Re; Slab on Grade

[daniel nantell]

I see a lot of attached front porches ,, that pull away from the house and drop down a couple of inches, and need a lot of crack sealer . I though any part of the structure that was attached to house had to had a footing , so does porches have footing or is this just a slab on grade . Thanks

[Billy Stephens]

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I see a lot of attached front porches ,, that pull away from the house and drop down a couple of inches, and need a lot of crack sealer .
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I though any part of the structure that was attached to house had to had a footing , so does porches have footing or is this just a slab on grade . Thanks
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Daniel,

The short answer ( without seeing the property ) is if the home is slab on grade the poured porch is most likely the same .
* any piers on the porch would be required to be below your area's freeze depth.

Difference in compaction of the site soil and drainage of water away from the structure would be suspected causes.
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[Jerry Peck]

I though any part of the structure that was attached to house had to had a footing , so does porches have footing or is this just a slab on grade.


Depends.

Is the porch just an overhang with a slab for the floor, or is the porch a real porch with supporting columns and all?

If just an overhang with a slab, then the slab is on "attached to" the house.

If there are columns, and if the columns are poured with the porch slab, then the footing depth should be the same as the footings for the house.

If there are columns, and if the columns are separate from the porch slab, then the column footings should be the same depth as the footings for the house but the slab need not be.

However ... *for safety reasons* ... should the slab be attached to the house and have footings to the same depth - that answer is 'Yes, of course, that just makes common sense.' ;)

[Matt Fellman]

Around these parts I see a lot of sagging porches too and have just assumed that most have little or no footing.... and/or are placed on loose backfill which doesn't help the situation. The small gap between the two pours of concrete (foundation and porch) also make a great hideout for termites. I'd say 75% or more of termite problems I see are around porches or chimneys. It may be regional thing though.

[james hise]

Daniel,
There are usually two reasons for porch settlement. The first being the footing is settling due to improper soil preparation when the porch was built...meaning there may have been an over dig and the resulting backfill was an uncontrolled material and/ or not properly compacted.
Sometimes the porch will sink and rise over the season due to the footing not being below the frost line. The footing would need to be extended in this case.
Most often the cause of porch settlement is related to water accumulating in the vicinity, either from a defective downspout of gutter, a broken pipe under ground or improper grading allowing water to compromise the supporting soil.
For concrete porch slab settlement when just the top slab sinks toward the house usually the fill beneath the slab has settled. This can often be corrected with slabjacking. I've seen concrete porch slabs which were connect to the foundation block with rebar that still settled...ripping slots in the block as it settled.
Regards, jim Expert Basement Repair Company (http://www.expertbasementrepair.com)