Wouldn't you like that pass-through from the kitchen to the dining room? A new sliding door or bigger window? How can you go about finding the right beam when you want to remove a section of wall in your house?
First a few words of caution. Structural modifications without the consultation of a structural engineer or your building department are never recommended. Possible structural implications go beyond the beam itself and include but are not limited to; affecting the roof framing design and adequate load path to the soil, foundation or raised crawl space floor issues, the need of additional support under new beams, and new deficiencies created if lateral bracing and shear walls are removed from existing structures in high seismic or wind regions. Doing structural modifications without permits could lead to obstacles during the future sale of the property. If the building department finds out you are doing unpermitted revisions, penalties could ensue. So, check with your local building official before doing a remodel that entails structural modifications.
With that said, if you are a do-it-yourselfer type and want to get a feel for what your project will entail, the first step is to determine if the wall you are removing is a structural bearing wall (i.e., if the wall is removed will the upper structure collapse or sag?). If you do not have structural plans of the house this may require you to climb up in the attic to observe the roof framing. Many roofs are framed with lumber as the upper rafters with struts coming down onto ceiling joists, called a stick framed roof or conventional/compression framed roof. With these systems, usually both the interior and exterior walls aid in supporting the roof and ceiling load. In addition, the ceiling joists may act as collar ties in tension to prevent the wall from pushing out and the roof sagging....so do not cut the ceiling joists! Now if you have such a framing scenario, assume the wall you are taking out is a bearing wall, especially if it has upper rafter struts landing near it! And of course, all exterior walls are deemed as bearing walls. See figure below:
Another way to frame roofs is to use prefabricated metal plate connected trusses. Truss designers will typically always use the exterior walls as bearing points, but if the truss stresses and/or deflection due to longer spans or loads gets too high, then midway bearing support will be used. See figure below:
Typically truss manufacturers will put additional tags on the bottom of trusses to tell framers where additional bearing support needs to be. So, if you see such tags, then the wall below is most likely a bearing wall. But if you see a gap between the truss and the wall, it is reasonable to say that wall is nonbearing and can be removed, without any beam needed at all. See figure below:
Now for sizing the beam. Once you understand your roof system, the next step is to determine what the beam needs to support once you remove the wall. For simplicity we will deal with a single-story home with a conventionally framed roof with no attic storage or habitable space as shown below:
Weyerhaeuser’s Specifier’s Guide for Beams, Headers, and Columns, TJ-9000 and TJ-9020 (West Coast Region) can help a homeowner justify which beam product to consider using.
Link to our guides:
One will notice Weyerhaeuser has 3 Trus Joist beam technologies to choose from. 1.55E TimberStrand LSL is the most economical beam to use and is offered in 1.75- and 3.5-inch widths. Depths range from 9.5 inches up to 16 inches in most markets. Microllam LVL is only available in 1.75” widths at depths starting at 5.5 inches up to 24 inches deep depending on the market. Microllam LVL is almost 30% stiffer than 1.5E TimberStrand LSL. Depths greater than 16” must be at least a 2-ply built-up member (i.e. 3.5” wide). The 3rd beam we manufacture is 2.0E Parallam PSL (2.2E Parallam PSL in western states). The higher the “E” value, the stiffer the beam which results in less deflection under load. TimberStrand LSL is ideal for shorter spans while Microllam LVL and Parallam PSL with their greater stiffness will span farther with less deflection. The Specifier’s Guide for Beams, Headers, and Columns contains load tables for each of the beam products we produce and are used similarly as demonstrated in our example.
Typically, the stiffer the beam material, the smaller section that can be used. Parallam PSL is offered in solid 3.5, 5.25, and 7 inch widths from 9 1/2 to 18 inch deep. Wide solid section beams are easier to install if the beam is not too heavy for the installer. As an option, Microllam LVL or 1.75 inch wide TimberStrand LSL could be an option to build up a wider beam, therefore lighter for the installer.
