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How Deep Should A Patio Sub Base Be

Why Do The Subgrade And Subbase Allow The Concrete To Move At All Shouldn’t It Be Completely Rigid

The fact is that any soil or gravel base course is going to compress if the load is high enough, unless the slab is placed on solid rock. And in some ways that’s good, because slabs curl and if the base can deflect a little, it can continue to provide support for the slab even when it curls. But if it doesn’t provide uniform support, if the slab has to bridge over soft spots, the slab will probably crack. There doesn’t even need to be much of a load on the slab–its own weight is usually enough since a slab on grade is not typically designed to even carry the dead load. And when it does crack, that crack is going to go all the way through the slab. If the under-slab support is bad enough, you can then get differential settlement across the crack that leaves a very unfortunate bump and a very unhappy owner.

After compaction the soil density may be tested with nuclear testing equipment. Bechtel

How To Lay A Patio Yourself Prepare The Ground For Pavers Using Cement Or Not

How to lay a patio: DIY with our 10-step guide. How to prep the ground to install a patio on grass or not, using cement, or not…

Learn how to lay a patio yourself to enjoy a great looking feature that suits the style of your yard perfectly. With our easy step-by-step method, you don’t need to call in the professionals to install a patio on a grassy or other area of your backyard space. And, in no time at all you’ll have the perfect spot for wining, dining and relaxing in.

Laying a patio is a straightforward job for a keen DIYer, and is a task you could do over a weekend. The only catch is that you might need a friend to help you lift the pavers into place, whether you’re working with big or small patio pavers. 

We’ve got all you need to know to install a patio in our guide, including how to prepare the ground and lay the sub-base. We’ll even let you into the secret of laying pavers without cement…

  • Find the best patio ideas in our edit for when it’s time to decorate your space.

How To Install Walkway Base Material For Driveways Patios And Walkways

Before you begin any project that involves digging, it is highly recommended that you contact your local utility companies so they can mark off where there are any underground lines. This is most often a free service.

First, you will need to prepare the area to be paved by removing any old pavement as well as enough soil to lay your stone base , then sand bed and finally your pavers. Be sure to add the thickness of the pavers that you will be laying to the depth that you dig. Also, remove an extra 8 inches of soil beyond the planned edge of your pavers.

Once you have removed the soil you will now need to run the “sub-base” with a plate compactor overlapping each pass by 4 inches. Now evenly spread the stone over the the entire area at an approximate thickness of 2 inches and go over it with the plate compactor again overlapping the previous pass by 4 inches, lightly wetting the stone with a garden hose between layers.

Wetting the stone will make it compact faster and make it easier to rake. Repeat the last step with another 2 inch layer of stone. Next you are ready to lay the bed of sand.

The easiest way to do this is by laying down parallel 1 inch diameter pieces of conduit four to six feet apart and using a 6 to 8-foot screed board, run it along the length of the conduit. This will give you an exact 1 inch depth of sand. Any voids left by the conduit can just be filled in once you remove them.


Do’s And Don’ts Of Paver Installation: Step 2 Of 3 Base Preparation

You’ve completed your plan and pre-installation work, now it is time to get your project started.

Preparing a proper base is crucial for any paving stone project; again, we suggest you refer to the Unilock technical guide and take into account the following pieces of advice to ensure the pavers are being placed on a substantial base.

How Much Base Material Do I Need For Walkways Patios And Driveways

Complete novice needs help re. sub

Brick pavers, when properly installed add considerable beauty to your home and are very functional as well. Without the proper walkway base material laid beneath the pavers you will run the risk of them sinking or settling unevenly.

When installing pavers it is essential to install a layer of the correct walkway base material at the right thickness. This base material serves a multiple purposes, like stability and drainage as well as a level surface to install your pavers on.

