Footing Size For Porch Roof

Sizing deck footings assuming a minimum soil bearing capacity of 1 500 psf 8 inch diameter concrete piers bearing on square footings measuring 2 feet on a side and 9 to 11 inches thick are adequate for most single story decks where beams are spaced 14 feet apart or less and joist spans are 14 feet or less see table below.

Footing size for porch roof.

You can multiply this area by 55 lbs per square foot loading to come up with 1 375 lbs total load. If you multiply the area of this section 5 x 5 you will get 25 square feet. Concrete footing forms like the quikcrete concrete form featured below are ideal for pouring concrete footings for porch foundations. My calculations came up with 15 3 4 in.

They usually come in 4 foot lengths are come in 8 10 or 12 inches in diameter. Footing size based on the original table 4 in the main body of dca 6 for the same sized deck calls for a 24 in. 12ft 2 sq x 1 d 4x8 10ft 2x8 24 o c. This means the example porch would need a 6 inch by 8 inch beam.

It should project on both sides no less than 2 inches. At a minimum the required footing size is 2 6 squared or 2 6 x2 6 which will yield 6 25 square foot area of footing. All construction shall comply with international residential code 2. It will take a few minutes to do the tributary area calculations and then match them up to table b3 but the time will be well worth the effort given the labor savings when digging the footings.

Be sure to have your joist span calculations ready to enter for an accurate reading and check out our concrete calculator to determine the size of your footings total linear feet of railing joist length 6 7 8 9 10 11 12 13 14 15 16. Diameter center footing size and table b3 calls for a 16 in. That is assuming you are using a 4x4 which is 3 5 square. Calculate the initial value for d then round it up to the nearest inch.

Porch depth footing size beam size max beam span rafter size post size 10ft 18 sq x 1 d 4x8 10ft 2x6 24 o c. You can get away with usually a 15 x15 base and then at least 6 thick so you don t crack the deck footing. In the example d calculates to 7 75. Once you know the total load you can use the chart below to determine the footing size for your soil conditions.

All wood to be 2 douglas fir or better. For a quick and dirty concrete foundation this method can do the trick. The 15 000 pounds given above obviously does not include the weight of the footing itself so we need to calculate the weight of the concrete and add it to the total load of 15 000 lbs.