I am building a deck, which will be supported by block & brick piers (cinder block wrapped with brick). Each pier will be 15 feet tall, filled with mortar and rebar for added strength. Each footer will be made with commercial grade, portland 5000psi ready-mixed concrete.

I've heard different advice on preparing the forms for the footers to hold all of this weight. I have rebarb cut to the size (3'x3'), and the rebar holders to keep the steel about 3 inches off the ground. Holes are dug, but they are uneven and can't be packed any futher.

1) how deep should this footer be? Remember my block & brick will be 2'x'2, so my current form allows an extra 6" on all sides.

2) can I fill in and even the surface depth with small gravels? If so, what steps need to be take to ensure the piers will not settle or shift?

3) what else should I know or do?

THANKS-first time ever post

 

Normally, a footing for your pier would be the size you propose if you have reasonably good soil. Normally, that would be 8" thick, but some would say 12" because you only have a 16x16 structural masonry column.

Because the piers are 15' high, they can add lateral load that could require a larger footing. Perhaps, the person designating the number and size of the rebars in the piers could size the footing for your project, because it is a little unusual. Much depends on the lateral stability and types of connections and bracing. You may also need "L" bars to lap/tie the footing steel with the pier steel. A 16x16 column that is 15' high can be subjects to many loads that can not be determined for the information provided.

You NEVER use mortar to fill reinforced block. Concrete is also NOT acceptable because of the aggregate size and inability to fill completely and bond the steel to the block (your loadbearning form). You use grout and place it in lifts (4' or so) to allow complete filling and time for consolidation. Each lift should be rodded or vibrated into the lower lift.

If you have firm natural soil, pour on it and let the concrete fill the irregulaties. Concrete on firm natural soil is always better then concrete on compacted fill or coarse rock fill.

Dick

 

What you have we call in the trades,"free standing structure" The thickness is not nearly as important as the width of the footer. As a general contractor 28 years,mason first trade what you have is actually a block veniered chimmney brick faced. 8" thick foote is fine with rebar. No stone under footer! Pour heavery to level footer pads. The footer should be min 12" away from finish walls because a peir needs more stabilty for latteral shift. your deck is to light in weight for down pressure stability. The peir coud drag the deck out. Now as far as rebar and grouting. Are you going to pour after the block is up or I would "grout as you go I like portland cement, lime and sand to grout. Its real conc whitout the stone. If you use portland cement for grout you can actually use that for your footer and add 3/4 to 1" stone in the mix batch and now its concrete. Way cheaper than the builders store baby bags. I would add the rebar as you lay up the block and add tied rebar togther on lifts. If you have to stop for the day make sure more rebar is sticking out for the next day ties. Stop in the middle of the last block so the shear point in not lined up with the block mortar joint. If sounds like you may be using chimmney block which is more than reg 8" block. The chimmey block has a perfect 8by8 void to pour regular concrete. If hand mix don't be afraid to throw in any broken up stone or brick to fill. I personally would not worry about pouring the inside. wow its a 24" peir thats holding a DECK. the peir you want to build will hold a house on it possibly depends on coloum/ peir spacing.. A deck is real light. Think how long a two or three story chimmney stays up on down pressure and the building is the shear factor. Hope I helped.