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tDA-$B uR, P[HdB"(TYG3~2aC8SRyc7M 6*/])tuE f#-k_((H `C'Jr2vy%2u6cr 9|^}!s+RlQdL u_ -7+$X{lOY{"lW|L+TE r]Ep}1{'9/h]~Bl_ or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX. The panel type and material, roof size, local snow loads and aesthetics are some other issues to consider.. 5 0 obj Privacy Policy | Terms of use | Legal & IP. endobj endobj Metal roofs are a smart decision. Panel: Valley width between 16 inches and 24 inches. Watch out: Berger Building Products (ret 2014) warns that, Snow guards should never be placed beyond the bearing wall on an extended roof section. Note: appearance of your Comment below may be delayed: if your comment contains an image, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Roof Tiling & Slating, a Practical Guide, Kevin Taylor, Crowood Press (2008), ISBN 978-1847970237. This first method uses a seam-clamping attachment. When deciding on the right type of snow retention system, Haddock says to be sure the design is adequate and specific to your application, with appropriate testing. Apologies for the delay. Feasterville, PA 19053 ISBN-13: 978-0471331728, Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) Starting at 6 inches from the bottom edge, place 2 snow guards equally spaced apart in the valley, in a staggered pattern, across the entire roof area. Tel: (860) 229-SNOW (7669) provides clear or colored plastic snow guards for metal and rubber roofs, available in "King" and "Queen" sizes. Go up the roof 5 feet and repeat the staggered pattern of guards in the center of every valley. For Example: if your roof sheets are 16 feet long, your roof would require a row at 1 foot from the bottom and at 8 feet up from the bottom.

Lesser quality paint finishes on the snow guards will fade more rapidly than the roof, producing a very unsightly mismatch within a few years, Haddock notes. Snow load: Up to 45 PSF ground snow load. Pitch: 7/12 up to 12/12 pitch. !pN,SeX.5m5ldUk[]pZQp=8O@{xxR}3DiBocHu%.NugkMi;$ P'd_h) \v[SwtcB K3{ XE2OJ=d@>r=h{cN)lfym A\},jaz]Vh+zibN6wUn/5* 5Z$FVIM`9Hz%%%t,RfZM @ *d. These have at least two components: brackets or seam clamps that are attached to the roof, and cross-members that are anchored to the brackets or clamps that restrain the sliding snow. All snow guard devices rely upon the compressive strength of a bank of snow to resist its downward migration. >>

81-50643. For Example: if your roof sheets are 26 feet long, your roof would require a row at 1 foot from the bottom and at 13 feet up from the bottom. , ISBN-13: 978-0764330018, Low Slope Roofing, Manual of, 4th Ed., C.W. With S-5! Terms of use, which are legally binding upon you, govern your use of this site and any products manufactured by Metal Roof Innovations, Ltd., and provide rules that prohibit unlawful use or copying of any part of this site. Griffin, Mcgraw-Hill (Tx); 2nd edition (July 1982), ISBN-10: 0070247838, ISBN-13: 978-0070247833, Concrete Folded Plate Roofs, C. Wilby PhD BSc CEng FICE FIStructE (Author), Butterworth-Heinemann, 1998, ISBN-10: 0340662662, ISBN-13: 978-0340662663, Copper Roofing, Master specifications for copper roofing and sheet metal work in building construction: Institutional, commercial, industrial, I.E. endobj endstream They are also protected from harmful UV sunlightand they utilize part designs that prevent over-compression which can also compromise their service life. endobj Snow load: Up to 45 PSF ground snow load. The buildup of snow and ice on a pitched metal roof causes challenges in many areas around the country. It is important that the snow guard system is designed for each specific project. ] evenly distributed snow load will preserve the long-term integrity of the actual When possible, always attempt to divide the roof areas into equal sections, with equal distance between rows, without exceeding the manufacturer maximum placement guidelines. For Example: if your roof sheets are 8 feet long, your roof would require a row at 6 inches from the bottom and at 4 feet up from the bottom. <>/ExtGState<>/Font<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 611.76 791.76] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> % *CD|~W_w?Cb7$R*k>h#4;o_}!f> |O A_$(O10c'6|@/1c||) jXZM?7M3_9A QV>P9MjY4 HoQ#4Sep*3I/S|15cZrGN;hO@HKxQU4ycUnC~!ge}L'WUSg2}hUvSwn7]]zadCk%V_:UOnE,usgS+'9x9yt>We]]D9mxJ)KLM58(-p*1'`4!nk]seW.{>,;3Y3kjrvI% +'p>o1ij. Learn more about installing snow retention systemswith mechanical attachment via clamp mounting or structural attachment and weather proofing at S-5.com. [4] 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. Metal Roof Innovations, LTD. Do not exceed 8 feet vertically between rows of guards. Since they represent a load chain to transfer the sliding forces of snow into the building structure, each link in the chain must be proven to be able to withstand the forces to which it will be exposed. 2014). A unitized snow guard can be a single- or multi-component and does not use continuous cross-member. Choosing the right type of snow guard is a decision largely based on aesthetic and personal preference. Use aluminum with stainless hardware on coated steel and zinc roofing; brass alloys or stainless for copper roofing; anodized aluminum or stainless for stainless roofing, adds Haddock.

