I am finishing up a 8 x 12 screened porch that has two of its sides
attached to the house. That leaves one corner that needs support. The
porch is inset into the corner or the house (one story) so the weight
of the roof and the porch will be bearing on the column. It is about
9' off the ground. The plan was to have a mason build a 18" x 18"
granite column to support this corner. I want to use granite to match
the foundation which is granite. A builder friend of recently told me
that the granite column really isn't strong enough to hold up the porch
and that I should use a 4" steel post because it would be stronger.
For me a steel post is not acceptable because of the looks unless it it
encased. Anyway, my feeling is that a properly built stone column is
WAY more than adequate but before I proceed I though I would check and
see if this builders argument has any merit or should I just dismiss it
as bad advice.
Is there anyone here who might have some insight into this question?
Your thoughts would be much appreciated.
Depends on how he was planning on building it. If you want granite boulders,
round rocks will not stack strong enough to hold any weight. If the stones
are to be cut and dressed, not veneer but solid masonry, it should hold most
If you're using round rock, there's nothing wrong with using a steel column
inside and using the round rock as a veneer. 18" - 4" = 16"/2 = 8" so you
could use rocks up to 8" in size. If this is significantly smaller than
the granite you're trying to match, you're stuck.
First, you need to calculate how much weight is involved.
If you go with masonry, you probably need to get a structural engineer
or an architect to do some calculations, and find a mason that will
comply with the specifications they give. I.e., if the rock is strong
enough, but the mortar isn't, you may have problems.
An alternative might be to use a steel post, framed with rock. You can
look up how much weight a given steel post will support, and the framing
rock would not be structural.
You should also give careful consideration to what will be supporting
this column; you will need some kind of foundation that meets code. The
same goes for the top of the column; you likely will need some sort of
plate to spread the load.
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