Step by Step: How To Build A Gravel Driveway - Factor Geotechnical Ltd. (2024)

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FREE GRAVEL DRIVEWAY CONSTRUCTION DRAWINGS
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As a geotechnical engineering company we hate to see do-it-yourself driveways fail when just a few simple changes and proper planning could have made all the difference. In this article, we’ll walk you through how we would build our own gravel driveway that would stand the test of time.

So, if you’re a homeowner with enough know-how to be dangerous and a desire to avoid paying a contractor for easy work you’re in the right place. This step by step guide will cover topics from how thick your gravel driveway should be to how to lay your gravel driveway grids and everything in between.

Take a look at the step by step overview below, then navigate to the corresponding number below for additional help on each step.

Step by Step Overview

1. Plan your driveway footprint
2. Plan your driveway cross section
3. Determine the amount of construction materials you will need
4. Excavate the thickness of your driveway cross section from the footprint
5. Inspect the soil inside the driveway footprint
6. Prepare the subgrade for construction
7. Place geotextile and geogrid
8. Install any gravel driveway edging materials
9. Plan your gravel deliveries
10. Place and compact your base layer of gravel
11. Place and compact your surface layer of gravel

Click here for
FREE GRAVEL DRIVEWAY CONSTRUCTION DRAWINGS
to help you build your driveway

1. Plan Your Driveway Footprint

Use stakes to lay out your new driveway. By wrapping twine tightly around the stakes and attaching the stakes around the border of the driveway, you can more easily visualize, measure, and excavate your newly planned gravel driveway.

2. Plan Your Driveway Cross Section

If you want to optimize this, you should really speak to a geotechnical engineer that can provide a cross section specific to the soil conditions on your site. Depending on the size of your driveway and how many materials you’ll need, this may be a cheaper approach.

If you’d rather skip the engineer and just build a driveway that may be thicker than necessary, then read on.

A typical, safe gravel driveway cross section is approximately 300 mm (12″) or thicker and consists of two separate layers: the base and the surface layer.

If you contact a geotechnical engineer they should be able to reduce the thickness of your driveway, and recommend cost effective materials such as geogrid to further strengthen your driveway.

2.1 The Base

The gravel base layer is the foundation of your driveway and should be the thickest layer of the entire cross-section. A thickness of around 200 mm (8 inches) is recommended for the base layer. The base should consist of well-graded crushed gravel with a fairly large maximum diameter.

In Calgary, we typically recommend an 80 mm crushed gravel for the base layer of gravels in a gravel driveway.

It is important that the base remains free draining, and does not collect water. Geotextile filter fabric is required between the native material on your site and the base gravel.

2.2 The Surface

The gravel on the surface of your driveway should consist of a small diameter crushed gravel. A 20 mm crushed gravel is the ideal choice for the surface layer.

You want an angular gravel (the more more broken rocks a gravel has, the more angular it is said to be) because the individual pieces of gravel in your compacted driveway will interlock and form a more cohesive and solid surface for you to drive on.

The surface layer should be at least 100 mm thick.

2.3 Other Materials

As mentioned in Section 2.1, you will need a geotextile filter fabric between your base gravel and the native soil on your property. The filter fabric works as a barrier between your gravel driveway, and the materials under it. Without a geotextile, every time you drive over your driveway you are slowly pushing your driveway into the native soil on your site. Eventually, your free-draining gravels become filled with materials that stop water from flowing through it, which can turn your awesome driveway into a muddy, pothole-filled mess quickly.

Other materials that can be considered to improve the strength of your driveway, assist your build up a slope, or improve other aspects of your driveway are listed below.

3. Calculate Quantities

Depending on the shape of your driveway, this is a pretty simple task, especially if you have staked and roped your driveway.

Simply take a piece of paper, look at your staked driveway, and sketch it out. It doesn’t need to be perfect, just make sure you get the approximate shape.

1. Now, just measure the length and width of your driveway and mark it on your drawings. Now multiply those numbers together to get the total area of your driveway.
2. To get your base gravel quantity, you’ll take that total area you just calculated, and multiply it by the thickness of your base gravel layer.
3. To calculate your surface gravel quantity, take that total area you calculated, and multiple it by the thickness of your surface gravel.
4. To determine the amount of geogrid or geotextile you need, you can simply use that same area calculation you used in Step 1.

Make sure to account for compaction factors for your gravel. A typical number is approximately 0.88 – meaning you will need approximately 12% MORE gravel than the volume of your cross section (due to compacted gravel being more dense than uncompacted gravel). Ask your gravel supplier for their recommendations as all gravel is different.

You should add 5% or so to these calculations to account for any small mistakes you may make, as well as the effects of compaction and other small changes from the calculator to the real world.

4. Excavate The Driveway Footprint

This is the hard work part. You may want to hire a well respected local contractor for this as they’ll have experience in driveway construction and they’ll have some heavy equipment that will make this step go much faster.