According to Haddock, the method of attachment of snow guards should be consistent with the roof type. And holes in a metal roof need to be properly weather-proofed to prevent leakage. McGraw-Hill Professional; 4 edition, 2006, ISBN-10: 007145828X, ISBN-13: 978-0071458283. For installing snow guards, most of the tools needed are common to the trade. Snow guards should always be placed at the lower half of the roof plane. The International Energy Conservation Code (IECC) and the American Society 1994-2022 Modern Trade Communications Inc. No data on this website may be downloaded or copied for use on other websites or in other publications without prior written consent from this sites webmaster. hbspt.cta._relativeUrls=true;hbspt.cta.load(3482954, '39ba9b6e-ad54-461a-ba95-d72626296534', {"useNewLoader":"true","region":"na1"}); The third type of snow retention is a stick-on (adhered) part. Panel: Valley width less than 16 inches. We're confident that our retro-fit snow guard installation method will provide secure, leak-proof attachment for the life of the roof. Use: 2 snow guards per valley every 15 feet of roof. Go up the roof 10 feet and repeat the staggered pattern of guards in every valley as placed below. Go up the roof 10 feet and repeat the staggered pattern of guards in the center of every valley. [0dFnY!OOna}Ca[(F4r-RJ 0`h[02r:Ojuxw|7%7&?Y3v2YFVv^:7Q&lon:wKQ&k@l_`?a[(h$e7n (H\g`Oa(Q& :uQJLQS3HF%2YIvfdQ&k i:RZFE) 3 QILQRuT(JHkcPR1`&B. The third is chemically-attachedand uses a stick-on method, which involves gluing individual snow guards to a roof. Individual snow guard mounting methods vary depending on the roof covering material. Go up the roof 8 feet and repeat the staggered pattern of guards in the center of every valley. Continue reading at SNOW GUARD BUILDING CODES? Go up the roof 15 feet and repeat the staggered pattern of guards in every valley as placed below. A quality snow retention system will help you maintain your roof, avoid personal and property damage, and efficiently and safely allow snow to melt off your structure. 2022 S-5!. Similarly, fasteners should also last the life of the roof. By using this site, you agree to abide by the Terms of Use. Panel: Valley width less than 16 inches. Drilling requires holes. Use: 1 snow guard per valley every 15 feet of roof. the roof is not always enough protection against this dangerous condition. area to keep snow and ice from shifting initially. Use: 2 snow guards per valley for every 8 feet of roof. Call Toll Free: (877) 414-7606 Morrisville, VT 05661 Tel: 888-766-9994, Email: info@alpinesnowguards.com Website: http://www.alpinesnowguards.com/ [No direct retail sales], [6] ATAS Snow Retention Products, ATAS Headquarters

When this method is used, the sliding force of the snow is transferred to the clamp and then into the roof panels themselves. Snow load: Up to 45 PSF ground snow load. endobj

A properly tested, engineered and designed snow guard system is imperative to resist the forces induced by snow packs.

