Existing slab good enough?


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Old 12-09-05, 05:53 PM
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Existing slab good enough?

I have a 1968 single story house that came with a city permitted sunroom. Most neighboring houses in our tract are two story. The slab underneath the sunroom is about 6" thick and our regular slab is about 4" thick. I had hoped to tear out the aluminum walls one day and replace with wood frame 2 X 6's (thicker to get more insulation than with 2 X 4) walls. Three questions.

1. Is there a way I can tell if the new slab is properly attached to the existing slab?

2. How about a way to tell if the concrete is strong enough?

3. I will apply for a permit, but is there anything else I should know before replacing the walls?
 
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Old 12-13-05, 04:39 AM
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I don't think how your slab is "attached" to the house or it's quality will be the deciding factor. You local Inspections Dept. will probably be looking for a proper footer. I would also guess that being in earth quake country will require some extra foundation work.
 
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Old 12-13-05, 11:26 AM
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Existing slab good enough?

Tyger -

If the joint between the slabs is wide enough, you could probe with a very thin piece of sheet metal to determine if there may be a connection. If there is no connection you know for sure they are not tied together. If you hit an obstruction, they may or may not be tied together structurally. The bond of the two concrete slabs caused by two smooth ends abutting would not he considered a tie, especially in a seismic area.

You probably have no problem with the concrete strength, but you will need an engineer to come up with a design. Connecting two two structures (house and new framed enclosure) together takes special considerations if the slabs are not integral. To be safe, an engineer would have to assume they are not continuous.

Dick
 
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Old 12-13-05, 04:07 PM
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Assumming no connection ...

If I assume for a minute that there is not a connection between the existing slabs, would the best thing be to take out the newer slab? I am thinking this because it is "only" 12' by 16' but 6 inches deep. Is there some other way the room could be built with wood framing if the newer slab is not bonded to the old?
 
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Old 12-13-05, 07:13 PM
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Existing slab good enough?

The problem comes with connecting the house to the newly framed "room" or old sun porch if they are on separate foundations. This is especially important since you are in a seismic zone. It is not just a matter of holding up a roof.

What you do will depend on what you have and what an engineer would offer as options to pass code. There are simple seismic solutions that a local engineer would be familiar with that most people in other areas are not aware of.

You will need a signed plan to get a permit, so why not get help early so you can go in the best direction.

Dick
 
 

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