You must be on a severely sloped lot if you are going to have large windows in your basement walls.
I don’t see any thing different regarding water management. A nine foot wall is a nine foot wall whether it is 8 feet of concrete and 1 foot of knee wall or just 9 feet of concrete.
Why does the architect want the knee wall. A header would be required above windows/doors in any case so whether its a part of a wood kneewall or a reinforced part of a nine foot pour is immaterial.
I would agree that a poured wall, without a kneewall, would be inherently stronger construction and one less step in fabrication. The additional thickness requirement for an additinal foot of concrete would necessarily increase the material (concrete) cost. However, that cost would still be incurred in material and labor for the kneewall.
My house, if it had a basement, would have about 190 lf of basement wall. Using that measurement would require an additional 15.3 yards of concrete, taking in to account the 2 inch increase of wall thickness and foot in height above 8 feet. My additional concrete cost would be just over $1100. And there would be a little more in there for the forming. Your milage would vary?
I like the 9 foot pour.
If Mike Smith weighs in on this thread he might be persuaded to repost the pictures of a basement wall he had poured. He uses a company that employs reusable forms. There should be some companys in your area that specialize and use reusable concrete forms along with conventional forming methods to accomodate your height and penitration needs.
Edited 12/28/2003 11:23:22 PM ET by Ralph Wicklund
Replies
Ralph, don't forget that headers can be done in the rim joist space.
That last foot of wall would cost me a much higher cost proportionately than each foot of an eight foot wall because most of the forms are eight footers. That might be the architects reason. he is there to keep costs down. I can well imagine that the exterior elevation will not look as pretty with the crete sitting higher to look at when you walk up to the house too.
The best reason for the higher wall would be if this is in a seismic zone and shear walls are necessary.
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Do the 9' pour.
For what it's worth, 10" thick pours are the norm here in CT.
Check if forming outfit has 10' form material available (assuming Strip-EZ system). 2'x10' form ply is a special order normally so this will increase the forming cost. But if they use single or double waler system (much stronger than flimsy Strip-EZ) then you can go with lay-down forms and 9' pour ht is no big deal - should cost very little extra for forming time, just extra steel and concrete. The extra thickness represents only a material cost increase, not a forming cost increase. Remember the forms don't have to be especially strengthened for the thicker section, pressure increases according to depth, not thickness.
I can see the materials and labour for the pony wall pretty much eating up the extra costs of the 9' pour. If architectural considerations allow it, go for the 9' pour. Better yet, go for a 10' basement. Pretty common round here lately- makes an awesome shop or games room and definitely helps resale.
Wally
Lignum est bonum.
I'am with Mongo, and whoever else may go with a nine foot wall. Your one foot Knee wall, well think of it as a hinge, if your around earthquake prone areas. One last note; make certain that your ingress/egress window wells meet your building codes. . Good luck, and do not forget to have some fun on your project. Jim J
Bigger is better, and thicker is stronger.....
I'd opt for the 9ft concrete... if you can afford it.
Davo
You did not say what your exterior finish is going to consist of. Our code requires the grade be no closer than 8" from the top of the foundation wall. That is the concrete, not the knee wall. We get a lot of brick to grade finishes here also. That means an 8" brick drop in the foundation wall. The height, and lineal feet of brick drop do add significantly to the forming cost. Or, if you don't mind seeing 8" of foundation showing above grade, you have plenty of room on a 10" wall to set the brick or ant type finish you want.
Dave
I think it's a matter of where finish grade will be against the foundation walls. I don't like to leave a lot of foundation showing, so we use knee walls on top of stepped foundations often when we build into a slope - let's you side those walls on the outside and drywall the inside - keeps the exposed concrete wall(s) to a minimum.
I'd most likely go for the 9' wall. But I'd ask concrete guys in your area first. A lot depends on the kind of forms they have.
