Snow guards and retention hold snow on a metal roof so it does not slide off over doors, walkways and parked vehicles.
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Snow guards and snow retention are devices fixed to a metal roof to hold snow in place, so it melts off gradually instead of sliding in a single slab. They matter most over doorways, walkways, gas meters and parked vehicles. A technician places them along the eave and across the slope where the snow would otherwise release.
A metal roof is built to shed snow. The same smooth surface that lets snow slide also lets it leave the roof all at once, in a slab that can weigh a great deal and that lands wherever the slope points.
The hazard is particular to metal. Public filings describing snow-retention devices note that sliding snow and ice from metal roofs can be hazardous to people, to the landscape, to property and to building components.
A local roofer can look at where the snow would fall and suggest where the retention should go. The phone line at (833) 751-2102 is answered around the clock.
Do not walk on a metal roof in snow or ice to check the retention, and do not stand under a slope while snow is sliding off it. Never try to knock a slab loose with a shovel or pole from below, because a partially loose slab can release all at once. Keep vehicles and pets clear of the drop zone during a thaw, and mark the area below the roof with a cone if you cannot move the car. Call a roofer to adjust or repair the retention, because a device left loose can fall onto someone below.
A single row of guards along the eave holds the snow nearest the edge, so the slab that does form cannot slide off the roof in one piece. This is the basic layout for a metal roof above a walkway or a driveway. It works best on a moderate slope with steady snowfall, and it is usually the first row a technician installs when space is tight.
On a long metal slope, several rows of guards are spaced up the roof so that the snow is held in stages rather than in one mass. This suits a house with a long run of standing-seam roof and a path or parked car below. The rows are set so that the lower ones take the first load and the upper ones catch what moves down from above.
A doorway or an entry is the single most important place for retention, because a slab landing on a person is the outcome to prevent. The layout here is closer and tighter, and the device is often combined with a short section of rail that breaks the slide. This type applies to any entry below a metal slope, including a porch, a shed door or a gas meter on the wall below the roof.
Tell us what's happening and we'll tell you honestly whether it's a quick fix, and what snow guards and snow retention should cost.
A metal roof has a smooth, low-friction surface that lets snow slide once the bond with the melt water breaks. Asphalt shingles are a different surface, and they can still release snow on steep slopes. Snow retention exists to put back the friction a metal roof lacks.
Snow sits on a roof because the surface grips it. When a thin layer of meltwater forms at the interface with the roof, the snow can slide. A slab that starts moving can carry the whole depth of the snow above it.
Snow guards should go along the eave and across the slope wherever the snow would land on a door, walkway, gas meter or vehicle. Drifting at valleys, parapets and roof offsets also concentrates snow, so those places need attention even when they are not above a path. The layout is set by what sits below the roof, not by the roof alone.
Moscow's building code notes that snow builds up at valleys, parapets and roof offsets, and that designers should consider that build-up. Those are the places where two roof planes meet, which is where additions, dormers and porches tend to sit.
The price depends on the length and pitch of the roof, the number of rows needed, the metal profile and the seam type, and how the device can be attached without piercing the seam. Access, the height of the eave, and any work needed to repair the roof edge also change the cost. The price is explained and approved before work starts.
A long roof with several rows takes more devices and more time than a short one with a single row over a door. The profile and seam matter because some styles need a different attachment, and a technician may need to adjust the approach for each panel type.
Snow retention controls how snow leaves the roof, but it does not change how much snow melts on the roof in the first place. Heat from a poorly insulated attic can melt snow from underneath, and the meltwater can then refreeze at the eave. The attic and the retention are often addressed in the same plan.
A dam at the eave is a separate problem from a slab sliding off the slope, and both can happen on the same roof.
Remaining life is judged on the roof and the devices themselves, not on a fixed number of years. Look at the fasteners for loosening or rust, the seal around each attachment, and any bending or cracking in the device. A technician can check all of these after a winter and tell you whether anything needs attention.
