Water the ground deeply the night before starting the flagstone paver project so the clay soil softens and is easier to dig. Unfortunately, if you have clay-heavy soil, then you may run into difficulty when pouring a slab. Fill in the gaps between the stones with your choice of coarse masonry sand, pea gravel or decomposed granite. Flagstones work well as a surface stone for patios and walkways because they have a flat surface. Remove sand so the stone rests level. Step 2. Keep the top of the concrete slab moist to help ensure even curing. I'm laying a patio which I wan to adjoin the house. For example, a flagstone might be perfectly flat on one side, but if you flip it over, part of the opposite face sits up higher than the other half. A waffle-like grid (known as grade beams) is placed under the slab to help enhance the slab’s strength and … Laying turf on clay soil needn’t be too much of a headache. Silt – Silty soil can be smooth to the touch and retains water longer because of its … Make the center of the excavated area one to two inches higher than the outer perimeter and slowly decrease the grade to the outer edges. Slabs made of concrete can be large or small, and have a variety of uses around the home. She received her Bachelor's degree from West Virginia University. The next mistake to avoid is failing to make your chosen sand … If temperatures are above 80 degrees Fahrenheit, wet the concrete several times per day with a garden hose or sprinkler. The soil below should be at a slight grade so that when water drains through the sand and gravel and reaches the poorly draining clay soil below, it runs off of the soil instead of forming pools beneath the rock. Here's my questions: Use a scrap two-by-four as a screed to spread the sand evenly. Mix the concrete according to package directions, using as little water as possible so that the concrete mix is wet, but not saturated. Geotextile Layer. A former cake decorator and competitive horticulturist, Amelia Allonsy is most at home in the kitchen or with her hands in the dirt. Clay soils are made up of 40% water, but trees can change this amount differently throughout the year - causing the soil to shrink or swell with enough force to affect the foundations of a building and so it's vital that the foundation is the … When stone flags are laid to town … In addition, when the paving will go over silt or clay soils, a layer of geotextile fabric is recommended on top of the soil subgrade. In many cases, this will involve installing concrete piers or screw piers into the ground underneath the footing beams on the slab for added stability and support, to a depth sometimes below the depth where soil moisture variations are minimal. A stone base layer 12 inches thick allows water to drain and supports the flagstones. Aim to leave around 20mm between each one. Allow the concrete sufficient time to settle and begin to cure before troweling the top surface of your slab. One method is quick and easy but it will be hard wearing on your decking. Control joints should be placed every 4 to 10 feet across your slab, depending on its size. While you may want a smooth slab surface, adding control joints that are approximately 1 inch deep gives you more control over where the cracks occur and helps to hide them from view. Disassemble the frame from around the concrete slab after five to seven days have passed. This type of soil is generally more fertile than sandy soil, but it will always need amendment of some sort if you want to grass … The type of earth you lay foundations on can have repercussions for your client’s homes for decades after it’s been built, and for the course of its whole life. Always call a utility locator service a few weeks before you dig so they can mark the location of underground utility lines. The other is more difficult but your decking will stay healthier for longer. You don't need to mark out the area perfectly, just spray in the approximate area where you wish to install the flagstones. You can purchase restraints specifically for this purpose or push benderboard strips against the edges and drive stakes beside the boards to pin them in place. If desired you can add a wire mesh as well, though the rebar will provide the largest boost to concrete strength. … If preferred, you also can create a barrier by placing plastic sheeting on the ground inside the frame instead. The sand and rock layers must be perfectly level before installing the flagstones. If you lined your frame with plastic sheeting, support the rebar with concrete bricks to ensure that concrete material makes its way under the bars. Monitor the concrete and wait for the water to disappear from the top of the slab, then trowel the concrete as soon as possible. 4) Riprap. Riprap are large, irregular-shaped rocks … Using a dryer final mix results in a stronger slab and prevents water absorption by the underlying soil. Gently tap them into the damp sand with a rubber mallet. The soil should have a very slight grade to encourage water to run off away from the paver area. Build a wooden frame for your slab, using a carpenter's level to make sure that the walls of the frame are leveled properly. Excavate the soil within the marked area to a depth of 13 inches to allow for a 12-inch gravel base and 1 inch of sand. Unlike perfectly symmetrical paver stones that fit tightly together, flagstones look best with gaps between stones that highlight the irregular shapes. However there are a couple of points that should be mentioned in regard to the laying of clay pavers. You can also jiggle the stones a bit to settle them in the sand. With proper preparation, however, it's possible to pour a slab on clay soil without encountering these