This question often arises when people install a new patio – should it be level or sloped? Believe it or not, there’s a good reason your patio needs to have a slope! Keep reading to find out more.
Why You Should Slope Your Patio
Having a level patio with a slight slope away from the house is vital. Without proper drainage, rainfall can collect in low spots and wash away the sand and sub-base beneath the patio, resulting in mosquitos breeding in stagnant water and potentially flooding the basement or lower levels.
Depending on the design, it’s essential to ensure the patio’s surfaces are perfectly level but also sloped slightly away from the house at a rate of 1/4 inch per foot (1″ every 4′ to 8′)- Get the parameters for a slope. This will ensure that all rainwater drains away from the house and not into it.
Furthermore, it is essential to use high-grade sub-base material when building a patio.
A good quality sub-base should consist of several layers, including crushed stone or gravel, for stability, followed by sand and then leveled with a concrete screed board before pouring concrete or laying pavers.
The entire area should be compacted using a plate compactor before concrete is poured.
In addition, proper leveling techniques are also essential when installing patios. Any dips, lumps, or irregularities in the patio’s surface must be repaired using a trowel-on patching compound before staining or sealing the patio surface.
Overall, patios need to be level with just enough slope so that rainwater will drain adequately away from the house instead of settling into low spots or collecting around its foundation.
Figuring out the Slope of a Patio
Figuring out the slope of a patio can be done in several different ways. The simplest and most accurate method is to measure the distance from the building to the outside edge, then multiply this by 1/4 or 0.25 for a 2% drop per foot.
For example, if you are measuring 20 feet, you will have an overall patio fall of 5 inches from one side to the other.
Alternatively, you can use a builder’s level to calculate the slope of an existing patio. To do this, place the level on the surface and lift one end high enough until it is level.
The distance lifted can then be divided by 4 with a 4-foot level or 2 with a 2-foot length (determining the fall per foot.) This method is handy if you match slopes created by existing patios or terrain features around your outdoor space.
How to Measure a Patio Slope from Scratch
To measure the perfect patio slope from scratch, you will need a
- Line level
1. Begin by placing a stake at the top and bottom of the patio where water will drain. Hammer the stakes into the ground securely to ensure they remain in place.
2. Then tie a string length between these two stakes so that it is taught and straight. Use the line level to check that the thread is level between these stakes. If not, adjust it until it is even along its entire length.
3. Once this is done, use your line level or measuring tape to measure the amount of slope from end to end of the patio surface.
- As a general rule of thumb, 1 inch per 8 feet should be sloped for patios up to 12 feet in length; 1.5 inches per 8 feet should be sloped for 12-foot patios; and 2 inches per 8 feet should be declined for 16-foot terraces(balcony) and more extensive.
- Mark this measurement on both the top and bottom stakes so you can refer back to it later when installing your patio pavers.
TIP: When measuring your patio surface with a line level or measuring tape, consider any dips or rises in the ground beneath your patio surface.
String Line Basics
When using a string line to measure, it is crucial to be precise and keep the string line taut. Here are some tricks to help get consistent measurements:
1. First, tie off the string line on a simple set-out by creating a loop at the end, then sliding your finger in and rolling it three times over the mark.
2. Pull on either end of the string line until it is taut but not too tight. Remember that even a small amount of sag can give inaccurate results.
3. Next, roll up the string line on itself and under the string line over the mark to keep it where it needs to be.
4. Finally, twist the end of the string line so that it won’t come undone when used for measuring.
Trade Secrets When Using String Line
Watch this video by Gareth Wilson, who will clarify and demonstrate how to level and measure your slope accurately, and then subscribe to his channel if you find it helpful.
Gareth Wilson. (2019, August 3). How To Set Out Levels/String Lines When Laying A Patio [Video]. YouTube. https://www.youtube.com/watch?v=eQBNSIOLhiI
It’s essential to pay attention to any bumps or irregularities along the length of your string line, as these can contribute to an inconsistent measurement.
To avoid this, use a plumb bob at each measurement end, as this will ensure accuracy. Additionally, draw chalk lines next to each side of your measurement for added reference points when checking that your measurements are correct.
When using a string line to measure, it’s essential to ensure you always have the right amount of tension on the line. If it is tight enough, you will get an accurate measurement. Too loose, and you won’t get a good enough grip.
To find the perfect balance between these two extremes, wrap the line around the nail or anchor point multiple times to ensure it is secure yet not too tight.
When pulling on the line, keep your arms straight and pull in a vertical motion – don’t pull at an angle, as this may cause the measurements to be off.