[8] 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. products, you will need to perform additional steps to waterproof these roof penetrations, and you will have to know something about sealant chemistry, part design, sealant selection/sourcing, etc.). Snow load: Up to 45 PSF ground snow load. When they fail, they can rip away paint and protective roof coatings, causing corrosion. %PDF-1.5 stream We have never heard of an issue with our snow guards causing a leak. Failure of a snow retention system can cause property damage and potential loss of life. Technical Resources from the Metal Construction Association: For more information, visit www.metalconstruction.org/Tech-Resources. When possible, always attempt to divide the roof areas into equal sections, with equal distance between rows, without exceeding the manufacturer maximum placement guidelines. Some variations employ a factory-applied adhesive (chemical-attachment) and others a field-applied one.

As Haddock notes, the steeper the roof, the greater the forces are that act on the snow guard assembly. Do not exceed 5 feet vertically between rows of guards. 289 Harrel Street For Example: if your roof sheets are 8 feet long, your roof would require a row at 6 inches from the bottom and at 4 feet up from the bottom. But with metal roofs, you must consider the risk of roof top avalanches. Iron Mountain, MI 49801, Tel: 06-396-7000, Email: mark@snowgripit.com Website: http://www.snowgripit.com/. Axqb"$3Z-XV+[B%6ac\MpP$BPNogPkXqTa6gIevSqT.v} cH (dEYFQdE {.2&{.: Spacing requirements for snow retention devices vary depending on the roof slope or pitch. What is the Best Way to Mount Snow Retention to a Metal Roof? XK Copyright 2022, Rocky Mountain Snow Guards, Inc. All Rights Reserved. dEGARp`MRfEA!w=90$s` f rxCR )A!r 90G5 These parts attach directly to the roof with a glued application. Stick-on systems appear on the surface to be a very convenient and lower cost option. structure, metal roof and snow retention system. Email: info@atas.com, Website: http://www.atas.com/Company/Contact.aspx. With the use of a proper sealant under the snow guard strap, the snow guard will be as water tight as the roof covering itself. MCA (Metal Construction Association) technical documents are the greatest aid available for snow guard selection criteria and downloads are free. Therefore, a face-fastened roof should use a face-fastened snow guard attachment with butyl copolymer sealants and fasteners of no less quality than those used for the roof itself. At S-5!, we manufacture and market clamps and brackets to reliably mount snow guard systemsto metal roof seams with clamps and setscrews that compress the seam material against the opposite wall of the clamp dimpling the material, but not penetrating it - and without creating holes. [ /DeviceN [ /Cyan /Magenta /Yellow /Black The holding strength of such a system should be documented through rigorous testing and must be able to resist the loads to which it is exposed. Continuous snow guards can be made up of one or multiple cross-members. Metal Roofing, an Illustrated Guide, R.A. Knowlton , [metal shingle roofs], Problems in Roofing Design, B. Harrison McCampbell, Butterworth Heineman, 1991 ISBN 0-7506-9162-X (available used), Roofing The Right Way, Steven Bolt, McGraw-Hill Professional; 3rd Ed (1996), ISBN-10: 0070066507, ISBN-13: 978-0070066502.

endobj 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. Englewood, CO 80110. Our approach to proper /Range [ 0 1 0 1 0 1 0 1 They also have the lowest lifespan due to the glue and/or plastic part being unable to handle the harsh elements and total exposure that is required on any roof (e.g. /Domain [ 0 1 % Normally used in a redundant fashion, unitized snow guards rely on the bridging of a snowpack to span between adjacent devices to limit snow migration.

In its newest technical bulletin, Qualifying Snow Retention Systems for Metal Roofing, MCA recommends snow guard systems for metal roofs to be manufactured from non-corrosive metals. 4231 S. Natches Court, Unit C Handbook of Building Crafts in Conservation, Jack Bower, Ed., 1 0 obj Exposed fastener heads should be AlZn alloy or 300 series stainless steel, and washers should be black EPDM, adds Haddock. Young, Wiley (March 21, 2008) This can result in ice damming and cause structural damage. Always consult with an architect or engineer for recommended snow guard placement for your project. /Length 76 0 R Either type can workcontinuous rail or discontinuous cleat-type systemsprovided that either is appropriately tested, correctly installed and proven by engineered calculation to resist the in-service loads presented on a site-specific basis, says Rob Haddock, CEO of Colorado Springs, Colo.-based S-5! Snow load: Up to 45 PSF ground snow load.

