is this raised rear porch possible???
Hello,
I’m still building my place and of course we noticed a design problem too late. The house is bascially done and the rear covered porch of my 2 story house, of 12 x 14 was, supposed to step down, then just basically be a cement pad. After figuring out exactly where the steps will end up, we are deciding to have the porch go right out from the patio doors to the end of the porch (about 14′), then have stairs going down from there. This way our patio set will be able to fit under the covered porch as intended. There were 3 footings poured during the foundation stage for the steps off the patio doors (there is 3 patio doors w/ the center operating), however since the steps will now be after the porch, these won’t be used for the steps now. The only other footings I have is for the 2 posts on either corner of the covered porch. OK, so there’s the background, and here’s the question. One more thing, the house was excavated in mid October of last year and has about 6″ of crushed stone that was tamped down.
Now that we want to change the porch and have the pad directly off the patio doors w/ the steps at the end of the cement pad (about 14′ per above), here’s what were thinking of doing:
– dig a 4 – 6″ deep trench around the perimeter of the porch
– place rebar in the footings on either each of the corner posts and have longer rebar coming from the footings that were originally intended for the stairs
– pour cement in this trench and ensure the rebar is properly secured in the trenches
– build a retaining wall out of the brick that matches my house (full brick 2 story) all the way around the perimeter of the house
– fill the inside of this retaining wall with broken bricks, gravel, etc. then form the cement pad
– pour a 4″ cement pad
– next, pour the stairs
– add railings where necessary
So – will this work, or will there be any issues in the future of the bricks moving, etc. or will this idea be sufficient where I shouldn’t be at any greater risk of the cement pad cracking / failing prematurely? Also, is there anything else I should do or any other recommendations? Thanks!
Replies
Sorry, but without a drawing, I am a bit lost in all that text verbiage. Do you have a plan and elevation drawing you could scan and attach or a photo to help orient?
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
I believe he says he's going to dig a 4 to 6 inch deep footing for a retaining wall. But it's gonna have rebar!
He must live in southern Mexico or someplace like that. When I lived in S. California, we still needed 12" deep footings.
What confuses me is that it sounds like this new revised slab will be higher in elevation than he'd planned, but he is digging down lower...???
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Rereading his story three times, I believe he wants to have a raised patio under his existing covered porch.
But then he gets pulled down by the construction details with all of this concrete. I note his porch roof already is in place and properly supported by posts on footings (depth unknown, but assuming below frost level, if any).
Right off, I think he may be better off looking at retaining wall products, but he wants the walls made out of the same brick as on the house.
If that's the case, we need to focus on how he constructs these footings. He does say his new rebar will interact with the existing post footings, so I'm assuming the depth of his proposed footings will be good, but his comment of 4 to 6" confuses me.
But once that is straightened out, his desire to pour steps may need to be tempered. I'm thinking his brick should be involved.
Wow--I'm confused. I too have read the original post several times. Not sure how he intends to tie into longer rebar that's coming out of the original footings for the steps if the footings have already been poured (or haven't they?) Don't understand the retaining wall thing at all--all around the house--retaining what? The house? Anyway, brick doesn't seem to be a good material for that. Maybe he does live in New Mexico or Florida. Maybe he'll respond.
I'm also not seeing how a patio set that fit on a patio that was designed to be three steps down from the house (making the enclosed space taller, no?) will now fit better when the patio is extended from the house with its floor same height as floor of house (higher than as designed) (enclosing a shorter space) out 14 feet. Or is he storing the patio furniture under the patio floor? Yeah, drawings, photos, hands waving in air would help!
Edited 6/7/2008 12:35 pm ET by Danno
What confuses me is that it sounds like this new revised slab will be higher in elevation than he'd planned, but he is digging down lower...???
I think that is exactly the case.
Plan one was to come out the slider onto a step or two, down to a "patio slab" (thin 3-4" basement-style pour, bounded by the corner footings of the deck/balcony above and the house (ignore the reference to step footing/foundation) as is.
