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DT

In article , lid says...

Can you not beef up the foundation possibly? We have a crawl space, and
I was thinking that you should be able to add more piers to handle the
additional weight. Or is that wishful thinking?

Beefing up the present foundation would be extremely difficult if you are
talking about making the footers wider to lower the soil pressure to acceptable
levels. You would have to dig under the bottom of the footers and pour
additional concrete, yet maintain the undisturbed soil under the new concrete.

The foundation requirements for a simple two story house are not *necessarily*
any higher than a single story house, as long as the present foundations meet
the code. We went over this when I designed my project, and we simply had to
inspect the footers to determine that they were a full 16" wide for our soil
type. There was no higher spec for a foundation to support a two story house.
The concern would be that your present foundation doesn't meet the code at all,
and cannot handle the extra weight of the second story. I added 'necessarily'
because a non-standard two story design (like your proposal) can indeed require
different foundations.

You talked about adding piers, and that could be one solution, *providing* that
the piers are indeed handling the new loads. But most loads are in the
perimeter walls.

They also need to see if the bearing walls
will handle the extra load, along with details like roof construction
(trusses versus rafters). Remember, you're doubling the weight on your
foundation and lower level walls. If they can't handle it, you have a
showstopper problem.

Again, there are not necessarily higher requirements for the first floor
perimeter walls when they support upper floors - as long as the present walls
meet current codes. Current construction for lower walls uses 2x4's on 16"
centers with double top plates, whether there is one story or two. Headers over
large windows would need to be checked (in the past they were often framed with
lumber that would not adequately transfer the higher loads). But you must
determine if your present walls are to code. Interior load bearing walls can be
added if needed, although that may alter the layout of the first floor rooms
involved.

What if you want to only place a second floor over a portion of the
ranch house? Could you build piers/foundation to handle only that
portion of the house, and leave the remaining foundation as is?

That's certainly a possibility if I am picturing what you want to do. But it's
lots of digging in a confined space without being able to get machinery in to
do it. Lots of labor, and maybe hard to find someone willing to tackle it.

Then there's the whole issue of HVAC, electrical, etc. Do these
subsystems need to be overhauled for the extra load, or will your
furnace handle a new zone or two? That's the difference between $1K
for some new ducts or baseboards and $10K for a whole new system.

Agreed, and finding places to run new HVAC ducts can be quite a challenge in an
existing home. I had to tear out my brick chimney (it would have run through
the new upstairs bedroom) and replace it with a metal B vent chmney that could
be more easily made to jog around to get to a chase to run it through the
second floor.

Similarly, I had to give up part of one first floor bedroom to add a chase for
the heating ducts and returns.

Bottom line, get an engineer (or an engineering capable builder) out
to look over everything first and work up some numbers. There's no way
to estimate even to within a factor of 2 without knowing these things.

Yep.

--
Dennis