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Through our website are numerous articles on various stages of constructing hardscapes, including our complete guide to a paver patio and retaining wall installation. Building a raised patio utilizes both of these systems, retaining wall systems and paver or slab patios, to create a patio that will create more usable space in your backyard.
There are several aspects that need to be considered when constructing a raised patio that are outlined throughout this article. The specifications outlined here are for climates that experience freeze and thaw cycles. They are also best practices, but consulting the manufacturer’s installation guidelines based on the product you are installing is also recommended.
How to Build a Raised Patio
In terms of planning a project, a raised patio would be built when the slope of the backyard descends from the house at an aggressive enough rate to which a patio could not be built on grade. If you cannot picture yourself sitting a table and some chairs on the grass or grade to which your backyard is because your drinks would be sliding off of the table or you would be rolling backwards in your chairs, you likely require a raised patio.
Raised patio construction allows you to create a level area where you can comfortably set up a space for you to enjoy without those worries of toppling over. It is a design alternative to utilizing the most of the space you have been provided with on your property for entertaining.
A raised patio uses retaining wall systems to build up the area to a suitable height with slabs and pavers to make up the interior of the patio essentially creating a patio on top of a retaining wall border. When built according to the specifications outlined below, you can have a patio that will last you several years and parties.
Building a raised patio includes five steps: planning, excavation, base preparation, retaining wall installation, and patio installation. The base preparation step is repeated for both the retaining wall and patio installation as a two part process.
To begin with, here is the cross section of one end to a raised patio for context:
- Planning and Excavating a Raised Patio Construction Project
- Preparing the Base for Your Raised Patio
- Building a Raised Patio with Retaining Wall
- Installing the Patio
If you are unable to build a patio following the existing grade, then you are likely looking at building a raised patio so that you can have a usable space. Planning the space for your raised patio involves first deciding the approximate measurements that you want your patio to be and what products you want to use to build that patio. By defining the measurements including the height from grade to top of patio, you can then narrow down decisions especially when it comes to retaining walls.
Essentially a raised patio is a patio encapsulated by a retaining wall. The height of your raised patio may have to be taken into consideration as certain areas may have different building codes on having to build a railing if the patio is a certain height above finished grade. Knowing the height of your raised patio from grade depends on the slope of the yard and is essential to the build of the patio.
When planning your build, it is useful to consult manufacturer specifications using their retaining wall products to build the raised patio. By looking at this for a particular retaining wall block, you will be able to see the manufacturer’s recommendations on how to build the wall to compensate for different heights and surcharges being placed on that retaining wall. This may mean installing geogrid at multiple levels of that retaining wall, proper placement of drainage pipe, and having a particular degree setback with the retaining wall to compensate for the surcharge. You will also want to consider the building code in your area. You may require a railing to be installed if your patio exceeds a certain height above final grade and there may be other variables to consider.
Additionally, once you have chosen a retaining wall block and a paver or slab for the patio itself, you can then decide the final dimensions of your patio. Base this on your paver or slab plus the dimensions of the cap of the retaining wall to reduce the amount of cuts you will need to make for that project to make the patio as aesthetically appealing and efficient as possible. This is assuming that the raised patio is square. If you are planning a curved or circular raised patio, it would be beneficial to incorporate a border with your patio between the wall cap and pavers or slabs. This will help the cutting process after the retaining wall and caps have been installed and you are laying the pavers or slabs to the caps. Instead of measuring each cut one-by-one, you can lay to the caps as close as possible, lay the border pavers on top of your pavers or slabs, draw a line where you will cut, move the border pavers away and make your cut, and remove and drop the border pavers in place providing an efficient smooth cut throughout your patio. More on this later.
Calculate the dimensions of your patio, add another minimum of 6″ to each side, and spray paint your area that will be the area of excavation. Call your local utility marker which is generally free for them to come out and locate underground obstructions if any in your excavation area. From these, as well as the access available to the space, you can decide which equipment you can use to complete your excavation, what equipment you will need to rent, and if you need to have bins on site for excavated soil.
To measure the slope of your space to understand how many step downs you will need in your patio to maintain a minimum of 6″ of your retaining wall buried below grade, you will need a rotary laser, altimeter like a Zip Level, or string line and a string level for an economical choice for uncomplicated projects. If you want to learn more about how to use either of these methods, check out this article on using these different pieces of equipment to measure your slope. This measurement will allow you to understand how high your raised patio will be from the top of grade to the top of patio throughout the entire patio to make your decisions on planning from retaining wall construction to knowing whether or not you need to install a railing as well. It will also be crucial in ordering materials.
