calculate load bearing

[RCPinard]

Greetings all. We are trying to start a renovation project. The current structure is a 24'x40' ranch. We want to A) remove the 12/12 gable roof, B)add a second floor C)add a gambrel roof.

Questions:
How do I determine the load bearing capability of the existing foundations/walls?
What method(s) is/are there to shore up the existing structure if the need presents itself?
How can this be accomplished with 5 adults living in the structure?
We don't plan to put many walls on the second floor, will this reduce the dead load?
Would we be better served by redesigning the gambrel to accomodate the 'second floor' with a loft bedroom?

 

[rlflower]

OK, a few questions of my own:

1.) Are you the designer/ Architect, owner, or and engineer? I guess I just need to know who I am talking to. I am an engineer myself.

2.) Is this to be a full second floor, or partial?

3.) Do you intend to have all (or most) of the second floor and roof supported on the exisitng perimeter walls, or is there additional support in the interior?

4.) Just how old is the existing structure (take a guess)?

5.) In what condition is the existing walls? Termite, dryrot damage? Are the existing walls constructed in a conventional manner (i. e., 2 x studs at 16" o. c. with a continuous double 2 x top plate)?

One thing is very likely: you may well need to underpin the existing foundation system with concrete pads.

 

[RCPinard]

Thanks for the response!
1) Designer/owner (and desperatly trying to understand the whole process) Engineer - yes... of compuoter software/hardware, NOT very useful, except that it makes CAD a little easier to use. Capable of understanding technical details, but very fuzzy in this department. Wise enough to know when to say 'I don't understand, please explain it again/more fully.
2) Full. Partial floor built into the gambrel(1 bedroom, and if it will take it, a large walkin closet, or reading room.
3) This was the plan.
4) originally built in 1972
5) Everything SEEMS sound. I observe no dry rot or insect damage to any of the beams I can see(limited to the insulated but otherwise unfinished attic and underside of the floor from the basement) Cement foundation shows no cracks or heaves. There is a seepage issue, part of which I thin is that the gutters feed a downspout to asphalt for the driveway. I may be all wet (forgive the pun).

I have been *told* there is not much problem with adding on to what we currently have. I'd like to have the mathematical proofs, and understand them well enough to explain how I derived (fact A).
The one plan proposed by the only contracter we were able to contact at the time suggested adding a floor above the existing ceiling 'plate' to avoid having to re-run everything currently wired. He said this would carry the load added by the new walls and roof. This did NOT answer my question of 'what can the existing stucture take?'. Another one has said that if the building was built to code at the time it was built, it could take what we wanted to put on it. Original structure has 3 2x12 scabbed for the 'main' beam, 2x8 16"o.c. for floor joists. I have no idea what the framing for the walls was done with, assuming 2x4s for the most part. There are 5 walls perdendicular to the main beam, and 4 parallel to it (if that helps). Foundation is un-reinforced cement, 6" thick, 24'x40'. Slab underneath is anyone's guess. Just finished a -20 week, and it never got 'frosty', so I assume it's fairly thick.
I have contacted a local truss company to construct the roof trusses for us, as one design feature we wanted BADLY was to keep the area above the living room/ kitchen open as possible, with joists spanning (24') at about 14-16' W of the (endwall? Main envelope, 24' N-S oriented. This is an exterior wall) His design of the trusses supply 40psf l.l. and 8psf d.l. w/o the spanners, and 40psf l.l. 10spf d.l. with them. We plan on 2 ~15' walls parallel to the center floor beam, and 3 ~10' walls, 2 north of the floor beam, and 1 south of it. My understanding is that the new envelope would sit flush with the existing.
Today I found the parts of the code that define what each component provides toward deadload. Working on those now.

Thanks again for your patience and willingness to help!
Robin C. Pinard

 

[rlflower]

Thanks for your response. It helps me understand what you are attempting to do.

First of all, it sounds like you need either a licensed Architect or a licensed Engineer to review your work and approve it so that you can ligitimately present your proposal to the local city/ county for thier approval.

Yes, it costs money, but it is money well spent. It is not my place to judge your abilities, but believe me, you cannot afford to make common mistakes that can easily be avoided. Far too many owner/ builders try to save money by doing most or all of the work themselves; but they end up "eating it" in the end. By comparrison, you could imagine a novice fiddling with a computer and messing it all up - this is a simillar situation.

Contact a licensed civil engineer and establish a written contract with him/ her to answer these questions you have.

That being said, what you are attempting to do is not really a big deal, but it looks like you might have to supplement the existing perimeter footings with underpinning pads where the additional load is. But there are other problems to be addressed (as is the case with any project). One thing the engineer will have to address is lateral analysis, i.e., just how the building responds to a earthquake. This analysis will likely result in additional hardware in the walls - called "tiedowns" - to make the system work.

Spend your money and your time wisely; don't attempt to go further on this project without consulting an engineer or archiect. However, to save time and money, what you need to do at this point in the game is to solidify your design as much as possible before the engineer gets involved.

I metioned contacting an architect. The architect may be of great help to you for several reasons. The architect is not just a designer; he/ she serves as the person primarily responsible for the job, and manages the entire project.

Best of luck to you. By the by, you haven't told me where this project is (what city, state...). If your project is in Southern California, then possibly I can serve as your engineer.

-Richard L. Flower, P. E.

 

[RCPinard]

Thank you for yet another timely response. This reply will be kind of bass ackwards, but you'll get the idea...
We plan to do this in Massachusetts, and while you seem to be more than competent and knowledgable, I'm not willing to pay for travel expenses.
This is a very rural area, and 'architect' doesn't even show up in the phone book. I may decide to spread my search. And I AM trying to contact engineers, hence the posts here. My Uncle is an engineer for the state of Maine DOT, and I may ask him to 'proof' things for me, once I have a better grip on how this will all be done.
Having read the local code (a labor lasting 4 hours at the local library, ignoring everything NOT residential), there are no special requirements for earthquake, they seem to have more emphasis on snow and wind load. The truss maker has a design for us that exceeds code by 15% for both, while keeping dead load minimal. THOSE at least are being handled, however, these folks don't do the rest of the envelope... Again, my search continues.
The design is rock-solid firm, I have the floor plan etc on 1/4 graph, for handing over to a correct professional.
The houses to either side of ours, built as part of the same development project in the 70s have both had second floors added, and neither needed any reinforcement to the foundation, so I have my hopes in that department.
About the only things my husband and I plan to do on our own is paint/decorate, and maybe drill the joists/studs for running the electric.
And I get paid to mess up computers, yes I CAN imagine, I have to stretch to do 'dumb things' to computers all day.

Thank you again for your time and advice. Ever need something from the computer software department, give me a shout ;-)

 

[rlflower]

Hope you are still reading this thread...

You need a civil engineer that is licensed in your State. An architect licensed in your State might also be of help in refining you design, but the structural questions you have should be presented to an engineer.

That should narrow your search.