Do Not Do Your Final Compaction Until You Have Cleaned The Surface

Clean all of all dust and construction debris and inspected the stones for color distribution and quality. If you need to rearrange a few stones, it is a lot easier to do it at this time than after the next stage. Once you have cleaned and inspected, tamp the stones with a compactor in all directions. A protective plate cover for your tamper is a must, as the steel plate can mar or even damage the top surface of some stones. Do one final inspection of the stones and then you are ready to apply the polymeric sand.

Do Read The Instructions Provided On The Bag Of The Polymeric Sand

There are right ways and wrong ways of applying polymeric sands and believe me, the wrong way can ruin a great job.


It is now time to get your project started. Preparing a proper base is crucial for any paving stone project; again, you can refer to the Unilock technical guide as well as take into account the following pieces of advice to ensure the pavers are being placed on a substantial base.

Proper Paver Base Installation Techniques And Minimum Base Depth

A long lasting brick patio, driveway, or walkway is the result of a properly installed base. As with anything, foundation is the key. By the time you’ve finished reading this post on paver base installation you should know almost everything you need to know about properly installing paver base.

The first thing we must do is consider the excavation depth. The determining factors include things such as paver thickness and the application of the surface whether it be for pedestrian or vehicular use. Now there are a lot of advanced factors that can be considered, however, I’m just going to cover the basics and as a rule of thumb should be all that you need to achieve a structurally sound foundation for your paver surface. So to determine the excavation depth we need to know the thickness of the paver and the necessary thickness of paver base.

Determining the paver base depth is actually very simple. For pedestrian only applications, it is adequate to have a 6? paver base depth. For light to medium duty vehicle applications it is adequate to have 10? of paver base. In some locations paver base is deemed unnecessary, i.e. Florida. However, I say paver base is necessary regardless of the location.

Installing the paver base

  • 8401 Claude Thomas Rd, Ste. 58Franklin, OH 45005

What Happens To A Concrete Slab If Support Isn’t Uniform

Concrete is very strong in compression and not so strong in tension. In a slab, tension is often created by bending. When a piece of concrete bends, it is in compression on one side and tension on the other side. A concrete slab may bend concave up if the subgrade has a soft spot in the middle, putting the bottom in tension. It may bend down at free edges or at joints, putting the top in tension. So if your entire concrete slab isn’t being supported from below, by the “soil support system,” it’s going to bend more easily and is probably going to crack.

Advice On Laying Timber Plastic Paved And Concrete Bases

A firm, level base should be the starting point for any shed or garden building. Without this the structure is likely to be assembled improperly – screw holes will not line up correctly, doors may not fit their doorways and the quality and service life of your shed could be greatly reduced.

There are a number of different options to create the necessary flat and level surface, and we’re going to take you through four of them. All are ideal to prevent water collecting around the shed floor and damaging it. These four methods are how to lay:

  • a timber base
  • a plastic base
  • a paved base, and
  • a concrete base

Both paved and concrete bases can’t be laid straight onto soft ground and so require a sub-base. A concrete base also has a further extra step – constructing the frame or edging that supports concrete while it sets, this is known as formwork. So do bear in mind that these options can take longer to build than the timber and plastic bases. We recommend only using a concrete base for larger sheds and log cabins.

Simply choose the one for you and read through the step-by-step advice on how to lay your chosen shed base.

Take time to consider a few things before building your shed base.

Start By Laying The Pavers On The Longest Straight Wall

Never assume anything is straight. Foundation walls and poured-in-place curbs are rarely straight. Always use a string line that is spaced approximately ¼” off the wall and follow that. A small gap against a wall will never be seen upon completion of project. If you start your pavers with a crooked line it will get worse as you work away from the starting point.

Is Planning Permission Required For Laying Block Paving

No. UK’s civic and town planning laws clearly state that you do not require planning permission if you are laying permeable block paving in your driveway or garden.

However, if you are using impermeable paver blocks for the purpose, there must be an area for the water to drain off into, like a border or lawn for instance. But if there is no area for the water to run off into, any paving project larger than 5m2 needs planning permission.