problems. You can choose irregular-shaped or straight-sided options in these thin stones. When clay is moist, it is very pliable, and can easily be moved and manipulated. If the clay soil is very soft, excavate the soil to a depth of several inches and mix in gravel to create a firmer base for your slab. Mark out the area for the flagstone patio or walkway, using several garden hoses or ropes. A floating slab spreads the structure weight over the entire base instead of at strategic supporting columns. Excavate the soil within the marked area to a depth of 13 inches to allow for a 12 … Born in West Virginia, Jack Gerard now lives in Kentucky. These extreme changes put a great deal of pressure on foundations, causing them to move up and down, and eventually crack, making clay a poor soil for support. © Copyright 2020 Hearst Communications, Inc. … Clay soils are the polar opposite to sandy soils. Clay soil has poor drainage, and it softens and erodes when it gets wet, so flagstones can shift and break with regular foot traffic. How to Lay a Concrete Floor Over a Gravel Basement. The patio is to be 4m x 3m. Moisture variations tend to be lower at greater depth in clay soils. In most installations, it is important to slope the paving so that it drains effectively. Also the ground is heavy clay soil. Use a spade to cut around the painted guide marks and use a flat shovel to scrape up the soil layers. You will need to start by laying down pegs and string to mark … For flexible construction, clay pavers are laid in exactly the same way as concrete blocks – a screeded bed of grit sand is prepared, the blocks are laid by hand, cut-in and compacted. They are cold and don’t drain well, as the water stays in the tiny pore spaces between the minute clay particles. If temperatures are cool to mild, cover the concrete with plastic sheeting to conserve moisture. The term ‘reactive soil’ may conjure up images of radioactivity beneath the … If you choose to install the flagstones so they rest above soil grade, you must install edging restraints to keep the pavers and filler material between pavers from shifting side to side. Lay a carpenter's level across the sand base to check for level and move the sand around as needed to make a level base. Remember to use a spirit level on each and every slab once placed, if not level use a mallet and wooden block to hammer until it … Lay the level across the stones periodically to keep the patio or walkway surface as level as possible. The terminology used for soil support systems, unfortunately, is not completely consistent, so let's follow the American Concrete Institute's definitions, starting from the bottom: 1. Preparing the site. Lay flagstones directly onto the sand base layer, starting at one corner and working your way to the other side. The first is to incorporate sand into your soil to give it drainage. To get the necessary slope (1:60) the surface of the patio will need to be less than 150mm from the dpc - about 100mm is the best I can do. Moisten the sand with a hose so that it is easier to spread, and create a completely flat layer on top of the base. Lay your bricks in Set the bricks down one by one, starting on the near side before working outwards. As they are shallow in-depth, they could ideally be used in specific … Dig 150mm into your patio area; Lay a compacted sub-base of 100mm; Cover the area with 40mm of concrete mix; Lay paving slabs 15mm into the concrete with a 10-15mm gap; Leave to set for at least 24 hours; Fill the gaps between the paving slabs with concrete mix; What … Sand, gravel or polyethylene plastic sheeting. The base should extend 8 inches beyond the edges of the paving. Her work has been published in the San Francisco Chronicle and on other websites. Concrete shrinks as it dries out and this usually results in cracks. Compact this surface as well; this will be the final surface on which you set your slabs. How to Fix Pitted and Cracked Garage Concrete, How to Pour Concrete Landscape Curbing by Hand, The Family Handyman: How to Pour Concrete, Schlatter Family Site: Pouring the Concrete Slab. © Copyright 2020 Hearst Communications, Inc. Set your paving slabs on top of the sand in your designated … Slab-on-grade foundations are another good choice for clay soil. Continue spreading and compacting the crushed rock in 3-inch layers until the base reaches a total depth of 12 inches. The floating slab is sometimes called a raft foundation, and they’re generally constructed on soil with high proportions of sand, clay, or water. Smooth the surface and begin laying down the slabs for your shed starting from one corner and working your way out. Transform that sunny patch in the garden to a patio area where you can sit with friends and family and enjoy a cold drink in the summer sunshine. Level the are where the slab will be poured with a rake. Filter fabric is designed to separate the base material from the underlying soils. A former nationally ranked sport fencer, Gerard also spent several years as a fencing coach and trainer. Here’s how to lay a patio for beginners in 6 easy steps. Over time and especially during rains, the native soils could eventually mix with the compacted class II base material and eventually weaken the paving system. A well-designed slab can withstand the pressure of the soil contracting and expanding allowing the structure it’s supporting to remain stable. Subgrade—this is the Building Connection investigates the issue of reactive soils and what you need to know. Clay-heavy soil poses a greater challenge. The clay can compress under the weight of the concrete, causing the slab to shift or sink over time. Clear and level the area where you plan to pour the concrete slab. Southern