concrete porch

3927 Views 4 Replies 3 Participants Last post by Wildie, Jul 16, 2009

xenophus

Discussion Starter · Jul 15, 2009

I want to add a concrete porch to my house. I think 4" depth and 7' x 12'. I'll have atleast two posts to support the roof and tied house with ledger board. Can I just tamp and pour or do I need footers or added depth to account for frost? Live in WV.

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stadry

· #2 · Jul 15, 2009 (Edited)

your local bldg code'll govern footing depth,,, never underestimate frost :yes: you'll probably need a contraction/construction jnt 1/2way across the slab resulting in 2 pieces of conc approx 7' x 6',,, the deck'd be supported by your compact'd fill & the top of the fnd walls,,, expansion jnt next to the house
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Wildie

· #3 · Jul 16, 2009 (Edited)

I have a concrete porch that is 8X13 and its barely usable. I wish it were at least 10X13.
Recently, I replaced the aluminum canopy with a wood framed shed roof.
The porch foundation was constructed by digging a 8" trench down down 24". A form was built 24" above the ground, then concrete was poured.....
This foundation wasn't adequate to support the new roof. To resolve this I dug down at the corners to the 48" level (our frost level here) and poured footings.
Once the footings were set I poured piers using Sono tubes.
Snow load is a major factor here, so I built the shed roof to support 40 lbs/s.f.
The roof is supported by 6X6 PT posts. A beam laminated from 3, 2X10's spans between the posts.
Our building code would have allowed 2X6 rafters (span 8') but i installed 2X8's to be on the safe side.
The ledger board was installed just under the house soffit using 1/2"X4" lag screws driven into the wall studs. On 16" centers.
The rafters were supported by hangers, rather than being laid on top, to give maximum slope to the roof.

I used hurricane clips to anchor the rafters to the beam, as protection against 'lift' is required by our building code.
The total project cost me $1,650 for material and the roofers labor.

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xenophus

Discussion Starter · #4 · Jul 16, 2009

Thanks for the quick response everyone, and I am now considering making it slightly bigger although we do have another porch on the side for leisure.

I was wondering about the footers.........is that just under the pillars or do you mean continuously run under the perimeter of the slab? I'm not planning to ever enclose that porch so think just under the posts is fine. Also, is there some way I have to tie the post footers into the slab or do I just pour everything at the same time and no need for added rebar in the footers to extend up into slab? Then, if I have two footers along front, should I put two footers on back near house foundation just to help keep slab anchored level?
Sorry for all the questions. Just moved here from south TX and there we don't have all this frostheave issue.

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Wildie

· #5 · Jul 16, 2009

It seems that you are thinking about a floating slab. These are used often as the slab rises and falls with the frost.
However, with a roof that is attached to a building, the last thing that you want is to have it rising and falling.
I would suggest that you would install footings below the frost level and piers for each post.
The piers would be constructed using Sono tubes filled with cement. The posts would be fastened to the piers with Simpson fasteners ( http://store.qualitydist.net/sst-abu66.html )
The slab would be poured in such a manner, that it can 'float' without interference from the piers.

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