C A Layer Of Sand Mortar On Which The Slabs Are Laid

Complete novice needs help re. sub

The mortar mix for paving slabs varies from company to company but this is how we do it. We use sharp sand or flooring grit. No soft sand, or builders sand is used in this bed.

The mix is 8 sand to 1 cement and it is mixed in a mixer, or by hand, so it is damp, not wet. The test we do is the same as the one we do when we are floor screeding.

A handful of the mix is squeezed. It should stay in one lump in your hand without any moisture seeping out. This is a damp mix. Laying it as a bed is dealt with later in this project.

Our patio mix is 8 sharp sand to 1 cement

Ordinary Portland cement is fine for patios

There are two types of bed used generally when laying patios. One method is called dot and dab where small heaps of mortar are laid under the slab. Usually one heap is laid in each corner and one in the middle.

We do not like, or use this method at all because after a huge rainfall it is possible for water to get through the patio joints.

When this happens, it is possible for running water to cut channels in the ground under the slabs which can undermine the dots and dabs and then makes the patio loose and wobbly.

With a solid bed under the slabs the water is restricted to the joints. With dot and dab there is no bed under the joints so when you point the patio, the jointing mixture just keeps disappearing into the void.

Find Quality Paving Materials At Nitterhouse Masonry

However you lay the foundation for your project, Nitterhouse Masonry has durable pavers to match. Our paver selection covers a broad range of styles and uses, ensuring you’ll find a versatile and affordable option. As a family-owned and operated business for five generations, we understand longevity. You can trust that our pavers will provide years of aesthetic appeal and convenience after installation.

To learn more about our high-quality products, call us today at 268-4137 or locate a dealer near you.

Laying The Sand And Cement Bed For Your Patio Slabs

The bed will be approximately 50mm thick but there is no need to get it flat and smooth before laying the slab down. The bed should maintain an average thickness of 50mm but should be almost ploughed in its finished appearance. Just the same as the mortar bed when you are laying bricks.

Laying a bed of sand and cement

Dropping a slab onto the bed

Dot and Dab mortar bed

Laying the bed this way allows the high spots to be flattened out when the slab is laid down and allows some flexibility when the slab is tapped down to the correct level with the handle of a lump hammer.

Never hit a paving slab with metal to level it. Either use a rubber paving mallet or hold the metal end of the lump hammer and tap down with the handle.

Lay each slab to level along the house and leave a gap of about 12 – 15mm between each slab. This is the optimum gap for making absolutely sure you can point the joints well.

Any larger and they may crack, any smaller and it will be hard to get the mortar into the gap. See our project here on pointing paving slabs and repointing a patio for more on this.

Do Not Place Plastic Under Any Paving Application

Some people place plastic believing this will prevent weed growth. Plastic will entrap water, potentially causing other problems.

In most cases, seeds start from the top of the cracks and work their roots down. The best way to prevent weeds is to use a good polymeric sand and ensure that it has filled joints to within 3 mm of the surface.

If you are in an area that is all clay or other poor draining material, it is good practice to place a layer of geo-textile down first, then place your granular base. This will work as a mechanical barrier to stabilize and stop the clay from mixing with your good sub-base materials.

Prepare The Underneath Of Paving Slabs With A Sub

You do need to put something under paving slabs. Paving slabs should not be laid directly on to soft ground or grass. What’s crucial to patio laying success is a sub-base to provide the support paving slabs require. 

You’ll need a sub-base, which is the main load-bearing layer of your patio. The best sub-base for a patio is hardcore laid to the correct depth, along with a binding layer of sand. The pavers should then be laid on mortar made using sand and cement.

To do this, fill the bottom of your patio area with the sub-base and rake to an even depth of 50mm, then compact – you can do this by just walking over it , ensuring that you cover the entire area twice.

Can You Cut Paving Slabs With An Angle Grinder

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Uzuri Jakube

Here’s how to lay a patio in 6 easy steps.