Our Comment Box is provided by Countable Web Productions countable.ca, Click to Show or Hide Citations & References, HOME INSPECTION EDUCATION COURSES (Canada), HOME INSPECTION EDUCATION: HOME STUDY COURSES, "Snow Guard Technical Appendix", A7 1/12, Amerimax Home Products, Inc., Tel: 1-800-827-4369, Website: http://www.amerimax.com, retrieved 5/2/14, Email: info@amerimax.com, original source http://www.amerimax.com/pdf/catalog/snow%20guard%20tech.pdf, [1] Berger Snow Retention Systems, Berger Building Products, 805 Pennsylvania Blvd. Pitch:1/2/12 to 2/12 pitch. Use: 2 snow guards per valley every 10 feet of roof. Copyright var date = new Date(); document.write(date.getFullYear()) IceBlox Inc. d.b.a. 2 0 obj Dont just believe what we say because we said it! But there are a number of methods to mount snow guard systems. And, depending on the system, snow guards can be placed in a single line, or in multiple rows. <>/PageLabels 547 0 R>> Attachment Solutions, Metal roofing is indeed a slippery slope (pun intended), as you must consider the risk of roof top avalanches (personal danger and property damage), as well as the need for snow removal maintenance. ] And all of our USA-made clamps and brackets are backed by an industry-leading limited lifetime manufacturer warranty. ISBN-10: 1405161035 installed snow guard system canmitigate this condition. If the slope of the same roof is changed to 7:12, the force changes to 1,008 pounds per linear foot.. MCAs technical bulletin, Metal Roof Design for Cold Climates, can be used as a reference guide for snow retention calculations and placement.

Colorado Springs, CO 80908 For through-fastened roofs, Haddock says sealants should be at least equal in performance to those used in the roof itself. components, we take the guesswork out and provide an appropriate system with sealants factory-applied. /FunctionType 4 Snow retention systems reduce the risk of sudden rooftop avalanches and mitigate the hazards present in the area below the eaves. Because metal roofs have exhibited service lives of more than 60 years in documented field studies by the Metal Construction Association (MCA), this requirement immediately rules out the use of plastics (polycarbonates) as they do not measure up to such a service life in outdoor exposure, he adds. uR( -IdlH"(dEYG! Pitch: 7/12 up to 12/12 pitch . 3 0 obj For Example: if your roof sheets are 26 feet long, your roof would require a row at 1 foot from the bottom and at 13 feet up from the bottom. products, you will need to perform additional steps to waterproof these roof penetrations, and you will have to know something about sealant chemistry, part design, sealant selection/sourcing, etc.). A quality snow retention system will help preserve your roof and allow snow drifts and snow melt to exit the roof in a more controlled manner. Because they know our rigorously researched, tested and quality engineered products deliver unprecedented value and innovative excellence. The Woodbinder Eclipse has a large head that covers and "encapsulates" the rubber grommet beneath. << Email: info@rockymountainsnowguards.com, Rocky Mountain Snow Guards (Suddenly, this is not as simple as it first seemed to be). Panel: Valley width between 16 inches and 24 inches. Attachment Solutions. Pitch:1/2/12 to 2/12 pitch.

] Do not exceed 10 feet vertically between rows of guards. Van Nostrand Reinhold Company, NY 1981 ISBN 0-442-2135-3 Library of There are three basic methods available for mounting snow retention systems to roofs. Isolating snow guards on partial roof sections such as just over doorways or roof vents is not recommended. 2 0 obj ISBN-13: 978-1405161039, Built-Up Roof Systems, Manual, C.W. You can view these results directly on our website at S-5.com under the Load Test Resultstab located at the bottom of the page.

6 0 obj - Berger Snow Guard Guidelines, op.cit., retrieved 5/2/2014. With snow guards that attach directly to the structure, holes will need to be drilled (or other penetrationsrequired) to anchor snow guard brackets, to ensure secure placement and the long-term service life of the roof.