Once your desired tension and the measurements are complete, take care when releasing the pressure so that all components remain intact.
Additionally, when measuring with a looped line (e.g., when measuring angles), be sure not to twist or overlap any part of it, as this may change how it reads on the other side of whatever is being measured.
String Pro Method
- To set up a string line, you’ll need to hammer a stake into the ground at each corner of the patio site and write the desired height on the stake closest to the building. Mark a position 6″ above the desired height on the stake, then thread a string around all 4 (or more) stakes.
- Pull the string tightly and then tie it to each stake. Correct each side with a line level by sliding the string up or down at each stake until the 6″ mark is even with the string.
- The 2% slope in that direction equals the distance from the building to the outside string times 0.25. That much, plus the 6″ below the string line, is how far the patio’s edge will go down.
- For example, 15 feet is 15 times 0.25, which is 3.75 inches or 3-3/4″. Add that to the 6″ that the string line is above the starting level, and the edge of the patio will be 9-3/4″ below the string line. On top of that, the thickness of the drainage base will be added.
- Set up the 2-by-4 forms based on the size and shape of the patio, and then drive stakes into the ground to hold the forms up. Find the slope you need, which is usually 2% or 1/4″ per foot, and tie the boards to the stakes to keep that slope.
What is a Slope on a Patio?
The term “slope” refers to the incline of the patio. A good rule of thumb is to create a 1/4-inch-per-foot slope. This avoids basement flooding by draining water away from home.
Tips for Patio Installation
Here are some other things to keep in mind when designing your patio:
- When designing a patio, consider the final paver size and shape.
- Use stakes and string to mark the patio’s height and slope.
- Use a level and 2×4 to ensure accuracy.
Slopping from the Patio Experts
Patios that are less than 10 feet from a building’s foundation must slope away from the building by 1/4 inch per foot or 2%. The 2% fall or slope is needed for hardscape surfaces like pavers, wood, concrete, gravel, or other materials.
- A patio slope can be written as a ratio, a percentage, or a fraction. It can also be called grade, slope, pitch, angle, or fall.
- Patios are usually made of concrete, pavers, flagstone, brick, limestone, tile, pea gravel, or a combination of these materials. Most codes are made to keep people and buildings safe.
So, it’s essential to ensure patios are built to meet safety requirements, don’t block exits, and won’t damage the building in a way that could hurt someone.
The Grade or Slope must drop at least 6″ in the first 10 feet. Hardscape surfaces like patios less than 10 feet from a building are an exception. They must slope at least 2% away from the building.
A 2% slope is 1:48, which means 1 inch every 4 feet or 1/4 inch per foot. Aside from the building code, many home associations and communities may also have their own rules.
- The slope of a patio is measured from the highest point to the lowest. This differs from stairs, measured from the lowest point to the highest.
- So, we use the fall over the run instead of the rise over the run. How easy it is to measure the slope depends on the patio’s size. Find out how far away from the building the end of the patio is.
- Change that distance from feet to inches, then divide that number by 48. For example, a 16′ run is 192″ and has a 4″ fall or 16′ x 12 = 192 48 = 4″).
- You get the total drop from one side to the other needed to get a fall-to-run ratio of 4:198, which you can reduce to 1:48, or a 2% decline grade (4 192 = 0.02 x 100 = 2%).
- When measuring slopes over short distances, a builder’s level that is 4 feet long and a tape measure are helpful and accurate tools.
- When laying pavers and bricks that slope 1/4″ per foot, a short 6″ level or a 2′ level is often used. A long, flat board with a 4′ or 8′ level is helpful for larger concrete surfaces.
But patios may need to slope in more than one way, so a string line and string level are helpful.
How steep does a slope have to be for water to flow?
Under Section R401.3 of the IRC. The minimum slope for drainage is a 6″ drop or more in the first 10 feet from a building or a 5% grade. It is essential to have good drainage to protect structures from water damage and erosion.
Plumbing codes say drainage pipes need a slope of at least 1/4″ per foot. They can slope up to 3″ per foot or go straight up and down.
Hardscapes and patios must have a 1/4-inch slope per foot or 2% grade away from a structure within 10 feet.
How Much Should a Patio Slope?
The IRC says that any hardscape surface within 10 feet of a building must slope at least 2%, or 1/4 inch per foot, away from the building.
Hardscaping is the term for walkways, patios, and decks that are permanently attached to the outside of a building.
