I am building a three story concrete house and am trying to
achieve a smooth exterior finish when the forms are stripped
with little to no extra work.There are no hi-tech forms
available to rent in my area with the composite face required to
achieve this especially since each lift is 10 feet.I was thinking
of buying 3/4 ply with the smooth finished face and using that
for the forms and then reusing them for the subfloors.
Anyone had any experience or knowledge of this being done? All
comments as to the advisability or possibility of this would be
appreciated
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Ford Motor Company slashes prices for some F-150 Lightning models to stimulate demand for electric vehicles (EVs).
Featured Video
Builder’s Advocate: An Interview With ViewrailHighlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
Special order some 10 ft 3/4" t&g ply from your lumberyard, give it several coats of paint. Then after using it for forms, use it for the subfloor.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
You want a truly smooth face get 3/4" MDO GIF (Medium Density Overlay - Good One Face) It's exterior rated ply used mostly for concrete forms and highway signs.
Let's not confuse the issue with facts!
If you use 3/4" plyform (the plastic-coated plywood you mentioned), it may not be rated as subflooring, and it definitely won't have a tongue and groove. You'll end up using a second layer of plywood underlayment to stiffen the floor system. You may also want to check with the building inspector to see if he'll allow it's use as subflooring after it's been drilled full of holes for form ties, etc., and subjected to several cycles holding up wet concrete.
Also keep in mind that you're going to pay a large premium for 10' sheets- is there a way to incorporate some jointing into the exterior wall layout so that you can use 8' sheets? You're already going to have some jointing due to the split pours, so can you add one more line to the reveal pattern?
I've done several concrete-framed projects with architectural exposed concrete elements- if you'd like to email me some drawings, I'd be happy to look at them for you.
Bob
You are going to have vertical rows, full height, of pock marks from the snap-ties.
You are going to have a 4x8 or 4x10 grid of seams.
If you want an even surface, plan on more than a little extrior work.
I would just spray Xypex on it after filling the snap-tie holes.
Or stucco.
Off topic, but I've got to ask-
what do you mean "spray xypex on it", I've used xypex before as a waterproofing concrete additive, but never as a spray on coating- is this a slurry of stucco or cement with xypex added?
zak
Zak,
Xypex comes in several formulations, one can be brushed, rolled, or sprayed as an externally applied waterproffin.
It does its' microcrystallization thing to the outer surface of the 'crete.SamT
Greetings, and welcome to BT, first off.
I am building a three story concrete house and am trying to
achieve a smooth exterior finish when the forms are stripped
with little to no extra work
Now, let me offer a slightly different idea. You could go to your concrete man as say "give me the best finish you can," then when the forms are stripped, come back with a parged portland finish (or a 'proper' stucco in a very smooth final finish).
I say that, because that approach is likely to be easier (read either faster or cheaper) than going for a super-smooth from-the-forms finish.
Let me add, that a couple of years ago I was stuck with an owner who wanted a finished appearace straight from the forms. This was a less than good experience for all hands. Concrete sub hated it as the form liners were only good for one "shot." He also hated the form liners as he had to use a plastic tie on the forms, and they were flat awful (either would not snub up, or busted off, or would not snap clean once out of the forms). In addition, all the work with the "structural mix" concrete honeycombed on any defect, any liquid, anything at all on the form liners. So, the concrete finishers wound up running a high-portland slurry to "finish" all the concrete anyway.
For the additional labor hours, the additional form liner cost, and the delays, all that cost, they could have used ordinary forms & finishing, and had cultured stone on and been finished early--but that was a "snakebit" job from stem to stern, not at all like yours, of course.
Since you sound like you are using the concrete as an exposed finished material, that poses a couple of question in my mind. Like, how are you insulatign the walls? And, how are the doors and windows going to be trimed out?
Oh, and have you thought about using ICF (Insulated Concrete Forms)?
Just the sort of info i'm looking for Appreciate it.
I looked at icf's very closely and a piece of info
came my way that stopped me cold.A icf house was
built locally without a/c as is normal in this part
of the world.
With a hot summer about 100f the place became virtually
uninhabitable.A friend of the owner building with icf's
just about the same time quickly added a/c to her plans.
I ended up corresponding with the Livermore Lab on this
and the story is that the thermal discharge time of an
icf build can be so long that it will not cool down.
It picks up the heat in the day and the night is not long
or cool enough to shed it so it keeps racheting up and up.
So better put in a damn good a/c and be prepared to pay
to run it.So insulation one side for me(furred and drywalled)
so it can shed that heat from the uninsulated side at night.
Where in the world can you possibly be building that it gets to be 100F in the summer, and its not SOP to install air conditioning in a new house?????
Bob
Vancouver island.That was a unsually hot summer but with global
warming who knows maybe it will become the norm and maybe a/c
will become SOP.It isn't at the moment.
Since you're living on the Island ( I'm on the Mainland )you can go to an industrial area that is putting up warehouses and factories. Look at the concrete walls that are poured on the floor and then stood up with a crane. Same system will work for residential. There was a Fine Homebuilding article some years back where a man in Colorado did the same but he laid rock on the ground first before the concrete pour. When they were stood, he had rock walls on the exterior.
Don't blame that on ICF's. The house likely had windows that got excessive solar gain--south or west-facing windows with no overhangs--with no provision for ventilation. It essentially became a hotbox. Blame the design, not the materials.
that the thermal discharge time of an icf build can be so long that it will not cool down
Hmm, well, let's see, we have dense foam, masonry, then more foam--yeah, that's the kind of thermal mass that could have a problematic "thermal lag." Of course, there's a lot of variables involved, too (like percentages of door & window openings, ventilation, etc.)--sometimes more is less.
Occupational hazard of my occupation not being around (sorry Bubba)
Go with ICF, Insulated concrete forms, stucco outside, save a lot of headache , probably cheaper than forming plywood you have to buy, easy to assemble and get insulation value too. ARAXX has planbook and help you with it, a few have done thislocaly , everything but roof trusses.
IF IT WAS EASY, EVERYONE COULD DO IT !
Or, go this route...precast will give you a factory finish on the interior and exterior, with insulation in the middle.
http://www.dow.com/styrofoam/na/concreteliving/