When should I shovel my roof?
Estimating roof snow loads
There is so much snow! But when is it too much for your roof to bear? Let Zachary Engineering show you how to estimate when it’s time to shovel your roof.
With the massive amounts of snow the Lake Tahoe region has experienced over the last few weeks, the blizzard which loaded some roofs in nonstandard ways and the next storm being a potential pineapple express rain event, Zachary Engineering is recommending that home owners get their roofs shoveled. One way to estimate when your roof is reaching design capacity is as follows:
Step 1 – Determine the ground snow load. Site specific snow loads are available at each County’s website, including but not limited to: Nevada County, Placer County, Town of Truckee, Washoe County, and supersede the snow load calculator on our website.
Step 2 –Using the Ground Snow Load for your parcel/area, we are going to make an assumption for the Snow Density at 25 pcf (pounds per cubic foot). Next, take the ground snow load and divide it by 25 pcf. This will give you an estimate of the Max Anticipated Ground Snow Depth.
Step 3 - Estimate the Max Depth for the roof. You can do this by multiplying the Max Anticipated Ground Snow Depth by 0.7 which will give you an estimate of the max allowable average roof snow depth (does not account for drift, overhang or valley loading). At this early stage in the season, it is better to be conservative. Therefore, we recommend that when the snow depth on the roof reaches 50% of the Maximum Anticipated Snow Depth at ground level, it should be shoveled. For example, if the Maximum Anticipated Snow Depth at ground level is 9.0 ft, then 4.5 ft of snow on the roof would warrant clearing to prepare for the next storm. In addition, common sense should be used. If your roof is approaching that Max Depth number, and there is a large storm on the horizon, then keep in mind that it will likely not be possible to clear during the storm. Therefore, it might be prudent to have the roof cleared prior to the storm’s arrival.
Step 4 - Be safe! While it is possible to clear your roof on your own, this can be dangerous. As such, we recommend seeking the services of an experienced professional. Please keep in mind that each side of the roof should be cleared at the same time whenever possible, meaning that one side of the roof should not be completely cleared until the opposite side of the ridge is also cleared. We recommend clearing in stages. This will help avoid unbalanced snow loads on the roof. There are lots of stories out there about roofs that fail during or immediately after clearing, and the primary reason for this is inadvertently creating unbalanced snow loads for which a roof might not have been designed.
We hope this helps you in your determination! Please feel free to send us pictures of the large amounts of snow on your roofs; they might end up on one of our slideshows!
Note: This approach should be taken as an estimation only, and does not replace the advice of your design engineer. Zachary Engineering cannot guarantee how your individual roof was designed or built, and as such cannot state without a doubt if your roof will fail under certain conditions. The ground snow load does not take into consideration drift, impact, blizzard accumulations or ice dam loading. Seek the advice of your design engineer if your roof is experiencing excessive deformation or if you are noticing any kind of interior damage due to large amounts of snow.
What Is Value Engineering
Why should I care?
We hear the term “Value Engineered” a lot, but are you really getting the full “Value” out of your engineer or architect? If you truly want your project to be value engineered, it’s a good idea to hire an experienced engineer and get him or her on board before the design in complete. It is fairly easy for an experienced engineer to be able to look at some preliminary floor, elevation and section plans and identify areas that may be costing you money that need not be spent. In this climate we receive extreme snow loads, high winds and have the potential for substantial earthquakes (which we have to design in conjunction with a portion of the snow load) requiring a great deal of engineering to make work. An experienced engineer will have done literally hundreds of projects in this climate, and becomes quite good at spotting areas in the design that will cost a lot of money to make work.
TIMBER COSTS
Your engineer must first be familiar with, or know where to get the answers of, the current rough costs of the different lumber that can be used on a project. Take roof rafters for example. We have a variety of choices, each of which has its positive and negative properties. Some of the choices are Rough Sawn Lumber, Trusses, Timberstrand, Parallams, Microllams, Wood I-Joists, Boise Cascade products, TJI products, Steel, SIP’s (Structurally Insulated Panels), etc. We as engineers also need to know the rough installation costs, for some of these products need to be modified in order to work or require some hardware to make work, or may just have a very labor intensive construction cost. It is important to consider these choices as the project is being designed, that is if you want to stay in budget.
DESIGN FLEXIBILITY
Take for example an open living room / kitchen with a tight budget, a vaulted ceiling and a 12:12 roof pitch. Most people like to have the 12:12 interior vault which requires a ridge beam and rafters that can span between the ridge beam and supporting walls. The ridge beam will typically be a Glue Laminated Beam or a Steel I-Beam, depending on the size of the room costing anywhere from 3-$10k. If the room is wide enough, the rafters will likely be Microllams or equal costing 8-$18 / Lineal Ft. You could see the price for that vaulted living room can spiral out of control. Now if you want to save some money and are okay with a 6:12 interior vault, you could use scissor trusses and cut costs nearly in half.
Other areas that we typically look at are the shear walls. An experienced engineer can quickly look at the floor plans and elevations and determine which of the shear walls will work with conventional lumber (2x6 studs and 15/32” APA rated sheathing i.e. plywood). If there are not enough of these shear walls available, we then have to look at other options such as Steel Moment Frames, that can easily be $10k per story or Simpson Strong Walls that are much more expensive than conventional shear walls. A lot of the time
slight tweaks to the window openings and obtain the required walls without detracting from the architect’s vision.
The Value Engineering does not stop at the end of the design process. Value Engineering should continue all the way through the rough frame portion of construction. One way to save is for the engineer to be open minded in his or her responses to field questions or suggestions from the contractor. The contractor may have a better way to frame an area or transfer loads that could save significant time and money, but it must be approved by the Engineer of Record. Being open minded to these ideas will help economize the final product. It is also very important to respond to contractor questions quickly because time is money in the field and a lagging engineer can definitely hold up the process.
SketchUp Basecamp 2018
SketchUp Basecamp 2018
SketchUp Basecamp 2018
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Structurally Insulated Panels in Tahoe?
A Look Into SIPs from Various Perspectives
No Content From Previous EE Backup
Perspective from the Architect, Engineer and Contractor concerning utilizing SIP (Structurally Insulated Panels) on a project in Martis Camp (Truckee, CA)
SketchUp 3D Basecamp 2016
Integrating Structural Engineering with SketchUp
Integrating Structural Engineering with SketchUp
Along with Nick Sonder, Zachary Engineering was asked to present at the annual SketchUp 3D Basecamp in Colorado Spring in June of 2016. In front of standing room only crowd in June of 2016, Zachary Engineering and Nick Sonder spoke about the processes utilized when it comes to integrating Nick Sonder’s SketchUp Wizardy
into a complete set of structural plans using both SketchUp and LayOut. “Integrating Structural Engineering with SketchUp” was one of nearly
two dozen presentations that took place at 3D Basecamp in Steamboat Springs, Colorado.
Watch the full 1-hour presentation here.
As part of the presentation, a video compilation of one of the latest coordinated projects with Nick Sonder located in Martis Camp was created. Watch it here!
