New Patio Concrete Slab - Slope Question
New Patio Concrete Slab - Slope Question
(OP)
Hello all,
I am going to help my brother pour a new 11x33 ft concrete patio. I am curious about slopes for drainage - what % is ideal? 1%?
Thanks
I am going to help my brother pour a new 11x33 ft concrete patio. I am curious about slopes for drainage - what % is ideal? 1%?
Thanks





RE: New Patio Concrete Slab - Slope Question
I would strive for 1%. The reson is that it will be very difficult to achieve a uniform grade with anything under that slope. This way even if it flattens to .7% or .5%, it will still run. If you start at a flatter grade, it is inevitable that the little "bird baths" will develop and be a nuisance. I just helped my father-in-law build a new patio slab, and 1% was the grade we used.
Also, try to string the perimeters as much as possible for your finishing reference during the pour. Using this to set the form height is invaluable!
KRS Services
www.krs-services.com
RE: New Patio Concrete Slab - Slope Question
Should I cure this thing? THere won't be any heavy loads on it. Maybe I should just occassionally spray it down with water the first few days it cures?
RE: New Patio Concrete Slab - Slope Question
RE: New Patio Concrete Slab - Slope Question
It is commonly insufficient, due to settlement.
More than 1% is desirable for a patio. 2% is not too much, if the slope is available. Most people use a slope of 6" in 10' away from a building, and then switch to a lesser slope.
After 37 years in the same house, I wish I had more slope away from the house. (Too late now to change)
RE: New Patio Concrete Slab - Slope Question
RE: New Patio Concrete Slab - Slope Question
Yes, you definitely want to cure the slab. After finishing the slab, wet cure it for 3-7 days by covering it with a 6 mil. clear poly. I would also spray water over the poly. to help keep the temp. down during the summer heat. The clear poly can sometimes leave "fold marks" on the concrete, which should wear off in a few weeks/months. After the 3-7 days use a high solids, non-yellowing cure & seal compound. Firms like Sonoborn, R.W. Meadows, and Master Builders all have good ones sold in gallon containers. Follow their directions!
RE: New Patio Concrete Slab - Slope Question
RE: New Patio Concrete Slab - Slope Question
The wire reinforcement does not eliminate cracks – it simply holds them together. (probem is it usualy is on the bottom)
The fiber will help as micro cracks begin to appear due to shrinkage as water evaporates form the concrete (plastic shrinkage), the cracks intersect with the fibers which block their growth and provide higher tensile strength capacity at this crucial time.
RE: New Patio Concrete Slab - Slope Question
I know subgrade preparation is very important. Could we just tamp the heck out of it with shovels or should we actually rent push-compactor/vibrator?
RE: New Patio Concrete Slab - Slope Question
RE: New Patio Concrete Slab - Slope Question
RE: New Patio Concrete Slab - Slope Question
We though about doing it in 2 pours on different days, but then we'd get hit for a minimum load charge 2 times, so we are going to do it all in one pour.
Definitely will joint the thing, and will probably rent a compactor aswell.
RE: New Patio Concrete Slab - Slope Question
RE: New Patio Concrete Slab - Slope Question
Good advice, mostly. I've got to disagree with your statement that "if you are worried about cracking or strength, more cement in the mix will also help". Actually, more cement in the mix typically requires more water to hydrate it and leads to increased shrinkage cracking. I would recommend using the lowest water/cement ratio along with the lowest strength concrete that will do the job. ACI 318 Table 4.2.2 gives maximum w/c ratio and minimum strength requirements for various exposure conditions.
RE: New Patio Concrete Slab - Slope Question
RE: New Patio Concrete Slab - Slope Question
RE: New Patio Concrete Slab - Slope Question