Installing the first snow guard (C) Daniel FriedmanGlue-On Roof Snow Guards
How to install adhesive snow guards on smooth-surfaced roofs
     


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Glue-on roof snow brakes & snow guards: this article describes the steps in a successful glue-on type snow brake system for smooth surfaced roofing, using a metal roof as an example. Adhesive-bonded snow brakes are used on a variety of smooth surfaced roofs besides metal, including glass, plastic, and some other roof covering materials. We explain why some glue-on roof snow guards fail - being pushed off of the roof by snow loads, and we describe how to make sure the glue-on snow guards will work on your roof.

This article series illustrates types of snow guards or snow brakes or other snow retention devices used on metal, rubber, asphalt, and slate roofs and we explain and illustrate in photographs just how and where these devices are attached to building roofs. We give the reasons for snow & ice retainer use and their history.

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How to Install Glue-Down Snow Guards on a Metal, Glass, or other Smooth-Surfaced Roof

Snow guards at work on a metal roof, Vassar College (C) 2013 Daniel FriedmanWe agree with opinions encountered among roofers that it's better to glue snow guards to a metal roof (or use device that clamp to the standing seam) for two reasons:

  1. Leaks: Even though some snow guards are sold with pre-drilled holes for mechanical fastening of the retaining device to the roof surface, every nail or screw is another hole in the roof, and another potential leak.
  2. Thermal damage: Mechanically bonding a flat-bottomed snow guard to a metal roof may result in roof damage, tearing, leaks, connector hole elongation during wide temperature swings on the roof.

    Thermal expansion differences between the snow guard itself and the metal roof surface may be substantial. Superbond's SB-190, in contrast, can tolerate significant thermal change without damage.

Steps in Gluing Snow Guards to a Roof Surface

Plastic snow guard from Gerber (C) Daniel FriedmanBecause of the problem of poor adhesion of the snow guard to the roof that later come loose or creep down the metal roof, manufacturers offer tips for a successful installation including:

  • Choose & buy enough snow guards before starting the job. Measure the roof dimensions and pitch, then consult SNOW GUARD SPACING & PATTERN to determine how many you will need. Choose a type and size of snow guard that will work with your roof area, pitch and the connection method you've selected.

    In this example we're using Berger's clear surface mount snow guard that's got a large surface and enough thickness that we don't expect the guard to break in use.

    I know, it's not rocket science, but having inspected a number of snow guard installations that have failed by bending, breaking, sliding off the roof, or simply being inadequate to resist the quantity and loads of snow involved, it makes sense to stop and think a minute rather than just gluing any-old-thing up on the roof on a hope and a prayer.

    We bought 30 snow guards to permit two per "bay" in staggered rows between the standing seams of the metal roof being addressed. On a larger or steeper roof we'd have needed more snow guards in more than one set.
SureBond SB-190 Everseal adhesive sealant recommended by our snow guard manufacturer (C) Daniel Friedman
  • Snow guard adhesive choice & adhesive use procedure: For attaching plastic snow retention clips or guards Berger's catalog recommends use of Surebond's SB-190 Everseal adhesive sealant.

    We purchased our snow guards and adhesive sealant from a local roofing supplier, working with ABC Supply Co. Inc., in Poughkeepsie, NY. (SNOW GUARD PRODUCT SOURCES)

    This product will bond permanently to metal, plastic, roofing materials, fiberglass glass, vinyl, pick-proof cement, painted surfaces, cement, wood, and other surfaces.

    The product tolerates a wide range of temperatures, bonds to 2,000 psi, is flexible to 500% elongation, and is rated for a 30 year life. We are using this adhesive to bond clear plastic snow brakes to a low slope standing seam metal roof and will report on the results here.

    Surebond SB-190 is not recommended for use on copper or soft expansion joints, nor on polystyrene or styrene-containing plastics.