Check the retention after each winter, from the ground with binoculars or a camera if you cannot reach it safely. Look for devices that have tipped, rails that have bent, and fasteners that have pulled out of the panel.
The technician starts with the slope and the building around it. The question is where a slab would land if it released from the upper roof, which means looking at doors, walkways, gas meters, parking areas and the drop from the eave. Those are the zones that need holding, and the rest of the roof may need only a light layout.
Snow guards come in several styles, and the right one depends on the metal profile, the seam and the attachment the roof can take. A standing-seam roof is different from a corrugated panel, and the attachment must avoid piercing the seam in a way that will leak. The technician confirms the choice against the roof itself rather than a catalog, because a device that fits one panel style can fail on another.
Snow guards are placed in rows across the slope, with the lowest row at the eave and the upper rows spaced to hold the snow above them. The layout depends on how much snow the slope will carry and how the snow drifts, so the technician checks the valleys and the roof offsets where drifting concentrates load. The layout is agreed on before anything is attached.
Each device is fixed with the fasteners the roof system specifies, and fasteners are kept out of the seam where water could enter. The attachment points are sealed to the roof's own detail rather than with a generic sealant, because sealant ages differently from metal. The crew cleans up the cuttings and metal shavings, which can rust and mark the finish if left on the roof.
After the first real snowfall and thaw, the roof is checked to see how the snow is holding. Any section that still releases in a slab is noted, and the layout is adjusted if needed. This check is worth scheduling because the first storm shows where the drifts really form, which is not always where the layout expected them.
Moscow is a town of hills, with houses set on slopes where a truck and a dumpster may not reach the front door.
The Palouse gets snow that sits on a roof, thaws and refreezes, and that cycle is what makes a metal slope so unpredictable. A slab may release on a mild day after a cold week, or it may hold through a warm spell because it is frozen to the panel.
Pullman is a separate city in Washington, with its own permit system and its own design criteria, and the rules for work there are not the same as Moscow's.
Not sure if you're covered? Check your ZIP code.
Metal roof repair and installation, planned around how the panels shed snow onto doors, walks and parked cars.
How snow weight, drifting and roof shape affect a Palouse roof, and who confirms the design figure for an address.
Stopping eave ice dams on Palouse roofs through attic insulation, air sealing and ventilation, and safe removal when water is already getting in.
Gutter repair and new runs, planned so meltwater leaves the eave instead of freezing at it.
Design snow load is the weight a building code tells a designer to plan a roof for.
A metal roof suits a Palouse winter because its smooth surface lets snow slide off rather than build up.
No device stops all snow movement. Snow guards hold the snow in place and break the slab into smaller pieces that release more gradually. A slab can still move in an extreme thaw or where drifting builds a large load. The layout is made to reduce the risk over the places that matter most, such as doors and walkways.
In most cases yes, provided the roof panel and the seam can take an attachment without being damaged. A technician checks the profile first, because some devices suit only certain panel styles. The attachment must avoid piercing the seam in a way that could let water in. Ask for the layout to be explained before any fasteners go into the roof.
Snow guards can fail when the load is greater than the layout was designed for, when the fasteners were not set well, or when a slab has been pushed against a rail until it breaks. A failure after a storm is a sign that the layout needs to be checked, not that the device should be abandoned. Call the line to have the roof looked at after the next thaw.
Asphalt shingles hold snow better than metal, but they can still release it on steep slopes or after a thaw. The need depends on the pitch, the snow load on the roof and what sits below. A technician will look at the roof and the entries and say whether retention is worth adding. Snow retention on asphalt is a judgment call, not a fixed rule.
The building code sets a design snow load for each address, and the city or county building official confirms it. Moscow's code addresses drifting and snow build-up at valleys, parapets and roof offsets. Pullman publishes its own criteria, and the two cities do not use the same figures. Ask the building department which criteria apply to your address before you choose a layout.
The first real snow and thaw after installation is the best time to check. That is when the drifts form where they actually will, which can differ from where the layout expected them. A technician can come back after that first winter to adjust the rows. Ask for the check to be booked when the work is agreed, so it is not forgotten.