What I think has happened is that the Design Committee has seen this in situ and wants the patio, but up even with the threshold (more or less) of the slider, and still under the deck above. As a guess, 12' out from the house, it slopes more than a foot or so lower than up by the house.
And, since that is the case, the thought has come in on how to dress that exposed concrete (which might be exposed 1.5-2' tapering back to only 8-12" exposed at the house).
I'm guessing that this next idea was to make a foundation beam for the patio, which then gave us the confusing reference to "what do I fill the void with?" over which to apply a few inches of "patio" concrete.
Now, if that is the case, we really need photos, as I'll bet the existing brrick ledge is near by, but probably not in the right elevation to wrap the patio elevation--but naggingly close.
I don't think OP was thinking about pouring this monolithically, the way many of the rest of us would. I'm thinking that I'd like to know where on the house dimesion the 14' width sits, as if this is a long way out of the ground 12' away from the house, the sides will want design attention, so that the patio is not a "wall" to the rest of yard.
Also, if this thing is very far out of the ground, local code (and good sense) may require railings, which could make for a claustrophobic patio under the deck above.Occupational hazard of my occupation not being around (sorry Bubba)
Isn't this fun?! My first concept in mind was that the roof over this had not yet been built but only planned and intended.I read the whole durn thread thru again and I think you are right. A lot depends on the existing grade and house footings as well as climate zone. I'd alslo want to know what pitch the roof and where that beam ends up. If it is as you describe his intent I would probably plan to build the slab one step down from the interior floor level and form the slab around the posts. Fill the interior with same compacted crushed stone as the rest of it all. I would form this so that the perimeter beam and rebar is continuous just behind the posts.Heck - I'll go one better here - I'd spend an hour or two and make some temporary leaning posts that seat outside the slab zone to hold the roof, remove the existing posts for the time being, and pour the slab, then reset the posts on it.Keeping one step down from threshold is how we do here to avoid floods and ice blocking the door out. For the OP, it would mean he devotes no floorplan space to steps so he has room for furniture, and saves on how much fill he needs. It also helps with the tunnel vision effect you addressed by adding about 8" to the open elevation.
My interpretation of the layout is that the outside edge of the slab will be 14' from the house doors and the patio is only 12' wide. It did strike me as an odd size.Every few months we get one of these ponderables that leaves us hanging with nary a re-visit from the OP that turns into a good discussion regardless...;)
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Every few months we get one of these ponderables that leaves us hanging with nary a re-visit from the OP that turns into a good discussion regardless...
Yeah, no lie.
I'm still not sure, even after having read the OP eleventy times, whether that second floor balocny/deck has a roof or not--it kind of reads boths ways, iffin I squint at it a bit. It does not sound like anything is on the deck footings, maybe, kinda.
And I'm also in that "I probably don't want to hear that the 14' x 12' deck is held up only on two 4x4 posts" sort of thinking, too (doubly so if there is a roof up there, too).
If this thing is tall enough to start thinking about brick facings, my thought is why not just use wood again, mirroring the deck above. Then, steps could come down to whatever hardscaping suits. This especially so with a roof over head, so that it would look integrated to the house, and not some sort of room cantilevered out of the second floor (which happens too often).Occupational hazard of my occupation not being around (sorry Bubba)
Sorry guys, my computer was down and I just got it back. I'll post pics later,but to hopefully provide some clarity:
- I live right by Detroit, MI
- the rear covered porch is already completed
- the footing for the 2 outside posts and the area where the stairs were originally supposed to go are 44" deep
- basically I'm just tring to have a cement pad raised up so it goes straight out from the patio
- the entire 12 x 14 covered porch area will be one big slab
- the stairs going down will be off one of the sides, with the other two sides contaning railings
- the two posts helping support the covered porch will be "inside" the cement pad w/ the retaining wall being flush with the outside edges of the posts
- the posts are 6" x 6" P/T w/ Owens Corning cultured stone on top of them
- the roof pitch is 8 x 12
Hopefully this helps bring a little clarity. I'll post a pic a little later.
Thanks again for your help (and patience).