    Watch out: some adhesive products such as Surebond's SB-190, while very effective, also contain toxic VOCs and other chemicals including Heptane (CAS # 64742-89-8) and Toluene (CAS # 108-88-3). Be sure to read and follow the manufacturer's installation and use instructions.

    Watch out: buy more adhesive than you think you'll need. We were gluing 30 Berger snow guards in two rows and estimated using three tubes of sealant. I bought six and ran out while gluing the 30th guard.

    This sealant is not so easy to spread, making following the manufacturer's instructions to leave no air bubbles and be sure there is runout around the snow guard a little bit of a challenge. In turn that meant using more sealant than anticipated, and possibly more than necessary, as you'll see below. Better to use too much and be a bit ugly than to use too little and have ice heaves and freeze-thaw cycles push the snow guards off of the roof.
  • Buy necessary cleaning supplies: paper towels, denatured alcohol or other surface cleaner, gloves, etc. if you don't already have these on hand. Don't start a job high on a roof without thinking you've got everything you need.
  • Check the weather against the snow guard manufacturer's instructions. When you're gluing snow guards you want the temperature to be above 50F, the roof surface to be dry, and you want a weather prediction of no rain while you're working.

    Watch out: you also want to wait until after the snow season. Snow load will push newly-glued snow guards down the roof and off.
  • Make other on-roof repairs first: if you need to repair gutters, plumbing vents or something else that is anywhere around the to-be-glued snow guard area, do that work first so you won't go walking among and kicking askew the newly-glued guards.
Clean snow guards before gluing them to the roof surface (C) Daniel Friedman
  • Clean the snow guards before installing them on the roof. Release agents, grease, dust, dirt on the snow guard bottom surface can prevent good adhesion to the roof surface.

    In the photo at left we're using denatured alcohol to clean the snow guard bottoms before taking them up to the roof.

    After cleaning these parts keep your greasy fingers off of the guard bottom, or clean the guard again before installation if necessary.
  • Read the instructions from the manufacturer regarding how the snow guard adhesive should be applied - how much, at what temperatures, with how much runout at the edges of the snow guard.
  • Watch out: Secure your ladder and follow safe on-roof work practices. Working on roofs leads to more serious fall injuries than most other construction jobs. Then bring the work materials to the roof surface.

Installing the first snow guard (C) Daniel Friedman Eric Galow, Galow Homes, Poughkeepsie NY, prepping the roof surface for snow guard installation (C) Daniiel Friedman Eric Galow

  • Clean the metal roof surface in the area where the snow guard is to be glued. The surface needs to be clean of dust, dirt, oil, release agents, waterproofing agents (such as silicone spray), and water. We use isopropyl alcohol which has not, in our experience harmed the metal roof's finish surface.

    At above left you can see alcohol for cleaning the roof surface, adhesive & caulk gun, paper towels, a bag for trash, gloves, my wood spacing stick, measuring tape, blue masking tape, and the first snow guard glued in place and secured with tape.

    At above right Eric is using alcohol to clean the area where the snow guard will be bonded to the roof. We worked as a team, one man cleaning and marking, the other gluing, pressing, and taping each snow guard in place.

    Watch out: Some other solvents such as acetone are not recommended as they will dissolve paint or other coloration on the roof, while other recommended solvents such as xylene may work well but can be highly toxic and thus more dangerous to handle.

    We used simple denatured alcohol to clean the metal roof surface as well as the surface of plastic glue-on snow guards.
  • Clean the roof surface again if you've walked over the area where you're about to glue. Make sure the surface is dry too.
  • Measure & mark the snow guard locations. Eric Galow (Galow Homes, Poughkeepsie NY) and I used a pre-cut scrap of wood to mark the lower snow guard location and to space each one uniformly away from the metal roof standing seam. On this low slope roof, 16" up from the roof edge marked the building exterior wall, over which the first row of snow guards was placed. Measuring up 31" to the bottom of the second staggered row of snow guards gave us the location for the second row.