One design idea for reducing the height off of grade to eliminate the need for a railing would be to include a landing and steps coming off of the house to the raised patio itself. If the height of your steps together fall below the threshold to require a railing and that allows the height of your raised patio at the highest point above grade to fall below the threshold as well, it will eliminate the need for any railings.
When it comes to ordering materials for this, you have already done all of the leg work in terms of deciding the measurements of your raised patio and likely have a good idea of the quantities you will need to order for your project. The pavers or slabs for the patio will be based on a square footage amount of the area you are laying, but do remember the area in which the caps of the retaining wall will occupy in that. Additionally, if you have a border paver between the patio and the caps, you would need to subtract the square footage of that border against the entire patio to know how much you need to order. When calculating the square footage of the border, you would calculate the linear footage of the border and multiply it by the width of it (40 linear feet x 6″ or 0.5′ = 20 square feet). The same calculation can be applied to the caps of the retaining wall to know how much space they will occupy in the entire patio.
Retaining wall caps will be calculated by adding up the length of all of the sides and dividing by the length of each unit to provide you with the number of units you will need to order. The retaining wall itself will need some more thought process to decide how many step downs you require to maintain the minimum 6″ buried below grade that is required. We measure the length of all sides of the patio and divide by the width of each retaining wall that covers that space to provide how many units are required for one layer of retaining wall in your raised patio. Now you need to decide how many layers will be in your raised patio. For this you need to know the height of each of the retaining wall blocks and the height of your raised patio from the final grade. Laying this out will help you decide how many step downs you require, layers of retaining wall blocks you need, and how many retaining wall blocks need to be ordered.
A few considerations when ordering materials. You will want to account for an additional percentage of waste when it comes to ordering your products. This allows for pieces that may come that are chipped or broken in the shipping process or for cuts that you will be doing. In a square patio, we accommodate 10% extra in our ordering for our pavers or slabs and upwards of 20% for curved patios. Retaining wall units have less waste as any chipped pieces can be used in the buried course and you likely have minimal cuts for the retaining wall that you can easily calculate beforehand. For caps you will need to order potentially an additional one unit for every corner to accommodate cuts. Most retaining wall systems have specific corner or pillar units that you will also need to order separate from the retaining wall units themselves.
Additional materials required include base material, geotextile fabric, biaxial geogrid, perforated drainage pipe systems, and your preferred jointing compound. Base material is calculated using the square footage x depth in inches x 0.003 to calculate how many yards are required.
With the square footage of 100 for a patio, the depth outlined above for the patio base being 8″, you would need 2.4 yards of base material for the patio. The same process would need to be repeated for the retaining wall base and the area in behind the retaining wall to calculate how much additional base would be required based on the drawing above. The width of the trench for the retaining wall being 12″ minimum behind the wall + the depth of the retaining wall + 6″ minimum in front of the retaining wall block. With this dimension in terms of feet, you can multiply it by the length of all of the walls and use that as a square footage amount to complete the remainder of the calculation for how many yards of materials are required. The final calculation would be for the amount in behind the wall for the same base material to provide drainage behind the wall.
Calculating the remainder of the materials is straight forward and will be outlined as we continue through this article in terms of building the raised patio to help you decide how much you need to order of each.
Excavation continues by following the dimensions outlined in the photo above and considering your step downs in the construction of your raised patio to ensure you have the proper depth prepared for your raised patio. When excavating, you should be considering how you will be disposing of the material that is excavated whether with your own truck and trailer or renting bins and having them exchanged out. Excavation should be completed to a tolerance of 1/4″.
Preparing the base for any project begins with the subsoil. We need to ensure that we achieve proper compaction of the subgrade in order to move on to the base of our raised patio, especially if it was disturbed during the excavation process. With our clay soils, we typically will spread a thin layer of 3/4″ angular clean stone or ASTM #57 with a dusting of Portland cement throughout the subsoil and compact it using a heavy reversible compactor or a ramming compactor. These two pieces of equipment provide sufficient compaction of clay subsoils. If your subsoil is sandy, you can use a plate or reversible compactor to achieve compaction. You do not want to over-compact, as this will decrease the water penetration of the subgrade. Two passes perpendicular to one another is generally good for this step with a minimally disturbed subgrade.
