Why does a fresh concrete patio need to slope at all? Because water has to go somewhere, and a dead-flat slab beside your wall sends it the wrong way. The fall away from the house is a layout choice you lock in before the pour, not after.
Slope a concrete patio so water runs away from the house, never toward the foundation. QUIKRETE’s patio guidance is 1/8 inch of fall per foot of run. Other guidance, such as Building America, uses about 1/4 inch per foot, roughly 2 percent. The numbers differ, so check your local code before you set the forms.
Which Way Should a Patio Slope?
Always toward the yard, away from the house wall. The goal is to move rain off the surface and keep it clear of the foundation. QUIKRETE says “most concrete surfaces should have a slight slope,” especially near your house.
Concrete is nonporous, so water does not soak through it. The Building America Solution Center explains that water pools around the foundation when a hard surface does not drain away from the home. A steady fall sends that runoff out toward the lawn or a drainage area instead.
You decide the fall during layout, then size the slab once you know the shape and thickness. For the concrete itself, the concrete patio calculator estimates volume and bags from your dimensions. The slope is a separate layout step that lives in the forms, not in the mix.
Before you build forms, QUIKRETE suggests checking the slope of the existing ground where the patio will sit. You measure the drop across the area, divide the difference in inches by the distance in feet, and that gives the ground slope in inches per foot. QUIKRETE notes that if the site already falls more than 1 inch per foot, you may need to regrade before you form the slab.
How Much Should a Concrete Patio Slope?
There is no single agreed number, so the honest answer is a range. QUIKRETE’s patio materials call for 1/8 inch of fall per foot. Building America and ENERGY STAR guidance uses about 1/4 inch per foot, which is roughly 2 percent. QUIKRETE’s own 1/8 inch per foot sits below that 2 percent figure.
QUIKRETE is not even consistent across its own documents. The patio page and patio PDF say 1/8 inch per foot. The sidewalk and small-slab sheet recommends about 1/4 inch per foot and tells you to check local codes and conditions. A separate slab-pouring page gives 1/4 inch for every 12 feet, which is far flatter than the other two. Treat these as different numbers, not one correct figure, and confirm your local code first.
| Source | Slope stated | In inches per foot | Context |
|---|---|---|---|
| QUIKRETE patio page and PDF | 1/8 inch per foot | 0.125 in/ft | Patio |
| QUIKRETE sidewalk and small-slab PDF | 1/4 inch per foot | 0.25 in/ft | Sidewalk; check local codes |
| QUIKRETE slab-pouring page | 1/4 inch per 12 feet | about 0.02 in/ft (arithmetic) | Slab; much flatter |
| Building America / ENERGY STAR | about 0.25 inch per foot (2 percent) | 0.25 in/ft (arithmetic) | First 10 feet from the foundation |
| ADA 2010 Standards 403.3 | cross slope no steeper than 1:48 | about 0.25 in/ft (arithmetic) | Accessible-route context, not a patio rule |
The ADA cross-slope limit is listed only for context. ADA 403.3 caps the cross slope of an accessible-route walking surface at 1:48, which is about 1/4 inch per foot. That applies to accessible routes, not to a private backyard patio.
How to Set the Slope With Stakes, Strings, and Forms
You set the fall with layout, not with the concrete. The method QUIKRETE describes uses mason’s stakes, level strings, and form boards. You lower the strings on the low side, set the forms to those strings, and the forms then carry the slope through the pour.
- Drive the stakes and run level strings. Attach a mason’s string between the stakes and use a line level to set it level first.
- Find the drop. Multiply the distance between the stakes on one side, in feet, by 1/8 inch. For stakes 10 feet apart that is 1 1/4 inches.
- Lower the low-end strings. Shift the strings down on the stakes at the end farther from the house by that amount, so the line now falls away from the wall.
- Set the form boards to the strings. Use the strings that outline the project as the reference for placing the forms, so the forms hold the slope.
- Screed to the forms. Strike off the concrete with a straight 2×4 in a sawing motion, level with the top of the forms, then fill any low spots and screed again.
A Worked Drop Example You Can Check
Here is the math laid out, with each source and each hand-check marked. Start with QUIKRETE’s own patio example: stakes 10 feet apart at 1/8 inch per foot. That is 10 times 1/8, which equals 1 1/4 inches of fall, the figure QUIKRETE states for a 10 foot span.