California soils commonly are clay or silt based. Step 3. Law a few more pieces of flagstone next to the piece you just set in the dirt. Use the back side of a bow rake to push the crushed rock around. This can make riven slabs more difficult to lay but the same technique as flat slabs can be applied (see below) with the spirit level reading being taken from where it touches the slab. Clear and level the area where you plan to pour the concrete slab. If you lay paving on soil with no supporting hard base, it will eventually deform and need … The choice of laying methods depends on the personal preference of the contractor/specifier, the type of bedding that is chosen, and the types of flags being used. This is a type of plastic fabric much like landscaper’s fabric. There are two ways you can lay decking on grass. Measure the depth remaining along the sides of the area and subtract that number from the total excavated depth to determine how much rock you have already spread. The concrete should be at least 90 percent cured by this time and will need no additional support from the frame. Either method will prevent the clay soil from absorbing moisture from your concrete. Make it Compact. How to Install Concrete Bricks for Lawn Edging, How to Build Your Own Flagstone Mowing Strip, How to Make a Garden Path With Slate Slabs, Paver Search: A Guide to Installing Flagstone Pavers, University of Minnesota SULIS: Paver and Brick Installation, This Old House: How to Lay a Bluestone Patio, Pave Tech: Installation Guide to Paver Walkways and Patios, How to Use Fieldstone As a Border Around Gardens, How to Make a Walk With Pea Gravel and Concrete, How to Prepare a Yard for Landscape Stone, How to Lay Flagstone With Crushed Bluestone Over Concrete. Soil, even when compacted morphs with time, weather and pressure. There are two acceptable methods of laying flags - individual bedded and screed bedded. Cut the 1-by-6-inch pieces of lumber to frame the slab area with wood to make a concrete form. A writer and editor with more than 10 years of experience, he has written both articles and poetry for publication in magazines and online. We’ll talk you through both methods. Add drainage. You can lay a weed membrane over … Stone patios require a base layer of compacted stone and sand to keep the pavers from shifting, but the thickness of the base depends on the soil type. The slabs can be seen to be sloping away from the house and a slope, or fall, of 15mm per 1.5 metres is a good fall for a patio. Spread crushed rock -- containing roughly equal parts 3/4-minus stone (stones that are 3/4 inch or less in size) and stone dust -- over the area in 3-inch increments. Laying concrete slabs or even a driveway on expansive soil without careful engineering and adequate drainage can … mix of sand/cement about 4:1, rake level and stamp down then lay slabs as normal on mortar of your choice. If the soil is predominantly organic, like a rich gardening topsoil, several inches of soil will need to be excavated and replaced with a more granular fill soil. A material like clay or certain types of granite with lower porosity don’t work well within the soil, but they do make ideal materials for support terraces or retaining walls. How to lay decking on soil or grass. The more compressed your soil is, the less likely it is to cause significant damage to your concrete slab as a result of continued compression, and the more overall weight it can support. Take extra care when excavating foundations in clay soils, especially if there are trees nearby. This is a bad idea, under the cement which supports the paving there needs to be a hard surface. There are two ways to go about preparing your clay soil for laying the turf. Fill the base of the sub-grade layer with gravel or limestone. Drive wooden stakes into the ground on the outside of the frame, securing the frame to the stakes with nails or screws to hold it in place. Remove or add some sand underneath the stones to adjust level and, if needed, to accommodate bumps or grooves in the flagstones. Compress the clay-heavy soil in the area where you plan on building the slab using a soil tamper or yard roller. Spray landscaping spray paint directly beside the hoses to transfer the outline to the soil. Top the paver base with a 25 mm (1 inch) layer of sand. Create a barrier between the concrete and the soil by pouring a 2-inch to 4-inch layer of sand or gravel into the bottom of the frame. In fact, clay soil can have its advantages, as it holds water well and is rich in nutrients. ConcreteNetwork.com: How Can We Improve the Subgrade? How to Pour a Slab on Clay Soil Step 1. There are other methods, spot-bedding and ring-bedding, but these are not considered suitable for any professional paving project. Add the paver thickness to the total depth if you want the flagstones to rest even with the surrounding soil grade. It also can leach moisture from the concrete itself, resulting in uneven curing and a brittle base. Spread a 1-inch layer of coarse masonry sand over the crushed rock. Choose stones with shapes that fit together together so you leave no more than 1 to 1 1/2 inches of space between stones. Tap the flagstones with a rubber mallet to set them firmly in the sand base layer. Many people want to know if they can lay the paving directly on to soil. Laying turf on clay soil mixed with sand. This will create the … Use a carpenter's level to check the rock layer for level frequently, and add or remove rock as needed to achieve a level base. Place 3/8-inch or 1/2-inch rebar inside the frame to provide additional strength to your concrete slab. Compact the 3-inch layer with a plate compactor; a hand tamper works well on small areas such as walkways.