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-   -   Adding a second story to my ranch (http://www.diychatroom.com/f19/adding-second-story-my-ranch-37743/)

jpmildge 02-06-2009 09:03 AM

Adding a second story to my ranch
 
I have a 918 sf ranch built in 1952. We love our house, but desperatly need more space. I am thinking of adding a second story. The existing foundation is in good shape and consists of footers and 12"x16" concrete block. The exterior walls of the first story are 8"x16" cinder block. First of all, are the cinder block walls capable of supporting a second story? Secondly, is it possible to cantilever the second story, front and back.

Tom Struble 02-06-2009 10:15 AM

not sure about the cinder block maybe have to fill them solid? as far as the cantilever sure structurally can be done but you have to watch the setbacks from your property line

Michael Thomas 02-06-2009 12:15 PM

(Deleted)

Michael Thomas 02-06-2009 12:21 PM

It's by far easiest to cantilever in the direction of the existing joists, a true structural cantilever bearing significant weight and installed at right angles to the existing joists is an engineering project as you need to tie it back a substantial distance into the existing structure - it might be easier and cheaper to just scalp the structure at the top of the existing walls an build and entirely new floor structure to carry the load, putting stairs, bathrooms, etc exactly where you want them. Also consider extending the entire structure to the front or back (for example with a porch supporting the structure above), which also could pick up additional livable space on the first floor.

jpmildge 02-06-2009 01:05 PM

Yes the cantilever would be running in the direction of the existing joists. It seems after reading a few other posts that cantilevering is not going to be a problem. Still need to figure out whether or not the cinder blocks are going to be able to carry the load of a second story?

Brickie 02-06-2009 01:24 PM

Quote:

Originally Posted by strublesiding@optonline.n (Post 226078)
not sure about the cinder block maybe have to fill them solid?

Grout them solid, don't forget the rebar and anchor bolts:thumbsup:

Willie T 02-06-2009 08:41 PM

Go determine what you have for a footer before you continue too far with this. Chances are, you may have to significantly bolster the whole design right there.

concretemasonry 02-06-2009 08:51 PM

If you have 12x8x16 concrete block footings and the above grade walls are concrete block, the vertical load capacity is definitely not a question. - I have seen 20 story buildings built using 6" thick block walls.

You have two questions - the bearing capacity of the soil (can be determined by a few hand or machine borings) and the design of what the block walls are supporting.

A cantilever can be used to increase the area, but the second floor structural system must be designed for the cantilever.

Since you are cantilevering the second floor, forget about using any part of the existing roof, since it will be cheaper and faster to go with trusses

Dick

Willie T 02-06-2009 08:57 PM

Quote:

Originally Posted by concretemasonry (Post 226378)
If you have 12x8x16 concrete block footings and the above grade walls are concrete block, the vertical load capacity is definitely not a question. - I have seen 20 story buildings built using 6" thick block walls.

You have two questions - the bearing capacity of the soil (can be determined by a few hand or machine borings) and the design of what the block walls are supporting.

A cantilever can be used to increase the area, but the second floor structural system must be designed for the cantilever.

Since you are cantilevering the second floor, forget about using any part of the existing roof, since it will be cheaper and faster to go with trusses

Dick

Dick, You've been living in Brazil some, haven't you? :thumbsup:

jpmildge 02-08-2009 10:26 AM

Living in Brazil? Over my head I guess. Regarding the bearing capacity of the soil, how is this determined? Are there charts that will tell me bearing capacity for specific soil types? When the bearing capacity is determined, how will I know if my existing footer is ok or not?

jpmildge 02-08-2009 10:59 AM

Nevermind, found chart online.

concretemasonry 02-08-2009 11:19 AM

Wilie T -

Not living in Brazil, but visting many times including a lot of other places (Russia, India, etc.) with unique problems, solutions and traditions.

jpmildge -

In Brazil and some other countries, they build that way because their use of masonry is more advanced in many ways compared to the U.S. They essentially use U.S. standards (ACI 530) now and U.S. codes beginning in the 1970's, but are more progressive in the design, construction methods and inspection. - If they did not use masonry interior walls (even with a concrete frame) they would have a more limited market for the multi-story apartments.

You may have the charts on the soil, but the identification of types can be tricky. One danger is looking at the soil around the foundation/footing (usually backfill), since the natural soil under the footing is what is really important. Usually, footings are grossly oversized because of our prescriptive residential codes, so that should not be a problem if there has been no settlement or cracking in the past.

If you go ahead, you will ultimately have to use a professional to get a permit and he should be able to satisfy the requirements and it may just take a couple of hand samples without requiring a truck mounted rig.

Good luck.

Dick

nap 02-08-2009 11:25 AM

anybody think OP should hire an engineer to determine possibilities. His building department may even require a PE stamp on the design before issuing a permit.

concretemasonry 02-08-2009 01:11 PM

Undoubtedly, he will need a professional (Architect or Engineer) to sign the plans in the end. Depending on the area, either might be able to satisfy the local code people. - If they are fussy, they may require an Architect for the addition plans (fire separations, egress/access, etc.) and an engineer working with the architect on meeting the structural. With the exception of the soils/footings even an architect can do it since the structural requirements are by the prescriptive "book" that specifies the 2x sizes for the spans and cantilevers, etc.

Dick

jpmildge 02-08-2009 08:34 PM

Do you think that filling the cinder block with mortar and rebar is going to be nesesary or is this overkill? Just asking so that I have some background when talking to my eventual contractor.


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