Now compare the other numbers over the same 10 feet. At 1/4 inch per foot, the drop would be 2 1/2 inches (arithmetic: 10 times 1/4), which is QUIKRETE’s own sidewalk and small-slab figure. A 2 percent slope equals about 1/4 inch per foot, because 2 percent of 12 inches is 0.24 inch (arithmetic). Over 10 feet, 2 percent works out to about 2.4 inches (arithmetic). The gentlest QUIKRETE figure and the 2 percent figure are not the same, so pick the one your local code and site call for.
Every source points the water the same way, away from the house, and they differ only on how steep the fall should be. A patio built at 1/8 inch per foot runs flatter than one built at 2 percent, so its outer edge sits less far below the wall over the same span. Because the forms carry the slope, you fix that steepness during layout, before the concrete goes in.
What the Patio Calculator Does and Does Not Do
The calculator sizes the concrete; it does not set the slope. It turns a shape, dimensions, and a thickness into a volume and a bag count, and it treats the thickness as uniform. There is no slope field, so the fall still comes from your forms.
Take the tool’s default: a 16 by 12 foot rectangular patio, 4 inches thick, with 10 percent waste. That is 192 square feet, times 4/12 of a foot, which is 64 cubic feet. Times 1.1 for waste is 70.40 cubic feet, or 2.61 cubic yards, which the tool reports as about 118 eighty-pound bags. The slope you built into the forms does not change that estimate.
Set the forms to a steady slope, then estimate the concrete and bags for your patio from its length, width, and thickness.
What to Check With Your Local Code
Confirm the slope against the code your area has adopted, because guidance varies. Building codes commonly address drainage away from the foundation, but this article did not read the current IRC drainage text, so no slope number here comes from that code. Your building department is the authority for your lot.
A few related questions sit just outside this topic. For the slab itself, see the guide on how thick a slab should be. For walkways beside the patio, the sidewalk concrete calculator covers that shape, and the slabs and flatwork calculators group gathers the rest of the flatwork tools.
FAQs About Concrete Patio Slope
How much should a concrete patio slope away from the house?
QUIKRETE’s patio guidance says about 1/8 inch per foot. Building America uses about 1/4 inch per foot, roughly 2 percent. The numbers differ, so check your locally adopted code before you set the forms.
Which way should a patio slope?
Away from the house. Slope the finished surface so water runs toward the yard or a drainage area, never back toward the foundation. Building America notes that water pools around the foundation when nonporous surfaces do not drain away.
How do you set a patio slope with forms?
Set it with stakes, strings, and forms. Lower the mason’s string on the stakes at the low end by the planned fall, set the form boards to the strings, then screed the concrete level with the forms.
Is 1/8 inch per foot enough slope for a patio?
It can be. QUIKRETE’s patio page recommends 1/8 inch per foot, which is below the 2 percent figure some other guidance uses. If your code or site calls for more fall, follow that instead.
Does building code set a patio slope?
Not verified here. Building codes commonly address drainage away from the foundation, but the current IRC drainage text was not read for this article. Check your locally adopted code and your building department.
Will a flat concrete patio pool water?
It can. Concrete is nonporous, so water that cannot run off may sit on the surface. Building America explains that water pools around the foundation when a surface does not slope away from the house.
Does the concrete patio calculator account for slope?
No. The concrete patio calculator sizes the concrete by area and a uniform thickness, and it has no slope field. You set the fall with the forms, then use the tool to estimate the volume and bags.
Sources and Further Reading
References Used in This Article
- QUIKRETE, Building a Concrete Patio, accessed 2026-10-20.
- QUIKRETE, Pouring and Finishing Concrete Slabs, accessed 2026-10-20.
- QUIKRETE, Concrete Sidewalks and Small Slabs (PDF), accessed 2026-10-20.
- Building America Solution Center (U.S. DOE / PNNL), Patio Slabs, Porch Slabs, Walkways, and Driveways Slope Away from House, accessed 2026-10-20.
- U.S. Access Board, ADA 2010 Standards, Section 403 Walking Surfaces, accessed 2026-10-20.
Guidance on patio slope varies by source. Check your local code and set the forms to a steady fall away from the house. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated 2026-10-20.
Shakeel Muzaffar is the Founder and Editor-in-Chief, with over 15 years of experience in digital publishing and online tool development. He oversees editorial quality and formula verification to ensure accurate, practical, and easy-to-use calculators.