Concrete Pouring Basics for Deck Stairs?
dirtbag
| Posted in Construction Techniques on
Am within a couple days of pouring a concrete “footer” strip for my home deck stairs (6 stair stringers) to rest on. My trusty Home Depot book (yeah, I’m one of those weekend do it yourselfers) recommended a 30″ wide and 6″ deep affair (most below grade), but says nothing of rebar or mesh in the pour for strenth.
Thoughts? If it’s anything other than, “just fill with concrete, and to heck with reinforcement.” what is the best way to go about it?
Replies
What's your climate like? If you have frost, perhaps more important than reinforcement is drainage. Remove all loose, non-mineral soil. Put down a layer of gravel for drainage, and compact it. Then pour you concrete.
Al Mollitor, Sharon MA
It freezes in Yorktown (south east corner of Virginia) in the winter, but not normally big time. Code requires deck footers for posts/beams be only 12" deep. We had an abnormally cold december/january last winter in which the pond in our neighborhood froze enough that one brave (an likely very foolish) kid ice skated on a small part of it.
Will be sure to use gravel... thanks. But, still suspect rebar and/or concrete mesh is not a bad idea. Not sure if it's a factor, but the stair pad will support 20+ stringers, 16 O.C. Is reinforcement overkill for the load?
Bob -
I'm one of those anal type guys that never places concrete without some sort of reinforcement. Min. would be either 6x6/10ga welded wire mesh (which mainly only serves as crack control) or #3 (3/8") rebar at no more than 16", preferable 12" oc. Rebar is easier to maintain in position than mesh but takes more time to place, chair properly and tie to get a good job with it.
Without seeing your design it's not possible to judge whether the concrete pad would be strong enough without any reinforcing ... I suspect it would be ... but take the time to do it right and put in some anyway. In ten year's time, you'll thank yourself for it.
...........
Dennis in Bellevue WA
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Hi Bob.
Yes, do use gravel, and do compact it. Do use rebar. If it were me, I'd use 1/2 inch rebar ( no. 4) instead of the 3/8 dia. stuff. You mentioned your pad was to be 30 inches wide and 6 inches deep, but did not mention the length. Based on the info you gave, I'd run 3 pieces the length of the pad...I'd place the first piece 3 inches from the inside form, then the next piec 12inch OC from that one and the next piece 12inch OC from the latter piece....which would give you a 3inch space on each side of the inside form. After placing these horizontal pieces, I'd place rebar perpendicular to these so as to form a grid pattern. I'd start about 6 inches from one end of the form and place all rebar 12in OC from there. Tie all the rebar together. You can place a tie at every other connection point and this should be plenty strong.
Put the rebar mat on top of concrete chairs ( your concrete supplier carries these...don't use bricks except for least resort if unable to find chairs. You want the bottom of the 3 pieces of rebar you laid first to be sitting on these chairs, and to be raised 2-3 inches off the ground. Having the rebar positioned a little closer to the ground, rather than placed smack dab in the middle of the pour is actually a little stronger that way.
I'm curious...in one post you mentioned this pad would hold 6 stringers...in another post you mentioned 20 stringers...though I'm assuming you meant 20 risers?
Anyway...for what its worth, a stair that is 30 inches wide ( though I'm not sure this is what you are building) really only needs 3 carriages (stringers). For added strength, keep the 2 outside stringers closed ( use cleats bolted to the stringer for your treads) and just open ( cut-out) the middle stringer. Three stringers are plenty strong. As for 20 treads....if this is the case, you perhaps should plan on building a platform part way up the stair case....normally a platform is required if there are more than 13 risers. If this is the case...20 risers...I'd think along the lines of making the 10th riser into a platform and then start another 10 risers from the platform. Just my 2 cents.
LOL on your stair/deck project.
Davo
Thanks, for the details on rebar, where to place 'em, and the benefits of concrete chairs. An excellent run down for this novice. I'm on my way to Lowe's for the rebar, ties and chairs. Looks to be a busy day.
As for the confusion on stringers vs risers, it will be 20+ of the former and 6 of the latter. Will use 1" x 6" ipe boards.
I poured 2 of the 3 sections yesterday. Longest lengths of rebar Lowe's had were 4'. That, combined with the concrete or rod chairs that gave 6" OC convinced me to go with 3/8 bars. Since the chairs held 2 bars, I ran two courses of bars at 4" and 10" from the sides. Then a big thunderstorm blew through here about 5 hours after I finished. Hope everything survived!
Thanks again, Davo.