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Snow guard layout & spacing on all roofs. This article describes how to lay out the snow retainer or guard pattern on a roof in order to provide an effective snow retention system. Spacing requirements for snow retention devices vary depending on the roof slope or pitch. We give recommended side spacing between individual snow guard devices & we discuss an important consideration to avoid structural damage: how far up the roof from the eaves should the first row of snow guards begin.
This article series illustrates types of snow guards or snow brakes or other snow retention devices used on metal, rubber, asphalt, and slate roofs.
Snow Retention Device Installation Specifications for Location & Spacing
Snow Guard Spacing Distances side-to-side in staggered rows
Experts point out that for the placement of individual snow guards (as opposed to long horizontal snow fences or snow brakes) depends on the pitch of the roof. According to Precision Snow-Guards
[Click to enlarge any image]
For roofs sloped 0 (flat) to 2 inches in 12 of rise (2/12 Slope), snow guards are placed in one staggered set across the lower roof edge staggered two feet on center. [Why you would need snow retention guards on a flat or 0-slope roof escapes us - Ed.]
Note: Amerimax recommends omission of snow guards on roofs under 3:12. Do not use Snow Guards on low-slope roofs (those with pitches less than 3:12). Snow guards help reduce the momentum of a potential
snow slide. On low-slope roofs, snow does not typically slide off in the same manner. Under these circumstances, it is often better to
allow the snow to naturally clear itself from the roof as quickly as possible or to manually remove it. Therefore, snow guards are not
recommended for low-slope roof applications. Check with the roof manufacturer for specific product application limits and, as always,
observe all roof safety guidelines. - Amerimax (retrieved 2014).
Really? for inaccessible low slope roofs, we share the concern for weight (the structure should have been designed for snow loading but may be under-designed, risking collapse) that arguers to "let the snow fall off of the roof". But I have seen damage from snow falling off of low slope roofs, including damage to objects below and damage to on-roof components such as plumbing vents and gutters.
For roofs sloped more than 2/12 and up to 6/12, install two rows or sets of staggered guards, two feet on center
For roofs sloped at 6/12 and steeper, install two rows or sets of snow guards in straight lines (not staggered) across the roof eaves
For metal loop wire type snow hooks or snow guards (photo at left) you can see that to work at all, since these devices have much less surface area than a flat or bar type snow guard, they have to be installed in many staggered rows over half or more of the roof surface.
The snow hooks shown here are installed on a slate roof at the Justin Morrill Smith historic home in Vermont. Metal loop snow guards for shingle,slate, and cedar shake roofs are typically made of copper wire. See Berger Building Products for a source.
Snow brakes, snow fences, snow rails, or similarly-called continuous bars or fences to retain snow on a building roof are usually installed as a single continuous system across the roof eaves, typically 1 to 3 feet above the eaves.
Snow Guard Row Location: where to place the rows, how to prevent structural damage from accumulated weight of ice & snow
In addition to installing one or more staggered sets of snow guards "across the lower roof edge" with quantity and spacing varying by roof slope (discussed above), we'd like to know how far back from the lower roof edge or eaves should the first row of snow guards begin and how many feet of space should be provided between banks of snow guards on larger roofs with multiple installations of snow guard products.
Place the first row of snow guards at or above the exterior load-bearing wall.
Watch out: Berger Building Products (ret 2014) warns that
Snow guards should never be placed beyond the bearing wall on an extended roof section. This can result in ice damming and cause structural damage. - Berger Snow Guard Guidelines, op.cit., retrieved 5/2/2014
Place the second staggered row of snow guards 15 inches over the center of the first row.
If a third row is used the stagger pattern matches the first row and this row too is placed 15 inches above the center of the second row.
Note: Alpine Snow Guards (ret. 2014) comments that the top ten feet of rafter length of a roof dfoes not need snow guards except in extreme snow load areas.
If a second or subsequent group of snow guards is to be installed higher on the roof, space the second group 6ft. to 8 ft. up-roof from the lower set.