  • 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.
  • Anastasio Wurmseer

    How Does The Subgrade/base Affect Slab Design

    We go to all this effort to get the proper soil support system and what we end up with is a single input value for the slab design. The most commonly used value is the modulus of subgrade reaction, k. This value is not directly related to bearing capacity and k does not tell the designer if there is compressible or expansive soil. What it does is indicate how stiff the subbase/subgrade is over small deflections .

    Now let’s look at why we need to know how flexible the subgrade is. To start with it’s important to understand that a slab on ground is designed as “plain” concrete. That means that we do not count on the reinforcing steel to carry any of the load. But wait, you say, there’s steel in the slab—mesh and rebars. Yes, but that steel is only there for crack control—to hold any cracks tightly together. It normally does not extend through the joints—at joints we only want to transfer shear forces, not bending moments and certainly not lateral restraint. That’s what the joint is there for in the first place, to allow lateral shrinkage in the slab.

    If the subgrade settles under the middle of the slab or at the edges, the unsupported portion can lead to cracks or slab failure.

    A poorly compacted subgrade or more load than the slab was designed to carry can result in cracking at joints. Bill Palmer

    Read Preventing Concrete Cracks for more information.

    Step 4 Place Pavers In Position And Compact

    Place chosen paving stones or blocks in the desired position, on top of the freshly prepared sand. When satisfied, run the compactor over them to bed them into the surface. This typically requires a minimum of 2 passes.

    Finally, finish off the process by running the compactor over the pavers while adding fine sand between the joints to settle the pavers and create the necessary density between them to keep them stable.

    >>IMPORTANT<< When running the machine on top of the pavers, we highly recommend using a VIBRATORY PAVER ROLLER to work your polymeric sand material into the joints, while minimizing potential damage to the pavers and the machine. Using a urethane mat on your plate compactor is another good option. Protecting your material from chips, cracks, and breaks is essential, especially when using synthetically manufactured pavers common in North America. 

    The basic principle of compacting any material is the same: put the material down in layers and compact between each one.

    Of course, we aren’t saying this is the only way to lay and compact materials because every situation is different.

    With experience and understanding of compaction equipment, various environments, types of stone, aggregate and other materials available, you’ll be able to effectively tweak this best practice process effectively, to achieve the best results for your project.

    How Deep Does A Patio Foundation Need To Be


    4.3/5patio foundationsneedfoundationpatio shouldwill need

    Highways 150mm +

    Furthermore, how do you lay a patio without concrete? Although building your patio over a concrete slab helps to ensure it won’t settle unevenly later, you can build a patio without cement. By laying flagstone, tile, brick or other sturdy, flat pavers on a well-prepared base, your patio will be less expensive and more water-permeable.

    Simply so, is laying a patio difficult?

    Lay a patio now and you’ll enjoy the benefits each time you’re out in the garden. It’s not a difficult job, so put aside a weekend and you’ll soon be entertaining friends, or enjoying a well-earned rest on your new patio surrounded by pots and plants.

    How do I build a patio base?

    Here’s how to lay a patio in 6 easy steps.

  • 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.
  • Step 1: Ask Yourself The Boring Questions


    What is the drainage system surrounding the area you want to lay the patio?

    You will need to address this as drainage will prevent unsightly surface water and minimise any foul smells which can be created from bacteria growth in standing water.

    All of the paving slabs will need to be laid with a slight slope, around a 1 in 80 fall. This is so that pools of water don’t form on the surface of your patio. That means that for every 80cm your patio should fall by 1cm. The fall may vary dependent on the size of your patio but this is the optimum level.

    This fall creates a natural run off, so should ideally be directed away from a house. However it may be necessary to direct this water elsewhere, dependent on where your drain is, and to avoid a sodden lawn!


    Are there any cables running below the area I wish to paveover?

    It isn’t a problem to pave over cables, its whether you will need access to the cables at a later date and would be you be prepared to dig up all your precious paving.