Berger snow guard glued in place on a low slope standing seam metal roof (C) Daniel Friedman Eric Galow

  • Apply the adhesive sealant to the snow guard bottom and press it in place. Get in a good working position so that you can both apply an even coat of adhesive to the guard bottom (uneven coating means air bubbles means poor adhesion) and also so that you can quickly press the guard into position after it's coated. Press down uniformly and firmly until there is adhesive runout and so that the snow guard is not tipped.

    Watch out: pay attention to the "UP" arrows marked on the snow guard. Placing a snow guard in the upside down position will reduce its ability to withstand the force of snow and ice on the roof. Each Berger snow guard is embossed with two arrows and the word "UP" - the longer tail of the snow guard goes down-roof.

    Adhesive runout: use enough adhesive that there are no air bubbles under the snow guard and that there is a runout of about 1/8 to 1/4" (it can be tooled) around all of the edges of the snow guard in contact with the roof. This detail helps prevent water from getting below the snow guard where freeze-thaw cycles will try to push it off of the roof.

    Watch out: Leaving no adhesive run-out may look better but it asks for snow and ice push that ultimately loosens the snow guard. At below right you can see the runout at the last snow-guard we installed - as we ran out of adhesive sealant. I made sure that there was runout at the up-slope and sides of this snow guard. After the initial sealant had cured sufficiently I re-visited the roof, inspected every snow guard and installed additional sealant at any edge that looked suspicious including the lower or down-roof edge of the guard at below right

Berger snow guards taped in place on a metal roof (C) Daniel Friedman Eric Galow Poughkeepsie NY 2014 Plastic snow guards showing adhesive runout (C) Daniel Friedman Eric Galow

  • Keep the snow guards in position: Use string, blue making tape, or other support clamped across the roof to hold the snow guards in place until the adhesive is fully cured.

    String: really? In my opinion, using string to keep the snow guards in place, recommended by some manufacturers, is ridiculous. Because even a tight string will sag under pressure, you'd have to clamp the string to every roof seam. We liked the blue masking tape because it will peel away later without leaving residue on the roof.

Plastic snow guards on standing seam metal roof - temporary tape removed (C) Daniel Friedman

  • Snow guard adhesive curing time: the adhesive used with glue-on snow retainers often needs up to four weeks to cure, longer if temperatures are below 50 degF

    During the curing process the snow guards may creep down a hot roof, a cold roof, a dirty roof, a roof that was wet during installation, or just because the roof god was not on your side. .

    Above at the previous bullet you can see our snow guard taped in position across the lower end of the metal roof using blue masking tape.

    Indeed, checking the adhesive 24 hours later, while it had formed a not-sticky skin, it was still very soft. On a steep roof or in adverse conditions it's no surprise that the snow guards might creep own the roof.

    Since this adhesive sealant needs 4 weeks to fully cure we just left the tape up there for a while.

    At above left you can see the clear plastic Berg snow guards after the blue tape had been removed. Two weeks after installation the adhesive was not fully cured. We were also into May and not worried about snow accumulation pushing these snow guards off of this low slope roof.

    Watch out: do not glue-down snow retainers on a metal roof or any other roof surface before the end of the snow season. If there is a heavy snowfall before the adhesive/sealant has fully cured the snow guards may be pushed out of position or may be pushed completely off of the roof by the weight of snow and ice.

Watch out: What happens if you defer installing snow guards on a roof where they're needed? Take a look at SNOW GUARD FAILURES and at PLUMBING VENT REPAIR and you can see both damage and how that damage was later repaired.

  • Corrugated metal roofs also accept snow guards, typically made of bronze or galvanized iron and referred to as a Snow Guard Shoe.[1]
  • Slate roofs (photos shown earlier in this article series) using long horizontal snow brakes mount the brake or fence on brackets nailed to the roof, with the nailed portion of the mounting bracket extending up under succeeding courses of slates to avoid risk of leaks around mounting bolts.

 

Continue reading at SNOW GUARD SPACING & PATTERN or select a topic from the More Reading links shown below.

or see SNOW GUARD FAILURES

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