Alpine Snow Guards recommends placing a three row pattern on the lower roof, 24" o.c. with the middle row staggerd 12", and covering the remaining roof to within 10 feet of the ridge with evenlyspaced snow guards between the bottom three row pattern and the top un-guarded area. - Alpine (ret. 2014)
5 Snow Retention System or Snow Guard Installation Mounting Methods
Individual snow guard mounting methods vary depending on the roof covering material. All snow retention systems use one of these methods to provide snow and ice retention for building roofs.
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 Precision Snow-Guards, AceClamp®, Standing Seam Metal Roof Supplies, Precision Snow-guards™ - c/o PMC Industries, Inc.
87 Spring Lane, Plainville, CT 06062
Tel: (860) 229-SNOW (7669) provides clear or colored plastic snow guards for metal and rubber roofs, available in "King" and "Queen" sizes. Tel: (860) 229-SNOW (7669). Website: http://www.snow-guards.com/snowguards.php
 S-5!® Snow Retention Systems, S-5! Attachment Solutions,
Metal Roof Innovations, LTD.
8655 Table Butte Road
Colorado Springs, CO 80908
(888) 825-3432, Email: email@example.com, Website: http://www.s-5.com/snow/
The company's products include milled solid block aluminum snow rail mounting clamps of varying shapes & designs. We are evaluating the S-5! clamps provided by this company. These clamps attach to the standing seams on a metal roof and in turn are used to attach a snow rail or snow fence. The company also provides solar panel hold-downs for metal roofs.- Ed.
 SnoBar™, Tel: 800-711-9724, Website: http://www.snobar.com/index.html The company's products include a patented one-piece roof clamp bracket & other brackets for attaching bars used as snow rails or snow fences. No street address was provided.
 Alpine SnowGuards®
289 Harrel Street
Morrisville, VT 05661 Tel: 888-766-9994, Email: firstname.lastname@example.org Website: http://www.alpinesnowguards.com/ [No direct retail sales]
 ATAS Snow Retention Products, ATAS Headquarters
Allentown, Pennsylvania 18106
Email: email@example.com, Website: http://www.atas.com/Company/Contact.aspx
 Pacific Sheet Metal,
Aspen Office & Shop,
401 Aspen Airport Business Center Aspen, Colorado 81611, Email: firstname.lastname@example.org, Tel: 970.925.2454. The company provides a line of very sturdy snow rails or fences that mount to the seams of a metal roof.
 Gough Snow Guards, Brookfield IL, Tel: 708-485-6272, Website: http://www.snoguard.com/ The company's products include copper snow guards installed on slate roofs and tile roofs, as well as standing seam metal roof snow retention systems.
 AMSI Supply 4333 Lynwood Ct, Douglasville, GA 30134, metal roofing components, Tel: 800-943-9771
 SnowGrip, 126 Woodward Ave.,
Iron Mountain, MI 49801, Tel: 06-396-7000, Email: email@example.com Website: http://www.snowgripit.com/
 Eric Galow, Galow Homes, Lagrangeville, NY. Mr. Galow can be reached by email: firstname.lastname@example.org or by telephone: 914-474-6613. Mr. Galow specializes in residential construction including both new homes and repairs, renovations, and additions.
 "From Asbestos to Zinc, Gutters", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
 Terry Anderson, "Snow Retention - the Invisible Code", web search 7/13/12, original source: http://snow.tra-mage.com/news-articles/snow-retention-the-invisible-code.html [copy on file as: Anderson Dec 2011 Interface.pdf ]
Roofing The Right Way, Steven Bolt, McGraw-Hill Professional; 3rd Ed (1996), ISBN-10: 0070066507, ISBN-13: 978-0070066502
Slate Roofs, National Slate Association, 1926, reprinted 1977
by Vermont Structural Slate Co., Inc., Fair Haven, VT 05743, 802-265-4933/34. (We recommend this book if you can find it. It
has gone in and out of print on occasion.)
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