.

1. Ask who holds the roof warranty and request its rooftop equipment requirements.
2. Confirm the location, the pad material and the access route with the owner.
3. Photograph the roof surface before and after the install.
4. Leave the mount maker’s instructions and ballast figure with the owner.

Tenants and condo owners have narrower rights on shared roofs. The FCC’s reception device rule, summarised in our roof tripod vs antenna mast guide, applies only to areas the viewer owns or has exclusive use of.

Non penetrating mount vs tripod vs wall mount

A ballast base is one of several ways to stand a mast on a building. The table compares the common options for a roof job.

On pitched roofs a tripod is usually the better choice; the roof tripods category lists 3, 5 and 10 foot tripods supplied for lagging into the framing. FEMA notes that on high-wind sites a ballast sled can be replaced with a structural frame connected to the building, after a structural engineer has evaluated the roof.

Grounding still applies

Sitting on blocks does not exempt the mast from bonding. A ballast mount puts a metal mast high on the building, and the mast and the coax shield need the same grounding as on a tripod or wall mount.

Plan the grounding conductor route before the mount goes up, keeping it off the membrane with supports the roofer accepts. The conductor sizes, the grounding block and the bonding point are covered in how to ground a TV antenna and mast.

Where to find mast and mounting hardware

The antenna mast category lists mast sections and the antenna mounts category lists wall and universal mounts, all in the antenna, tower and satellite division with tripods and towers. To ask about a non penetrating base for a specific job, contact your sales representative through the Bursma contact page, or apply for a Bursma dealer account.

Frequently asked questions