Hardscape includes patios: that are made of durable materials such as pavers, flagstone, brick, cut stone, tile, concrete, loose materials like pea gravel, or even wood, composite, or plastic. That means the proper slope for patios, no matter what they are made of, is 1:48, or 1/4″ per foot, or 2%.
- Many experts agree that the average slope of a patio is 2% but that individual pavers, bricks, or tiles can vary from 1/8″ to 3/8″ per foot.
- The differences are caused by packing and screeding sand to a perfect 2% grade while putting down heavy or unevenly textured stones or pavers.
Tools of the Trade for Slopping the Patio
- Use a 2- or 4-foot builder’s level to determine how steep a patio’s slope is. Put the level on the ground, lift the end that is farthest from the building, and measure how far it was raised to make it level.
- With a 4-foot level, divide the distance by 4, and with a 2-foot level, divide the length by 2. This will give you the fall per foot.
- For instance, if you use a 4-foot level, you get a 1-inch lift, 1 4 = 0.25, 1/4-inch, or 2% fall per foot. Using a 2-foot level, if the lift is 1/2 inch, 1/2 2 = 1/4, or 0.25, or a 2% slope.
A laser level or contractor’s level can help you figure out the slope, but a string line and line level are still the best tools. Check with the local utility companies to ensure there are no lines where you want to put the patio.
The Leveling and Laying of the Patio
Place, spread, and pack (R506.2.2) a layer or base of gravel for drainage 4 inches thick and 2 inches wide. Level out the gravel’s surface to parallel the slope of the forms.
- This keeps the thickness of the concrete the same and saves money. If the patio is not enclosed and heated, there is no need for a vapor barrier (R506.2.3).
- Before you pour, ensure the forms (Form: support or mold) are strong, and their slope is correct. The forms are used to smooth and level the concrete, so you must set them up and ensure they stay in place.
- Slabs must be at least 3-1/2″ thick and have reinforcement at the top. Pour the concrete screed and level it, let it set for a while, then smooth or broom finish the surface and edge the edges.
- Keep it out of the rain for 24 hours, and then enjoy. It will take about a month for the concrete to harden fully.
The ground preparation
Paver Patio The ground preparation, fill, and drainage base requirements for a paver patio are similar to those for a concrete patio, with the addition of a landscape fabric and sand layer.
Outline the shape of the patio to be dug out with a string, chalk line, or spray paint, and figure out how steep the slope needs to be.
- Remove plants, topsoil, and soil to the required depth. Add the pavers’ thickness, a 4″ gravel base, and 1″ to 2″ bedding sand.
- Level the ground or make a slope with the fall you want, and pack down any loose or added soil.
- Add, spread, and pack four inches of gravel in two-inch layers so the surface slopes towards the fall line. Set up edge restraints outside to keep the sand and pavers in place.
- Roll landscape fabric over the gravel to stop weeds from growing, and spread the builder’s sand on top of that. Put the sand where it needs to go, pack it down, and smooth it out.
- Use a rake, a trowel, or a screed board to help get rid of waves and bumps, and lay the pavers. How each paver slopes will depend on how big it is.
Depending on the slope needed to be fixed, a leveling compound, thin set, slurry, or another layer of concrete can change the pitch of a concrete patio with few or no cracks.
Another way is to dig a hole under the edge of the slab, put a hydraulic jack under it, and raise it to the new level. You can hold the concrete at the new level with sand, mud, or something else.
There are more expensive ways to raise and change the slope of a concrete patio. Professionals can do mud-jacking, or a polyurethane slurry-like liquid can be injected under the pad to lift it. The mud or slurry flows under the slab, lifting it.
How to proceed will depend on the size of the patio, the pavers, and how much the slope needs to be changed. Taking out a few pavers is often required for a minor fix.
Adding, tamping, smoothing sand, and putting back the pieces taken away.
For more extensive paver patio slope repairs, removing all the stones and putting in a new base or replacing the old one is best.
Final Thoughts – Should the Patio be Level or Sloped
When it comes to patios, the options are endless – level or sloped? Where you want to stay with a level patio, there are pros and cons. On the one hand, having a flat surface can make furniture placement more accessible and gives you more space for activities like playing cards or board games.
However, if your patio is in an area with a lot of rainfall, having a slope to drain excess water may be the best option.
On the other hand, if you’re looking for something that looks great and adds character to your yard no matter the weather conditions, then going with a sloped patio might be just what you need!
Regardless of which route you choose – level or sloped – make sure your patio will last and fit your lifestyle, budget, and requirements!