The next step is to install the geotextile fabric. We typically install a woven geotextile, though in some cases we resort to a non-woven geotextile in our raised patio applications. Patios we always use a woven geotextile and retaining walls we always use a non-woven geotextile, but because a raised patio is constructed of both and integrated as one whole system that will have minimal water penetration in behind the retaining wall with proper drainage pipe installed, we are less concerned about using a non-woven geotextile in behind the wall of our raised patio.
This fabric will provide separation of our base and subgrade, filtration of water, and tensile strength to our raised patio. When installing the fabric, the pieces should be overlapped a minimum of 12″ shingling away from the foundation of the house. This ensures the water moves from piece-to-piece rather than trapping itself under the next piece. The fabric covers the entire area of the raised patio, including down into the trench of the retaining wall and up.
We can then begin to prepare the base for the wall portion of our raised patio. We generally opt of an open graded base for raise patios, though a traditional base of Granular “A” or 3/4″ crushed down to fines can also be used. An open graded base consists entirely of a 3/4″ angular crushed clear stone or ASTM #57. We prepare this in lifts according to the ability of our compactor for this step. A rule of thumb is 1″ per ever 1,000 pounds of force that our compactor is capable of.
If using an open graded base, you will want to install the drainage system using a perforated schedule 40 PVC pipe with the holes pointed downward elevated approximately 4″ above the filter fabric with a minimum 1/8″ per foot slope towards where it will exfiltrate from the system. This pipe needs to be in behind the entire retaining wall of the raised patio collecting any water that enters the system and usually exits through the retaining wall at the course that is exposed immediately above the finished grade.
Building retaining walls for a raised patio begins with knowing the dimensions of your patio and where exactly your retaining wall should land to provide the layout for your pavers. If you are unconcerned about the final look in terms of cuts for your raised patio pavers, then you do not need to be as concerned about this. However, we measure the exact dimensions of our raised patio based on the pavers we are laying and where our final caps of our retaining wall will land and ensure our retaining wall is built according to this. You also want to ensure that you are hitting the exact elevation of the raised patio. We measure where we want that to be and prepare our first block course from this, understanding the height of our blocks, how many courses of block there will be, and the height of our caps as these are usually a different height compared to the wall blocks.
We use a string line to map this out and ensure our retaining wall is level and begin to screed and lay our base course. As we build up our retaining wall, we will add geogrid every 4″ to 8″. Uniaxial is a typical geogrid that is installed in our retaining walls. This provides strength in one direction. However, in a raised patio we want strength in both directions so we opt for a biaxial geogrid and install it throughout the entire raised patio. This helps to tie everything in together and stabilize the base material of our raised patio.
As our retaining wall is built up, the base material for the interior of our raised patio can be installed and compacted in lifts one course below the retaining wall. Once you reach your desired height, your caps can be glued using a polyurethane adhesive for concrete and beads perpendicular to the wall block to allow any water under the caps to escape and not get trapped. You can then prepare the remainder of the base for the patio portion of your raised patio.
Installing the patio portion of our raised patio is like any other patio project. The only difference is knowing what you want to do with the water on the surface of the patio. In patio installations on grade, we add a minimum 1/8″ per foot slope to deal with this. However, if we do this on a raised patio we will have a high point and a low point on our level retaining wall. To combat this, you have two options. You can install a drain somewhere in the raised patio and connect that to the drain in the system. This can be installed in the middle of the raised patio and have a slight pitch in the patio towards this.
Or, you can lay your raised patio level and install a permeable jointing compound that allows water to flow freely through the joint material. If you are opting for this option, you would want to install an open graded base to allow that water to flow freely through the system, have your geogrid properly installed to stabilize your base material to prevent movement caused by that water, ensure proper compaction of the base material, and have your drainage pipe properly installed with a correct slope.
This needs to be decided beforehand and planned for in the base preparation stage of the build. After this is decided upon, you can then continue with a typical patio project install with the screed layer, laying, cutting, and jointing compound installation. In the case of a raised patio, you will not need an edge restraint as the retaining wall is your hard edge.
Building a Raised Patio Against a House
When building against a house, you want to ensure that you are not installing that patio directly against the house. Doing so will cause pressure from any movement in that patio to be placed on the foundation which will only lead to problems that you do not want to deal with. It is much better for you to spend on the extra materials and time to install the final side of a raised patio against the house with a minimum 1/2″ gap between the retaining wall and the house that can be closed off with the wall cap so that gap is not visible while on the patio.
When built properly, a raised patio will create a functional space out of a sloped yard as well as add depth to a backyard. There is a lot that can be designed in a space that has a sloping yard when it comes to creating various levels. This is when raised patios become an exceptional tool to use in your design process.