b'Anchoring Windows & Doors to Meet Design TapConsPressure RequirementsDesign Pressure Ratings ScrewsWindows and doors are usually selected for their structuralperformance characteristics based on local or state build-ing code requirements. The requirement changes based onwhat floor its installed on, what type of building its Wood Bucks must be anchored to openings with the same spacing as usedinstalled in, and what the weather characteristics are in the in laboratory tests. Window anchors, direct to the opening or to anparticular geographic area it is put into service. installed buck must also match the spacing used in laboratory tests.Obviously commercial grade windows, hurricane resistant Most manufacturers are happy to provide help inwindows and other higher structural requirementdetermining qualifications of their products for cer-conditions will designate a stronger window. tain applications. The storm resistant window requirement headed Residential Replacement codes specify certain Designnorth when the new International Residential Code Pressure (DP) Ratings. DP ratings are established by testingbegan mandating the window to pressures equal to 1.5 times the DP require-them all the way up ment. In other words, if a window is required to meet DP40,the eastern coast, then it is actually tested to 60psf. If a window is required tobut not all areas meet DP20, then it is tested to 30psf.need the same windows as South All building Codes require that the window or door unitFlorida.Fastener size and spacing be provided in instructionsCodes demand field and that they shall be calculated based on maximuminstallation to match loads and spacing used in tests. (ICC Code 1405.13.1)lab conditions Proper Anchor SpacingWindows must meet a design pressure requirement The window manufacturer should provide guidance for thethats determined by a number of factors, the most proper spacing as required in the ICC Code stated above.important of which is the geographic wind speed zone However, there is a formula that can be used to deliverthe house is in. acceptable spacing for residential installation. Number offasteners per side = Test Pressure x Width x Height xDesign pressure is the determining factor, and the .0001/4 A 36 x 60 window for a required 40 psf windwind zones dictate that pressure. Higher DP Ratings pressure: No. of fasteners = (P x W x H)(.0001)/4figures toare important in many areas of the country, not just be (40psf x 36 x 60)(.0001)/4 = 2.16 clips. Rounded up toSouth Florida the next higher number, install 3 fasteners starting 4-6Structures right along the U.S. coast have the tough- from top and bottom and no more than 16 between - or asest requirements. Homes a few miles inland generally specified in the test results. psf structural test pressure. have a lower design pressure, because the code For reference. minimum design pressure, structural testassumes that surrounding structures will provide pressure, and water resistance test pressures for the fivesome shelter from the wind.classes in pounds per square foot are shown here: Downtown areas might get an additional break Window & DoorDesign StructuralWater Resistancebecause of the shelter provided by tall buildings.Classes PressureTest PressureTest PressureLocal codes will usually be specific.Residential 15 22.5 2.86Anchoring in the home must match the mounting in the Light Commercial 25 37.5 3.75lab to duplicate the lab performance in the home and meet Commercial 30 45.0 4.50code requirements. Design pressure calculations can Heavy Commercial 40 60.0 6.00get extremely complex.Architectural 40 60.0 8.00Window Fitters Guide to Window Installation852020 AWDI, LLC Do not reproduce without permission'