For this dialogue we will always assume the beam will be installed below the roof framing and ceiling members (installing beams up in attics spaces requires further structural consider). Also recommend is maintaining the existing top plate of the wall section being removed since the double top plates acts like a chord tie for overall structural integrity. If removal of the top plates is desired to gain 3" in beam height, then metal framing straps from beams ends to wall sections is prudent.
Now moving forward with information in our beam guides, the pages dedicated to non-snow roof low tables are applicable for our considerations. Areas with snow considerations we highly recommend you consult with your building department to know what snow load requirements exist and then use the snow roof load tables.
Load tables are published for each beam product and size with limitation based on how far it will span and under required deflection characteristics in pounds per lineal foot capacity (PLF) which is simply the continuous cumulative in pound loading along the beam that the product can handle for a given span. It does not include or consider any point loads from other structural beam elements.
A good recommendation is to always use the total load deflection limits based on deflection characteristics of L/240 to prevent gypsum board finish cracking and serviceability. For example, if the beam is spanning 10 foot, when the span L is converted to inches, the deflection controlling load limit will be capped at 120 / 240 ratio which equals 0.5 inches maximum.
Now for that beam design, on page 22 in guide TJ-9020 for a proposed new 10-foot spanning beam span with a recommended deflection criterion of L/240, a 3.5-inch-wide x 9.5-inch deep Parallam PSL 2.2E can support up to 1,115 pounds per lineal foot (PLF). See guide’s snapshot of chart below:
But now comes the tricky part in knowing what the demand loading is onto that beam based on your roof geometry. A simple and conservative way to ascertain what those values are is to simply divide the overall length of the roof from exterior wall to opposite exterior wall and multiply by 5/8 (0.625).
For example, if you had a 24-foot-wide roof (House width below) and multiply by 0.625 you get 15 feet. This dimension is typically referred to as tributary width which in turn gets multiplied times the pounds per square foot (PSF) dead (i.e., self-weight) plus the transient live load of the roof as designed per code. See figure below:
In areas with no snow load, the worst-case live load would be 20 PSF. While typical dead loads for composition shingle roofs are 15 PSF, while standard roof tile could be considered at 20 PSF. For this example, we will use 15 PSF dead + 20 PSF live load, which is equal to 35 PSF total load consideration. Then that tributary of 15 feet would get multiplied times this 35 PSF yielding a 525 pounds per lineal foot (PLF) demand on a beam that would support a 24ft wide roof. This is the number you would compare to the capacity listed in the beam guide. For our example, since 525 PLF is less than the beams capacity at 1,115 PLF, then the 3.5 x 9.5 Parallam PSL would be a solution to span 10 feet. The guide charts will also list minimum end bearing requirements which will typically be made up of double 2x trimmers or solid posts.
Note the example above was assuming an interior application.
If the beam is in an exterior wall, as noted in RED in figure below:
One would typically use a ½ (0.5) multiplier of the house width plus any additional roof overhang framing to obtain the tributary width value. For example, say 1.5 ft overhang is added to the 24 feet x 0.5 tributary equaling 13.5 ft total tributary. Now the demand value would be 473 PLF which is still below the 1,115 PLF beam capacity. So, the same beam is still structurally adequate.
Now to make sizing a beam easier for you, we also offer a simple Beam and Header Sizing Calculator. Simply click on the model that represents the beam or header you are trying to size and select the appropriate parameters from drop down menus.
In addition, for those who wish to try our free online design software, give ForteWeb a go.
Once again, structural modifications without the consultation of a structural engineer or your building department is never recommended. An engineer may be able to better justify the load path to the beam and potentially size a more economical size. The tools we have demonstrated assume the beams are uniformly loaded along their length. For more complex loading situations hiring an engineer is a must. In addition, an engineer can provide details for beam supports to assure the loads are safely transferred to the ground.
Hope this helps the homeowner wishing to do a little remodel. If you still need further assistance you can always contact us at our technical support number 1-888-453-8358 or email firstname.lastname@example.org.