Replies

1. 
   andybuildz | Jul 20, 2003 04:24pm | #1

   just to answer #3 etc

               Definatly 2x12 !!!!

   Its actually cheaper and easier and by all means stronger. Use long bolts made to hold forms together that stay in the footing when the job is done.

    Be sure to used some burnt motor oil on any forms so that they pull away from the concrete.

    You'll probably find uses for the 2x12's somewhere down the line as well.

   As far as alternatives to forms/footings, why not just do a trench footing flaring the bottom out and then up to grade and go from there? No forms necessary.

   andy

    

    

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2. 
   alias | Jul 20, 2003 04:58pm | #2

   theoretorically the slab and stem walls should be of separate components because if the slab acts in a certain way . and the wall acts in another. and any force that put to the slab will telegraph right through the wall. the host of movements that are in a horizontal slab are much diffrent than a stem wall's downward force . and when the footings are separate of the walls that is separate of the slab when broken up these all work together and separately if you understand my drift. when reactions are broken up they reduce the compound effects. that can sometimes double when things are together.

   now the disclaimer i'm a carpenter with a couple of generations of advice at my disposal. i've read alot of books educated myself, and have a fair amount of practical knowledge accumulated. there are alot more engineer's here who are probably a hell of more educated than i.

   a personal epilogue... go for it , alot depends on the soil mechanics and if the ground is relativly undisturbed or well tamped you could be all right... my 2¢ worth bear

1. 
   brownbagg | Jul 20, 2003 05:26pm | #3

   if your stemwall is only 17 inches tall, yes you can do it, we do it daily up to five feet. pour the footing first, dry, as dry as you can about 3 inch slump. then pour stem wall in two lifts with about 30 minute wait between lifts ( if it take 30 minute to go from one end to other, you can start second lift from other end) keep the vibration on stem wall to minimum ( I would not vibrate stem wall, it runs out bottom.) You pour just like if you was slipforming

2. 
   amaruoka | Jul 21, 2003 06:15am | #4

   The soil is very well compacted.  Infact, we have to use a roto-hammer to bust it up.  Besides, these footings are really only holding up one story (entire new second story is carried on new footings, foundations, entire first story is carried by old footings).  The city engineer is interpreting the plans as a two story addition and therefore wants footings that can hold two stories.   This house isn't going anywhere...

3. 
   RalphWicklund | Jul 21, 2003 06:33am | #5

   I can describe the forming process we just used to do a mono footing and stem wall that almost mirrors yours, except we didn't have to pour under the structure or lengthwise against another wall.

   We used ½" plywood for the forms. Because we had to rip up an old footing and a lot of monster tree roots we had to form the footing as well as the stem. The footing was easy. Butt the rips of the plywood end to end and drive 2x4 stakes on the outside about 30" o.c., taking care to have the top of the stakes flush with the top of the plywood form and the form dead level. With the top of the footing accurately defined, the height of the stem wall is then measured and the plywood ripped to size.

   When pouring, you want to make sure the concrete placed in the stem wall form doesn't run out over the top of the footing form. To prevent that I used a 2x6 on the flat and attached the stem wall plywood to the edge of the board, forming an "L" shape, which I then placed on top of the footing form. One long deck screw through the 2x6 into the top of each of the footings 2x4 stakes held the stem wall form upright and positioned cantilevered over the interior of the footing form 4". Repeat for the other side of the form. Add 2x's on the inside and outside corners to tie them together. With a 16" wide footing this produces an 8" wide stem wall. The top of the footing form is now leak-proof and you can pour the whole thing in one lift after you finish the stem portion.

   At the top of the stem form I used a length of 5/4x3, also on the flat, to stiffen the top edge of the plywood. I then cut 5/4 spacers to length and screwed them down across the top of the forms about 4' o.c., holding them apart at the planned 8". A little earth backfill was placed to the outside of the footing forms and no other bracing was necessary. If your locale requires, don't forget to add the footing rebar before you put the upper form on the lower. We also had to have one #5 in the stem portion so I just ran some tie wire through the forms to cradle the bar during the pour. Also embedded threaded rod at key points for the structures tie down system. Concrete was poured at a 4" slump and rodded into place. Since you are pumping and don't have much space I would suggest a 5" slump or whatever minimum the pumper will allow. Vibration is optional.

   Most areas will not allow wood forms to be left in the ground.

1. 
   BungalowJeff | Jul 21, 2003 07:21am | #6

   Ralph has given you good avice, but I would say check for an 8" slump mix from your concrete plant. The pumper will love it and it will flow around the rebar with barely any vibration. Also, in almost any concrete structure, the fewer cold joints the better, so go monolithic....that's not a mistake, it's rustic