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Architectural Detail Experts | A Blog by Worthington Millwork

5 Biggest Myths about Load Bearing Structural Porch Columns

Posted by Holli McRae on 1/29/13 1:49 PM

Porch Columns

1 – Because my porch columns are structural it should hold up my roof. 

Not necessarily!  Worthington’s fiberglass columns are structural and it is always important to ask a structural engineer whether or not the load bearing capacity of our column will exceed the weight of your roof.  These calculations should also figure in the weight of snow, rain, etc. that could potentially add weight to what is figured in the project drawings.  Too much weight could equal problems in the future!

2 – I can align the header of my roofline anywhere on the top of column and the column will bear the load. 

Definitely not; and we get this question a lot!  In all load bearing applications the header must be placed in the center of the column.  When the header (no matter what the width) is not centered on the top of the column shaft the load capacity of the column shaft is greatly reduced.  This is not recommended and there is not an accurate way to gauge exactly what the column will hold when it is loaded this way.

3 – Split columns, once reassembled, are structural columns.  

False!  Split columns are mainly used in two applications: (1) to act as a half column (a.k.a. pilaster) against the wall or (2) to surround a structural support.  Though once reassembled they may have some structural load capacity to them; the amount of load capacity of the porch column has not been formally tested and thus cannot be guaranteed.  Also, this application defeats the purpose of purchasing a structural column.  Why have the columns split for a structural application when they are already structural to begin with?

4 – In a free standing or pergola application the column will hold up my pergola beams. 

Though this statement is somewhat true as the fiberglass column will hold up the pergola there is a big exception.  The fiberglass columns DO NOT support lateral movement.  In situations that could be in windy areas or even leaning on the free standing pergola this could cause the entire system to fall.  A structural support, such a pressure treat pine wood post or a steel support, must be installed in a footer below.  The structural support will run up through the column and connect to the pergola header above.  This will prevent the lateral movement and also support the pergola system as well.

5 – I don’t have to trim my column at the bottom to accommodate the slope of my porch.  

You might not have to if the slope of your porch is not too drastic.  However, for the same reason as misconception #2 above; you need to make sure that the load is distributed evenly across the bottom of the porch column.  In cases where you have a larger diameter column this is more of a prevalent occurrence as the slope of the porch is over a longer distance of the bottom of the column.  If the bottom of the column is not adjusted you could be bearing most (or all) of the load on one side of the column.

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