Gosh darn it all - I am still confused nowThe covered porch is finished, but I thought the floor in under the porch roof is what you were talking about."to have a cement pad raised up so it goes straight out from the patio"Where in the world is the patio? I thought it was outside the porch.cultured stone on top of the posts? you mean facing them?And is the 12' side perendicular to the house or parallell to it? Is the roof a gabled dormer style?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Where in the world is the patio? I thought it was outside the porch
No, directly under the upstairs porch. It's an upper level deck with roof, which is on whatever designed columns & footings as are needed. So, right now, OP has just dirt out the lower level slider.
If I'm reading this right, plan was to stay on grade for the patio slab, but the Design Committee, she has over-ruled that.
If I'm still reading this right, if you stand in the lower-level slider and look up, you see the bottom of the 14' w x 12' upstairs porch/deck. Look left 7 right and there are columns holding up said deck. Look down and it's two steps, call it 16", down to grade below.
The program I think OP probably needs is to get in and do the subgrade prep. Then set up the formwork for the level patio, using carton forms to fill much of the void. Hmm, probaly need to put some isolation membrane against the house and porch footings, too. Set the bar in place, and get the concrete placed.
Now, the final dimensions of the patio will need a design decision on how any cutured ston goes on the extant columns, which will be defined by what, if any, surrounds go over the structural members already in place.
That more clear?Occupational hazard of my occupation not being around (sorry Bubba)
I give up'till I see pictures or drawings
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Here are the plans. The back is exactly the same except for the grade entrance off the back. As you can see the original plans called for stairs coming off the patio door and now I want to make it straight from the patio door until the end of the posts, then have stairs off of that. This will allow me to put a patio table under the entire covered porch area. One more thing, the porch is 15' wide x 12 ' deep. Sorry, I mixed up my measurements again.
Thanks again for your help.
OK, I am going to mull this over for a while in the back of my mind today. I have the picture and re-read the thread again.Part of the misunderstanding is that you seem to have used the words porch and patio interchangeably, making me think you had both to contend with.First thoughts are that for your climate, you need the footing for this to be placed that same 44" below grade for frost protection and that any infill should be compacted, not just misc junk and debris. To ignore proper footing depth and compaction of infill means the raised slab will be destrioying itself within a couple of years, which is a shame for such an otherwise nice house.Normally I would have answered to just re-grade, but that would be a serious complication given the bump-out bay window and the excavated egress from basement level, so you probably need the raised surround. Frankly, I am surprised the retaining wall has no rail at the top of it to prevent falls.seems to me from a design POV, you are creating a lot of complicated work just to be able to place a patio table set.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
What's a "carton form", Cap'n? (said with that kid's accent on the What's.......)
What's a "carton form"
It's a corrugated paper box form used to make a stable fill for the middles of large monlithic concrete pours. SureVoid, Voidform are a couple of brand names. The boxes are waxed so as to not soak up water from the 'crete, and are laminated of enough layers to support the load until the 'crete cures to self-support.
Nearly ideal for OP's situation, where the final elevation is significantly above undisturbed grade and adding and compacting fill to then trench out turndown beams is impractical.Occupational hazard of my occupation not being around (sorry Bubba)
Thanks. Never seen one. Lot's of concrete front porches here, I always see them filled with rubble.....I guess it saves the cost of removal, and extra fill's probably cheap. Wonder if, long term, using the void forms give a better product?
Wonder if, long term, using the void forms give a better product?
Over random construction debris fill? Several orders of magnitude.
You just can't compact a pile of old bricks, rocks, concrete washout and the like to any known value. Put 4-5' of concrete over an unknown base, and when that base fails, the concret has to do all the work. And, typically, it won't, it hasn't been engineered to do so.
For creating an elevation well above existing grade, carton form has few equals. Way cheaper (especially with diesel prices) than trucking in clean, compactable fill. Nice part is that bar and chairs and VB (if needed) will set nicely on the carton forms, unlike a dicey pile of fill.