Snow Fences Protect Congregation at Ski Area Chapel. XyH{?TfBW5" 7y&?9RT7oW[?fGGKe4o~zz.~zoc$u8mM6|x-uQ =Ew;Cg!;@u! A; `8Da?l xEKs\_|a1n~$z^Etz`\uL# ?Gjw]*`k%6S1yt/m*Iz3^M? SNOW GUARD SPACING & PATTERN at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice. Generally speaking, if installing one row and using a continuous rail-type system, your snow retention would be installed approximately 1 to 2 feet from the eave, explains Tom Grant, branch manager at Dynamic Fastener. Tel: (860) 229-SNOW (7669).

At S-5!, we take the magic out of all that with web-based tools, enabling you to do all this quickly and easily. /FunctionType 4 AND we test and warrant their performance in accordance to ASTM E 2140. [7] Pacific Sheet Metal, For this reason, the snow banks downslope extremity is the best place to interface with snow guards., Additionally, Webber notes, Slope is a critical component in the engineering/design of snow retention because steep slopes combined with long panel lengths are two of the factors that help determine if multiple rows of snow retention are needed.. %PDF-1.3 [0@naBB

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. If this is not done correctly, you run the risk of developing leaks. Select your pitch below to get a general spacing guideline. The Woodbinder Eclipse is specifically designed as a fastener for exposed fastener metal panel roofs. Pitch: 3/12 up to 4/12 pitch. But if you look more closely at the detailed instructions, installation becomes a bit more complicated careful surface preparation is required, as well as many days of curing time at specific temperatures. 8655 Table Butte Road {.p:sDQH$B << Anderson, 1961 (hard to find), Corrugated Iron, Building on the Frontier, Simon Holloway. [5] Alpine SnowGuards For panels wider than 16", please scroll down to see the next drawing below. Relying on caulk/adhesive for attachment is not the preferred method, whereas using a mechanically fastened clamp/rail combo is the stronger alternative, says Grant. seam style metal roof. Continuous snow guards are otherwise known as rail type snow guards, snow fence, snow rail or pipe-style snow guard. 4 0 obj Snow load: Up to 45 PSF ground snow load.

Allentown, Pennsylvania 18106 3 0 obj

He recommends asking the manufacturer for written proof of appropriate testing on the chosen roof profile or substrate by an accredited lab. But there are steps to take to thwart dangerous roof top avalanches. Jerod Webber, sales manager, at Raytown, Mo.-based Dynamic Fastener, notes that engineering and testing is one of the main focuses when choosing a snow retention system. FAX: 610-395-9342 What is the best way? Snow guard layout & spacing on all roofs. For Example: if your roof sheets are 12 feet long, your roof would need a row at 6 inches from the bottom and at 6 feet up from the bottom. Panel: Valley width between 16 inches and 24 inches. The Slate Roof Bible, Joseph Jenkins, www.jenkinsslate.com, In parts of the /Filter /FlateDecode

Email: info@bergerbuildingproducts.com, Website: BergerBuildingProducts.com, [2] Precision Snow-Guards, AceClamp, Standing Seam Metal Roof Supplies, Precision Snow-guards - c/o PMC Industries, Inc. Preferred sealants are isobutylene/isoprene (butyl) polymers or materials with similar of greater service life, while ethylene propylene diene monomer (EPDM) or similar materials are the preferred washer chemistry, using carbon black UV stabilizers. Starting at 1 foot from the bottom edge, place a snow guard in the center of each valley, in a staggered pattern, across the entire roof area. /Subtype /XML Check out ourretro-fit snow guard installationinstructions and video. Alpine Snow Guards recommends placing a three row pattern on the lower roof, 24" o.c.

Clamps attach directly to the roof seam using polished, round-point setscrews that do not penetrate the metal (mechanically-attached). All Rights Reserved.

Clamps attach directly to the roof seam using polished, round-point setscrews that do not penetrate the metal (. If you own property with a metal roof in snow country,you definitely understand the importance of snow retention. The company provides a line of very sturdy snow rails or fences that mount to the seams of a metal roof. To accomplish this, prior to installation with other (non-S-5!) The Woodbinder Eclipse is a commercial grade roofing screw that is manufactured specifically for this type of work. using the process of either clamping to the seam (non-penetrating) or screwing through the roof material (penetrating). Phone: 800-468-1441 Do not exceed 15 feet vertically between rows of guards.