    If you do have cables running below, one solution would be to safely secure the cables and then lay the patio onto a layer of sharp sand rather than mortar and use small aggregates or sand in between the gaps. This method allows for the paving to be freely lifted up and moved if needs be. However this isn’t a method we would recommend as the movement of slabs is likely.

    Subgrade And Subbase Construction Sequence

  • Removal of surface vegetation and topsoil
  • Excavation of high spots of grade
  • Prepare and Compact Subgrade
  • Brought in materials if natural soil bearing capacity is poor.
  • Compact subgrade fill
  • Gravel and sand compacts best with a drum roller or a vibrating plate compactor.
  • Cohesive soil can best be compacted using a vibrating sheepsfoot roller or a rammer.
  • For small projects, or around the edges, pipes, or columns, a plate compactor provides good compaction for sand or gravel.
  • Fig. 4: Subbase Compaction

    How Can I Make My Paving Slabs Look Better

    To create our patterned look, simply stain different slabs with the different shades in an alternating pattern. Or you can apply a mix of shades to the same slabs by layering them on until you’ve got the shade you’d like. If you’d like a darker stain, just add more coats.

    You might be interested: Readers ask: How Many Garden Slabs Do I Need?

    Accurately Measure Required Base Material

    What depth of base materials is necessary? There is no absolute rule to determine how required depth, however recommendations vary by use. The guidelines are 4 to 6 inches for pedestrian walkways and 8 to 12 inches for driveways. Local soil conditions also impact depth needs. Generally, clay bases need to be dug deeper to facilitate drainage.

    Consult your local dealer for further guidance.

    How To Find Cubic Meters Of Base Material

    Finding the cubic meters of sand and gravel needed is very similar to the steps above, with slight changes:

    • Measure the length and width of the patio in centimeters
    • Multiply the length and width to find the area in square centimeters
    • Multiply the area by the gravel depth in centimeters to find the volume in cubic cm
    • Divide gravel cubic cm by 1,000,000 to find the volume of gravel in cubic meters
    • Multiply the area by the sand depth in centimeters to find the sand volume in cubic cm
    • Divide sand cubic cm by 1,000,000 to find how much sand is needed in cubic meters

    Subgrades And Subbases For Concrete Slabs

    A well-compacted subgrade keeps construction out of the mud and provides uniform slab support. Lippincott & Jacobs

    What lies below your concrete slab is critical to a successful job. This is no different than the foundation for a building. A slab on ground by definition is not intended to be self-supporting. The “soil support system” beneath it is there to support the slab.

    Making Sure The Water Runs Off Your Patio

    The image above shows the trench along the house wall. In the centre of this trench we bang in a small wooden peg or steel pin and leave it 25mm proud of the bottom.

    Using a spirit level we bang in more pegs, about a metre apart, all along the trench so we know our trench is level as each peg should be showing about 25mm above the ground.

    Now we start excavating away from the house banging in pegs every 1 metre and using the spirit level to identify a slope of 15mm every 1.5metres as described above, which is the correct fall on a patio.

    Use your level to get a fall on the patio slabs

    A little trick of the trade for getting this slope or fall easily is to set up two pegs 1m apart.

    The required fall over 1 metre is 10mm so set the pegs level and then bang one down 10mm.

    Put the spirit level across them now and note where the back of the bubble comes to on the level.

    You can see from the image above that our bubble is up against the black increment line on the level.

    This would be easy to use as every peg we banged in we know that if the bubble is on the back line we have the same fall or slope.

    If yours does not work out quite so simplistically, just stick a piece of electrical tape or masking tape in the place where the bubble shows a fall of 10mm per metre.

    Once the area is dug out we can start laying slabs. The first row to lay is along the wall of the house, but as said before, 100mm away from the actual wall. This line of slabs needs to be level.

