Let’s assume you’ve read my blog about the difference between pad-style snow guards (deterrent) and pipe-style snow guards (barricade). These previous posts are available on the Alpine SnowGuards website to help you determine which snow guard is right for your project.
In the past, I’ve used the famous Frank Lloyd Wright approach to architecture design: Form Follows Function. It starts with an understanding of the problem. Any time you have pedestrians, automobiles, points of egress or property of value (hot tubs, patio furniture, grills, landscaping, etc.) in the path of a sudden release of snow and ice, use pipe-style snow guards. Just be certain to use these systems properly.
A quality snow guard manufacturer will gather information about roof pitch, roof type, ground snow load (this building code information is available nationwide, but varies greatly) and distance from eave to peak. This information is used to calculate the potential weight of the snow and ice that needs to be retained (we designed our Online Project Calculator specifically for this).
Given the weight and the strength of the chosen snow guard system, the manufacturer can then recommend the spacing of the pipe brackets, as well as whether or not one tier along the eaves of the building will adequately support the loads. Yes, you read that correctly: One tier of pipe-style snow guards is not always strong enough to manage a given snow load. If you think about typical snow fall amounts in the Washington D.C. area, where there are a lot of Alpine pipe-style systems installed (see below images of Alpine SnowGuards installed on various buildings around Washington D.C.), versus the mountains of Colorado where multiple tiers may be required (photos also below), it’s easy to understand that this is a mathematical equation based on the particular properties of each project.
If you need to protect gutters, plumbing vents, shrubs and other items that are replaceable, like roof vents or lower roof surfaces, pad-style snow guards are often the easiest and most logical solutions. Look for a pad-style snow guard with a design that will hold or grip snow. Physical strength is important – just not as important as function. For example, if you were to install 1/4” diameter rebar, bent at a 90°angle with 4” standing vertically off the roof surface, each bar might withstand 800 pounds or more without bending. However, a 1/4” semi-round device will likely hold back very little snow volume.
Look for pad-style snow guards that spread the load as evenly as possible over the entire roof surface. Pad and wire loop style snow guards are very appropriate for the Washington D.C. area, while they would likely not support the snow mass of more mountainous regions like the Rockies.
Think about the roofing material being installed. If you’re following my blog series about the evolution of snow guards beginning in the late 1800’s, this topic is discussed at great length. One of the key differences between snow guards that were used from the late 1800’s to the 1960’s is roofing material thickness (I know this is a broad comment since graduated thickness slate roofs, thick tiles, cedar hand-split shingles, etc. were around during that era).
The lion’s share of slate, asbestos, asphalt shingle, metal shingle and clay tile (although tile was thicker – 5/8” thick typical for clay slab shingles) were in the 1/4” thick range, or less. This notion is supported by the invention and subsequent copies and knockoffs of the E.W. Clark snow guard design from 1899. Generally speaking, if the snow guard is 1” taller than the thickness of the shingle it’s being installed on, and if the snow guards are installed in the proper quantities, they’ll add the necessary friction to function as a deterrent. Width is also important. It’s my opinion that a wider base (at least 1.5”) is better than something 1” or less (back to the rebar concept – I would agree that if enough rebar was used, they would work great).
In today’s roofing market, there are a number of roofing products that are thicker than 1/4”, including multiple synthetic shingles that mimic thick slate, cedar hand-split shingles and tile. A typical concrete roof tile is 1” thick or thicker. If the snow guard you choose is not 1” taller than the thickness of the chosen tile, be sure the snow guard is set so that the head is a minimum of 2.5 times below the butt of the next vertical course of shingles (see example below). This will allow the slowly migrating mass to slump up over the butt of an upslope shingle course and still fully engage the face of your pad. Having said this, the preferred height of a pad-style snow guard would still be the thickness of the shingle plus a minimum of 1”.
It’s also important to consider the construction or composition of the roof shingle itself. Cedar shingles have become very expensive, and in some areas, they’re not permitted for use due to fire codes. However, they have a very desired aesthetic appeal, which has opened the door for synthetic manufacturers to produce plastic and super compounds that compete on a number of levels (cost, speed of installation, longevity, etc.)
With natural cedar shingles the snow and ice stick to it and rarely slide off – this is not the case with some of the new synthetics. As you can imagine, snow and ice slide off the plastic surface of the synthetic. This is something of a new phenomenon that nobody had ever really thought about before. Sure, some of these new synthetics seem to be excellent products, and like any new roofing product, new issues are bound to spring up.
The principles of pipe-style versus pad-style snow guards apply, and my experience has taught me that frictionless surfaces like glass (solar panels), membrane (commercial products being used on sloped surfaces), and plastics should really utilize pipe-style systems around the base of the installation. If multiple tiers of pipe-style snow guards are recommended but not desired, consider supplementing the bottom tier of pipe-style snow guards with pad-style snow guards. The Alpine customer service staff can assist with these options and help answer your questions, just send us an email or give us a call at 888-766-4273 – that’s what we’re here for!
President & Founder, Alpine SnowGuards
We keep snow in its place
Sign up to start using our Online Project Calculator for an immediate layout and project pricing!
Subscribe to our monthly newsletter and keep up on the latest industry and Alpine news, products and upcoming events!
Alpine SnowGuards designs, engineers, and manufactures snow management systems from our facilities in Morrisville, VT. We work closely with leading roofing contractors, engineering firms, developers, and roofing manufacturers to ensure we deliver quality products that do what we say they’ll do. Alpine SnowGuards can help a building qualify for LEED® credits.
(Images from: James Myers Co., Formula Roofing, Create Luck LV and Alpine SnowGuards’ Archives)