All snow retention systems use one of these methods to provide snow and ice retention for building roofs.

It is critical to understand the unpredictable nature of snow melton a metal roof. The compatibility between different types of metals is an important consideration when choosing a snow guard system. endobj

1 0 obj We have no relationship with advertisers, products, or services discussed at this website. /Type /Metadata Starting at 6 inches from the bottom edge, place a snow guard in the center of each valley, in a staggered pattern, across the entire roof area. A properly

/Range [ 0 1 0 1 0 1 0 1 << We're confident that our retro-fit snow guard installation method will provide secure, leak-proof attachment for the life of the roof. When installed, stick-on snow guards typically have the lowest holding strength (which continues to diminish with age).

Whether residential or commercial, you have already madea smart decision by choosing a roof that has the longest service life possible. Panel: Valley width less than 16 inches. (888) 825-3432, Email: info@s-5.com, Website: http://www.s-5.com/snow/. For example, a 4:12 roof that is 50 feet from eave to ridge with a 40-psf design roof snow load will exert 633 pounds per linear foot of eave on the snow guard assembly, he explains. Qualifying Snow Retention Systems for Metal Roofing, Fastener Compatibility with Profiled Metal Roof and Wall Panels. A combination of testing, science, mathematics and quality control are required for the proper design of snow guard systems. Use: 2 snow guards per valley for every 5 feet of roof.

stream 76 Tags: components, we take the guesswork out and provide an appropriate system with sealants factory-applied.

This page should only be used only as a quick reference guide for estimating snow guard quantities and placement on roofs with less than 45 PSF ground snow load. For Example: if your roof sheets are 16 feet long, your roof would require a row at 1 foot from the bottom and at 8 feet up from the bottom. In general, snow accumulates on a roof with greater concentration near the eaves and valleys due to wind scouring. <> We can provide them with all the information necessary to ensure that they install these snow guards correctly and in a fashion that is compatible with your specific roofing system. placement involves an overall spacing throughout the entire roof Go up the roof 8 feet and repeat the staggered pattern of guards in every valley as placed below. For panels wider than 16", please scroll down to see the next drawing below. If this is not done correctly, you run the risk of developing leaks. metal roof brackets, Xa3Y0dFja}Ca For more information, please do not hesitate to contact us! Snow load: Up to 45 PSF ground snow load. Visit MCAfor more information. 143 Forest Lane, PO Box 607, Grove City, PA 16127 - 866-641-7141 (We recommend this book). Starting at 6 inches from the bottom edge, place a snow guard in the center of each valley, in a staggered pattern, across the entire roof area. There are unitized snow guards, otherwise known as discontinuous snow guards, snow cleats or pad style snow guards.

endobj

Go up the roof 5 feet and repeat the staggered pattern of guards in every valley as placed below. /Length 77 0 R ] /DeviceCMYK 2 0 R [emailprotected] (717) 697-1900. Do not exceed 15 feet vertically between rows of guards. All Rights Reserved. 'S]A0>hn[vtQ;LHOB>u $=3$Zp?"760J~TQ(~A Xv:D8bEl T@12Q_9B :D Fc3 MrL{f8v PU a2 @w&-pr$P}u>P#w^XV(j$PH2BnxaDBx:a4 [9] AMSI Supply 4333 Lynwood Ct, Douglasville, GA 30134, metal roofing components, Tel: 800-943-9771, [10] SnowGrip, 126 Woodward Ave., No street address was provided. When choosing washers or sealants for waterproofing, use ones with the same chemistry as the washers and sealants present in the roof system to ensure a similar expected service life. /Length 75 0 R To properly retain the expected snow load, following the installation instructions is crucial.. Starting at 1 foot from the bottom edge, place 2 snow guards equally spaced apart in the valley, in a staggered pattern, across the entire roof area. /Filter /FlateDecode ISBN-13: 978-0471788362, Historic Slate Roofs : With How-to Info and Specifications, Tina Skinner (Ed), Schiffer Publishing, 2008, ISBN-10: 0764330012