I asked my concrete guy how much the difference was between 8' and 9' walls when I built my spec house. He said it was only $600. He said his forms were 9' anyway, and they just had to snap a line inside the forms and pour to it. So the only difference was the added concrete and a bit of labor.
But other concrete guys have other kinds of forms - This seems to be a real regional thing regarding what's "normal". So it would proabbly be worth asking around locally.
I agree that the higher pour would allow you to slope the ground away more than an 8' pour with a kneewall. (Without geting the house too far out of the ground) I wish I'd set my basement walls a bit higher and sloped the ground away more. It's a lot easier to add fill around the house to slope it more than to dig dirt away in a large area.
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Drugrep,
Would it be possible to lay two courses of 8" block on top of the wall. Or if you really wanted just 12", you could go 8 and 4. I don't think I've ever seen this done, but I can't see any problems, other than scheduling.
Jon Blakemore
I would build a pony wall before stacking cinder blocks on a poured wall if that is what was impied above.
However for me or my customers I would build the walls out of ICFs
but thats a whole other discussion
silverhammer,
Why? Let's say that your neighbor is a retired blockmason. He is willing to come out one afternoon and lay two courses of block for a reasonable fee. What would be the downside? Messy connection of concrete to block to plate? Dissimilar materials looking strange? Too much trouble for the benefit?
Jon Blakemore
retired neighbor who wants to work, let him at it, im all for hiring neighbors and friends if skilled and it is nice to have a friend neighbor havein imput in your home
scheduling can always be worked around
looks, looks can be good. say the poured wall is nearly below grade and you do the block with splitface, coud look really nice, I would prefer it to just a plain concret poured wall look
would be concerned with the "hinge" aspect and the bond between the block and the foundation and then the house to the block, all issues easily addressable
a lot depends on elevations, desired look, etc. The wood pony wall couuld be covered in the same materils as the house if high enough above grade
icfs arent always the best answer either because you have to cover for apperence and protection
Im not saying my way is right, just throwing out a thought or an opinion.
the key to it all is , what is the code, what is the desired look, what is the cost, what is the best long term , and what is the emotiinal benefit to the owners, all not necceassirly in that order.
hey anyone know why my post looks like that
Silverhammer,
I don't know what happened to your formatting. Maybe Luka or somebody will stop by and help you out.
I never thought about split-face. Now I'm thinking. That could really be useful if you could plan your grade to be a few inches below the conc./cmu joint. I don't know much about split face. Would there be trouble attaching the PT plate to it?
Jon Blakemore
I figured out what was wrong with that post format.
I would avoid making the joint below grade if possible. this might be like a cold seam and maybe allow water to weep in. maybe ok a litlte for a foundation but not for a daylight basement. unless you seal it well, really well. Here in Oregon if water has a path it will follow it or make it
Out here we call them split block. Cinder block that has a rough rock texture to it.They are flat across the top, bottom and sides. It still has the hollow cells that you could put your j-bolts in and fill with concrete. Then of course your sill seal and then your p.t. sill
Maybe to avoid the hinge effect you could put some long j-bots in the poured wall that go past the block into the new mudsill.Similar to having rebar poke up from a footing into a stack block wall. Or maybe some long simpson straps on the inside of the wall that would go up to the sill or joists
check your codes and local engineer and of course your blockmason of choice will know the rules and the how to
hey anyone know why my post looks like that
Somehow you clicked on the "Right-justify" button. That is those 6 little lines with the right ends aligned underneath the "Font" selector.
SamT
Edited 1/1/2004 8:34:25 PM ET by SamT
The 9' concrete is well worth the additional costs. Every forming system can be added to (15 yrs experience) I agree completely to use large windows (and window wells) to admit large amounts of light to reduce the perception of being in a basement (assuming a finish equal to upper levels) I also predict that in the near future; high quality finish of lower level spaces will be recognized in appraisals.
Edited 1/1/2004 8:28:36 PM ET by Rocks4sale