Expert: Bruce E. Johnson - 1/4/2010

Question
Hi Bruce,

I have a 2 story modular home built in 1986.  The support columns in the basement are roughly 8 feet apart.  I would like to move or possibly eliminate the first column in from the end of the house.  Do I have any options?

Thanks.

Ray

Answer
Hi Ray, Chances are that (a) the columns support a main beam that consists of the two inner rim joists of the floor system being attached together at the time the two halves of the home were placed on the foundation.  I will venture a guess that your floor system is made up of 2x8 joists?  That would explain the 8 foot spacing of the columns. (b) If your house sits on top of a post and beam setup,(the floor joists actually sitting on a beam that is supported by your lally columns) then I would need to know what size the beam is to make a qualified judgement as to the spans the beam can safely support.  If your home is set up according to (a) above then you can possibly add a beam below the joists to increase the span between columns.  In other words, if you want to increase the span to 12 feet you can put in a 4x10 beam below the joists and move your column four feet.  However, some architects and engineers only provide small internal footings below the concrete floor slab centered underneath the columns .  By moving a column you may be losing the built-in support of the foundation in this area.  Your new column location may only be sitting on a 4" slab which may or may not be able to hold up the concentrated load in the new location. There may be other alternatives to your dilemma, if the modular manufacturer is still in business you might be able to contact them regarding the spans of your joists and beams.  Also you may have the original set of blueprints that came with the house, showing how your foundation was constructed and if the lally columns are sitting on a strip footing below the slab or on individual support pads.  I hope this information helps, please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com