    How To Find Cubic Yards Of Base Material

    Sub Base Buildups

    To estimate the cubic yards of sand and gravel needed for a paver base follow these steps:

    • Measure the length and width of the patio in inches
    • Multiply the length and width to find the area in square inches
    • Multiply the area by the gravel depth in inches to find the volume in cubic inches
    • Divide gravel cubic inches by 46,656 to find the amount of gravel in cubic yards
    • Multiply the area by the sand depth in inches to find the volume in cubic inches
    • Divide sand cubic inches by 46,656 to find the amount of sand in cubic yards

    The Cost Of Laying A Patio In The Garden

    Building or laying a patio or even laying decking will probably be the most money you spend in the garden.

    Indian Sandstone slabs come in a range of sizes and types as do other slabs, so buy the best you can afford

    With regard to laying paving slabs and the actual slabs you will be using, you will, as with all products in the building trade, only get what you pay for. It is possible to buy cheap concrete slabs for little money in deals on the internet etc…., but beofre you do, just consider the following.

    With cast concrete slabs, the concrete is poured into a mold and vibrated to settle them flat. This process makes a wet cement layer to the top of the slab and this forms a cement skin on top.

    The skin is very thin and a couple of power washes later, the stone in the slab becomes visible and unsightly.

    Cheap concrete slabs are usually pretty poor, and additionally, poor quality slabs usually have lots of air bubbles in.

    If water gets into these air pockets and freezes when its cold, this ice expands and forms tiny little cracks in the concrete, which in turn fill with water and this process continues until the paving stone literally falls to pieces but on the journey the face of the slab “blows” off making the whole patio very unsightly.

    This process is called Freeze-Thaw action and more about it can be seen here.

    Cutting Paving Slabs Using A Disc Cutter

    There will be obstacles in the garden, like manholes and sheds, that you need to cut slabs round. This can easily be done with an angle grinder or disc cutter.

    If you have only one patio to do, it would be more cost efficient to hire a cutter. If you have more to do, you can buy one.

    Use a petrol 300mm disc cutter for ease

    Please wear all the appropriate safety equipment when using an disc cutter and check to make sure you are using stone cutting discs, not metal.

    It is a weird fact in the building world that a cutting disc that is used for cutting stone, can also be used for cutting metal, but a cutting discs for metal will not cut stone.

    If you have a lot of slabs to cut it is really worth getting a diamond cutting disc as they are so much quicker and do not wear out. A diamond disc will come with a 300mm cutter if you hire one.

    A hired petrol disc cutter will have a water feed to the wheel. This is to keep dust to a minimum and allow the blade to last a little longer by keeping it cool. This is now obligatory on diamond disc cutters

    Diamond discs will cut patio slabs quickly

    Patios do not have to be all on one level

    When you have laid the patio to the end of the garden, see our foundations project, and also check out our laying bricks and blocks project and, additionally, our retaining wall project to finish it off and enjoy the summer.

    All project content written and produced by Mike Edwards, founder of DIY Doctor and industry expert in building technology.

    How Deep Should I Dig For A Stone Patio


    Remove any turf, plants or paving and dig down to a depth of about 150mm to allow for the foundations. To lay a solid base for your paving slabs, first put a layer of hardcore to a depth of about 50mm-80mm over the area of your patio. Distribute the hardcore with a rake, evening out bumps.

    Subsequently, question is, what do you put under patio stones? Sand. A thick layer of sand below your pavers will cushion them while allowing water to flow through properly. “Sunset” magazine notes a base of sand alone is not ideal for paths or patios with heavy traffic because the material can shift. But it can work well for areas you‘ll only use occasionally.

    In this regard, how deep do I need to dig for block paving?

    The excavation depth for a typical domestic driveway is 200-250mm below finished paving level, based on 100-150mm sub-base, 40mm sand bed and 50mm block.

    How deep should you dig for interlock?

    How deep you need to dig depends on the combined thicknesses of the gravel base, sand layer and your pavers, which vary — as does how you will use the area. For example, the recommendations are to provide a base of gravel 4-6 inches thick for average pedestrian traffic, which requires you to dig about 7-9 inches deep.


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