Originally Posted By: bking This post was automatically imported from our archived forum.
Would you agree with this rule of thumb for beam supports?
(Assume fairly long spans for this discussion and double thick LVL’s)
I think all LVL beams in the ceiling that support 2nd floor loads with roof point loads on them too, should have a minimum of three 2x4's supporting each end with a minimum of 3 inch bearing surface.
I frequently see only two 2x4's on some beam ends.
Sometimes these beams even have another beam connected at mid span.
I would think that two 2x4's would maybe only be good if the beam was only for ceiling joists with no attic storage above and not very long span.
I think that even four or more 2x4's is necessary in many cases.
Originally Posted By: rcloyd This post was automatically imported from our archived forum.
Bruce:
The maximum number of jack studs required to support a girder (beam) when the girder supports two floor loads in a building 36 ft. wide is two (2).
Per IRC 502.5(2). The type of beam LVL, Wood, steel is not a factor in the number of jack studs.
Originally Posted By: bking This post was automatically imported from our archived forum.
I don’t have the code books…
please reread orig post, beam with roof loads also and of course ceiling joist loads from usually two sides also plus the floor load. Then if another beam ties into the one in question, you have some major loads with all of the above.
The reason for using LVL in this example is due to its purpose of long spans and higher loads. If a double or even triple 2x12 is used for a beam then I agree that 2 studs will work since the loads that dimensional lumber can handle are much lower than LVL.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
The model code provisions like those in the IRC relate to conventional lumber framing … and do NOT apply to engineered lumber, like LVL beams and girders, which have higher capacities and heavier support load requirements.
Check out the APA standards on LVL's at www.apawood.org (simple registration for downloads), or check some of the various LVL manufacturer's sites (like TrusJoist or GP) for additional info and the support requirements.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: R. Michael Gray, P.E. This post was automatically imported from our archived forum.
There is no simple straight-forward answer to your question. The support required depends on the loads to be transferred. Generally any floor beam that supports roof loads should be engineered and that also goes for any beam support.
Having said that, consider that wood is actually stronger than steel in compression when the weights of the steel and wood are equal.
The bottom line is that if you are uncomfortable recommend they consult an engineer.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
There is a big difference between “conventional lumber framing” and “engineered lumber framing”.
For conventional framing with typical solid sawn wood members, there are very prescriptive requirements in model building codes like the IRC related to allowable spans and suppport requirements for things like wood joists/rafters and wood headers/girders. Those prescriptive provisions are fairly easy to apply for someone who understands framing.
However, those prescriptive model code provisions can not be applied to engineered lumber (like LVL's and I-Joists) which requires a case-by-case evaluation due to the higher capacity and special requirements.
For engineered lumber, I think the best thing for an HI to do is look for visual indications of problems, and defer to an SE as Mike noted for anything beyond that.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: R. Michael Gray, P.E. This post was automatically imported from our archived forum.
I agree with Robert completely. As a home inspector you are making a performance inspection. That is, how well is it working? If the support has been fully loaded in the past, which is normally the case in a resale house, and there is no apprent performance issue, it is probably okay even if it was not done to the book.
No one should expoect you to perform engineering work or be be familiar with the manufacturers specs of every piece of engineered lumber. Just concentrate on whether there are any visually apparent performance problems and use a little common sense and you should be okay.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
R. Michael Gray, P.E. wrote:
If the support has been fully loaded in the past, which is normally the case in a resale house, and there is no apparent performance issue, it is probably okay even if it was not done to the book.
I agree with ya in general, except for that one. A fully loaded structure that was not done correctly can just barely support that load, and at the same time weaken the structure to the point where the next full load will cause a collapse.
I have seen it first hand, and in one case after doing some calculations warned of a probable collapse of some main framing members in a house ... even though it had been previously fully loaded. Part of a house house collapsed about 2 weeks after I issued that report. Fortunately, the house was condemned and posted, so nobody was there at the time it collapsed.
I often say that ... "the length of time any structural element has been standing has absolutely nothing to do with it being adequate or safe". There is a brutal reality to that opinion.
bking wrote:
Framers, call your lumber dealer and ask for help !
They should also call the person responsible for the design to clarify anything that is unclear. As a designer and municipal inspector also, I see too many framing contractors just winging it on the engineered lumber. They usually get the point after changes and delays.
Just my opinion and 2-nickels ... 
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: R. Michael Gray, P.E. This post was automatically imported from our archived forum.
Robert O’Connor, PE wrote:
I often say that ... "the length of time any structural element has been standing has absolutely nothing to do with it being adequate or safe". There is a brutal reality to that opinion.
I guess we will just have to disagree. These are visual inspections and the question is not a matter of being absolutely certain as to the safety or adequacy of a structural member or arrangement. The question is what is a generally reliable basis for forming an opinion. If a structural member has, in effect, been load tested, I consider that fact to normally be a reliable basis for forming an opinion. If we reject load testing in favor of calculations that makes no sense to me. Calculations are also based on load-testing; specifically testing is required to obtain reliable engineering properties for use in making calculations. Modern span tables for solid sawn structural lumber are based on empirical performance of rafters and joists in the field.
How well a member has performed in the past, especially if it has been fully loaded, is an important and generally reliable indicator of future performance. That is not to say that nothing can go wrong or that it does not need to be looked at carefully; but to ignore performance data will, in the long run, create more problems than it will solve.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
R. Michael Gray, P.E. wrote:
These are visual inspections and the question is not a matter of being absolutely certain as to the safety or adequacy of a structural member or arrangement. The question is what is a generally reliable basis for forming an opinion. If a structural member has, in effect, been load tested, I consider that fact to normally be a reliable basis for forming an opinion.
Well said Mike, and I agree about an SE opinion based on a visual observation. But I think as one professional to another, we will have to agree to disagree on past loading being a reliable basis for structural capacity.
Industry standards for load testing structural elements calls for applied test loads to be in the range of 1-1/2 to 2 times the maximum design load. That is about what the factor of safety in calculations normally is to account for things like variations in material properties, installation imperfections, deterioration of materials, and uncertainties in the loads. In service loads will typically never even reach design level loads, and even then that service/design loading by itself is not a valid load test.
As engineers we can formulate professional opinions on the safety of a structure based on visual observations, knowledge of design and construction requirements, review of design documents, performance of similar structures, past loading history, and other factors. But even when I am doing just a visual observation, I am thinking about rough loads/capacities and rules of thumb ... and where something rubs me the wrong way I will recommend/do more detailed evaluations.
But the point here is really that a home inspector should not be making an assessment or offering an opinion on structural safety or load capacity based on visual observations, without the training and experience necessary to make that call ... no matter how long something has been (barely?) standing ... or that can be a fatal mistake.
Just my opinions and 2-nickels ... 
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
