Reinforced Concrete Floor

therefore need to calculate for live and dead loads including the type of reinforcement if it required.

therefore is not appropriate-is it?

need to calculate for live and dead loads : Need to. Well do it then.

including the type of reinforcement if it required.: If at all you need reinforcing say:

• On sinking backfill on which your floor will rest
• On Backfill likelyto sink due to water seeping into it(see "CRACKING Floor"posts)
• You Put Heavy Machinery on it
• Concentrate heavy storageloads on it.

Sounds like a load of BS to me.

Reinforce the whole thing to 2x the live load distributed to the heaviest spot---- or put it in and dig it up a few times.

Design floor live load (Uniform Building Code - USA) is 40 lbs/sf. A 4" thick slab on grade can easily handle this. To control shrinkage cracks install a 6"x6" welded wire mesh in the center of the slab. If you anticipate higher loading (heavy machinery) install #5 horizontal steel reinforcing bars at 12" on center in each direction, 2" above the bottom of the slab. To be very conservative use a 6" slab and #4 rebar. Compact the subsoil and place at least 4" of drain rock below the slab. If this is a living space, install a 6 mil PVC vapor barrier beneath the slab over the drain rock. You say the perimeter foundation is UNREINFORCED? That's a serious problem. You can correct this by thickening the new slab (12"x12") along the perimeter of the existing footing. Drill and epoxy 18" long horizontal #4 steel rebar dowels at 24" on center into the existing footing - 6" from the top of the slab. Lay one or two continuous #4 steel reinforcing bar 2" above the bottom of the thickened slab. The dowels will lock the new footing into the old footing.

Hire a local civil engineer and save yourself time, money and grief.

I am a Civil Engineer registered in California, the last response is the best one. You need to supply more information about the design and function/use of the building. The load is dependant upon the usage, there are use safety factors to consider. There are foundation bearing and settlement considerations. Also, there may be siesmic design requirements. The UBC has been replaced by the international code in the Western US (the UBC was a western US code, they don't make UBCs anymore, which should tell you something).

Thanks,

The building is 4 bedroom semi-detached .

Mass State Code

Minimun Unifrom Live Loads residential

Sleeping rooms 30 PSF

Other 60 PSF From 780 CMR Table 1606.1 sixth edition

(You must factor these loads)

The dead load for your basement will be the Weight of the concrete slab only

For your design load use Wu = 1.3 wd + 1.6 wl CMR 780 1616.3

If you have no settelment conserns you will not require reiforceing, no settelment not bending of the slab no bending no tension not need for TENSION REIFORCMENT.

What state are you in? The typical NE slab on grade

Cut min of 4"( frost protection)

Fill with crusded stone 3/4" to 1-1/2" (COMPACTED!!! this will reduce settelment)

A layer of compacted clean sand 6" (there is a volume loss from compaction, order most than you calc)

Min 4" slab

You don't have to reinforce a slab on grade it only holds what is on it and bending typically is not a problem because your foundation has been designed for the material the building is so much heavier that is the first to fail in the soil.

If you want ACI code on placing reinforcment I can give to you but simplely draw the moment diagram take Mmax uniform load Mmax @ L/2 and is (Wu L ^2) / 8

If this is grater than Mcr = (Fr*Ig)/yt

Fr= Modulus of rupture 7.5 Sqrt(Fc' typical 3000 to 4000 psi or 3-4 tsi)

use Fc'= 4000

Ig= Gross moment of initeria (for a slab of uniform thickness Ig is 1/12 * b*h^3

b is width h is thickness)

Yt is half the thickness (for uniform double semetric shape like a slab )

If Mcr>Mu increase the thickness of the slab and recalc

Don't forget about shrinkage and creep

thanks,your contributions were useful.

<Sleeping rooms 30 PSF>

Live Loads in Massachussets?

2 persons necking could be 400lbs -(per Sq foot or less)

There may be disaster!!

Hilarious!!