But, I'm biased in this (among other things). Jaded & cynical, too by common affirmation.Occupational hazard of my occupation not being around (sorry Bubba)
Pretty much what I thought. It's a shame so many contractors just keep hogging it in there....I suspect more than a few of our fellow BTers are members of the jaded and cynical club.
well this has been an interesting foray into the world of carton forming starting at google
one site was a test report that a groupd conducted. Have you seen it? the pdf
Have you seen it?
Have now, and it was worth the 15 minutes to get it downloaed (and saved locally, too).
I'll have to remember to spec masonite/hardboard over the top; that's such a good idea.Occupational hazard of my occupation not being around (sorry Bubba)
so is the assumption correct that the expansive soils, once expanded won't contract and leave a void? I don't mess with foundations and soil condition details much.
glad it was worth the wait.
so is the assumption correct that the expansive soils, once expanded won't contract and leave a void?
Ah, now there's a question to make the structural engineers go all quiet-like.
The first presumption, generally, is that "properly compacted" means "expansion controlled." Meaning, as I understand engineerspeak, while not being one, to say "Contractor must do a good job."
So, as I understand it, engineer makes a bet, of sorts, that soil preperation will help control the expansion, and a certain amount of over-engineering the slab means it can span any subsquent soil changes underneath it.
Mind you, I'm more used to suggesting things in sectional drawings with notes on them like "Conc. slab on carton forms over compacted subgrade per Structural" too. Have to be just smart enough to express intent, so the engineer can then sweat numbers to the task.Occupational hazard of my occupation not being around (sorry Bubba)
OK, now I need help for sure. I think we're going to go ahead with the raised porch. I really value your guys thoughts on the form. I know people around here don't use these, so do you put these down after the fill is put into the void, or put into it first, then put the fill on top? I apologize for my ignorance on this topic, but I want to make sure I get it right since I doubt anyone around here knows what to do with these products.
Another thought I had which I know some guys do around here (and I would love to hear your guys input on this) would be as follows. The footing will be approx. 8 - 10" wide, and the brick retaining wall out only take up a portion of that footing. On the other areas, I could frame a box and some 2 by rafters to hold up a galvanized corrugated steel sheeting. It's quite thick and was actually used on my front porch. Apparently all the custom builders in the area use this to support the porch pads when there is a cellar or something underneath them. In this case, I would use it to stabilize the cement pad. I figure if the framing is attached to the footings and the corrugated steel is on top of the framing, then the pad should be relatively stable, no?
Again, any thoughts, etc. on this alternative are welcome. I'm just suggesting it b/c people around here are familiar with this technique vs. the void forms, etc.
Thanks and I'll promise to include pics as we finish it up!
so do you put these down after the fill is put into the void, or put into it first, then put the fill on top?
Process is compact the area, then trench out for the turndown (I believe you mentioned a 44" requirement). Poly sheeting then goes in. Then, while the exterior formwork is placed, the carton forms go in side of that formwork, up to the bottom elevation of the slab. The cartons are decked over (with hardboard, I now know to specify). After that the rebar is set in place and properly positioned. Concrete is then placed and finished to the top of the exterior forms.
The carton forms mean noy having to try and get compacted fill in under the existing structure especially to the depth required. Also with the benefit of not making a compacted pad to then have to excavate out deep trenches in the expensively-placed fill.
Now, using corrugated sheet metal to span than carry a curing concrete slab is possible, but also complicated, too. You would likely need a foundation beam in place (four sides, like as not) to provide a spot to bear the decking upon. How much bearing varies by the type of decking used (gauge and shape and span and welded or loose all factors). Now you are into needing actual real-live engineering again. Possible, but the details need a lot of attention before construction (like the edge finish of the slap parallel to the sheets; how the rebar used ties in to the slab at the top and bottom of the sheets; add in the doweling needed at the house side of this while also having a isolation/seperation memberane in place).Occupational hazard of my occupation not being around (sorry Bubba)
Grandchat.
You need to give us picts or more info.
Also fill out your profile.
click on your name and it links you to your profile.
Then we could see you are in southern NM and we could confirm that you dont need footings down 36" or 42" below grade for frost protection. (Frost protection is anywhere from 12" to ????- I guess they dont have frost protection in the Arctic since they probably just build on the permafrost!?!?!