If the deck doubles as a porch it needs to be able to support no more than 80 psf.
Post footings for extended roof in bedrock.
Footings on bedrock and deck plan by.
When you pour concrete footings hold the cardboard concrete form tube about 12 in.
Building codes have a few things to say about foundation footings.
The buried post footing this footing method involves pouring a concrete pad at least 12 thick at the base of your hole.
Our building safety dept requires that if you hit bedrock then the entire footprint of the house must rest on bedrock.
Is it necessary to excavate the rock to achieve the 42.
Specifically we have a case where bedrock is say 24 below grade and minimum frost depth of 42 below grade.
The footing supports a poured in place or pre cast concrete pier which in turn supports a post.
The placement of footings and piers is dependent upon the post locations which in turn are determined by the beam and rafter spans.
How to get a solid frost proof footing.
Most deck roofs require separate footings from the deck to support the weight of the roof throughout the seasons.
Improperly built foundation footings unlike poorly installed gutters or gapped hardwood flooring can eventually bring down the house.
Excavate as before but instead of using gravel drill into the side of the footing and epoxy steel dowels into it then place concrete to extend the footing out to the proper width.
Editor rich bergman footings on bedrock are as solid as they can possibly be.
In weaker soils you have to augment the footing itself with steel and concrete.
Dig down until you reach the bedrock.
Next set a pressure treated wood support post rated for ground contact on top of the pad and backfill the soil into the hole.
Pick up some rolls of tyvec house wrap cheaper than fast foot use 2x4 s for your footing boards get it nice and level then attach your tyvec to the 2x s make sure the tyvec drops down either side and runs across the bedrock.
They don t want half the house on dirt and the other half on rock.
Drill holes and epoxy steel into the footing to tie the wall to the footing and then form and cast the wall.
Up from the bottom of the footing.
For deck roof posts dig holes for the roof posts and pour cement to keep them secure.
Do this by nailing the sides of the tube to the center of a tic tac toe grid of 2x4s at the top of the hole.
If you really wanted to do more you could jack hammer away some of the rock to create a bit of a hole for the cement to form into.
Then dump concrete through the tube into the bottom of the hole.
They also require two 5 s continuous around the perimeter footings as well.
Porch decks also require larger footings than deck footings.
For more about pouring footings see pouring footings piers.
Nobody can deny the need for a good house foundation.