Regardless of whether or not you’re going to hire a contractor, I hope you’ve staked your driveway out so you can accurately excavate the footprint of your driveway and not accidentally make it too big or too small for the material quantities you’ve determined.

First, you’ll want to excavate a depth equal to the thickness of the gravel base and the surface gravel layers added together (approximately 300 mm if you’re using the thicknesses in this article). You may need to go deeper, depending on the soils you see at this depth.

If you’re planning on installing edging to contain the gravel, you can excavate space for whichever type of edging you’ve chosen now.

5. Understand Your Property’s Soil

The key to building a long-lasting driveway is understanding your property’s soil conditions. Now that you’ve excavated to the elevation of the base of your driveway, you should take a quick look.

Is it mainly a gravel or sandy material? You’re in luck! You will be able to avoid the issues most people have to spend their time on. A gravel or sandy subgrade will drain well and is not likely to have major issues with heaving, freeze/thaw, or settlement. A geotextile is still recommended, but you can probably get away without one, if you feel like cutting some cost.

Is it silty or mostly a clay material? Sorry, there might be a few extra steps and costs to complete your project – geotextile is a MUST for this scenario and geogrid is also recommended.

Is it organic and black? You might want to call a geotechnical engineer. Feel free to reach out to us if you’re in Alberta or BC!

If you’re from somewhere else or feel like going it on your own – you’ll need to excavate all the black soil out. Start in a small area to see how deep it goes first. If it goes very deep, you should talk to a geotechnical engineer. An organic content test can provide guidelines as to how much of the soil needs to be removed.

In any case, a thicker layer of surface gravel is needed if your soil conditions are softer or finer-grained.

A common trap that outdoor DIY’ers fall into is assuming that the dry soil they see in the summer is as “hard as concrete”. Sure, your soil is in great condition in the heat of the summer, but how does it hold up to a torrential downpour in the spring? If you want to build a driveway that doesn’t fall apart at the first sign of rain, you’ll want to take a good look at your soil when it’s both wet and dry.

6. Driveway Subgrade Preparation

Once your driveway is stripped of all undesirable materials, you should test out the strength. On construction sites, this is called a proof-roll. Its usually done with a fully loaded dump truck, but get creative and try driving over it with your truck or whatever might be the heaviest piece of equipment around. If you see any areas that are rutting worse than other locations, it may be wise to remove that soft material and replacing it with a well compacted gravel, or consider calling a geotechnical engineer.

The last thing to do before your subgrade is complete is to grade it for drainage. You’ll want a crowned profile (peak in the middle and slope out to the sides) or a cross-slope (one side of the driveway is higher than the other). Avoid any dips or areas where water might get caught. Even though it may not seem important to have your subgrade soil shed water quickly, it can make a big difference in the lifespan and required maintenance for your driveway.

We see a lot of blogs only recommending that the surface gravel be built with a crown. While this does help, the real key is making sure that the native soil below the gravel driveway is crowned or sloped to one side. Water moves through gravel easily, but can just sit inside the gravel that is your driveway. Especially if the native soil on your site is a clay or silt material.

7. Geogrid or Geotextile Placement

As discussed above, a lightweight, nonwoven geotextile filter fabric is a good idea and we recommend always using one. It keeps your driveway separated from the underlying native soils that can plug and contaminate the carefully screened gravels you buy from your local gravel suppliers.

Is your native soil fine-grained, like clay or silt? You 100% need a geotextile filter fabric and probably should use some biaxial geogrid as well (don’t use uniaxial geogrid, that type of geogrid is intended for retaining walls).

Is your native soil sand or gravel? You’ll probably be okay with a biaxial geotextile, but your driveway will last longer with geotextile. You likely don’t need to use geogrid in this scenario.

Once you’ve selected your geogrid and geotextiles, you’ll need to place them. See below for a brief step by step instruction on how to install geotextile. Geogrid is installed in the same way, just without going up the sides of your excavation.

1. Roll the geotextile across the driveway so that it goes up the sides of the excavation
2. Use large galvanized staples to fasten the geotextile to the subgrade, making sure it is flat and has a bit of tension in the fabric
3. Roll out another row of geotextile so that it overlaps the first by 150 mm (6 inches)
4. Repeat step 2
5. Continue until your entire driveway base is covered

Take a look at some of our other articles for more information on why a geotextile can save you a lot of money and headache in the long run. It’s important NOT to use landscape fabric. It is not the same as geotextile filter fabric and does not work in this application.

8. Install Driveway Edging (if desired)

Driveway edging isn’t necessary for a gravel driveway, and depending on the aesthetics and layout of your home and property, you may not want to install it.

If you’re wondering what it does for a gravel driveway – basically it just defines the borders of your driveway and stops the gravel from moving around so much and spreading to areas you don’t want it to go. It will reduce your maintenance a bit, and looks nice, but not a big deal.

9. Plan Gravel Deliveries

Once you’ve got everything in order – your geotextile and geogrid has been laid, your edging is done, your tools are ready – it’s time for gravel.

The first gravel you’ll want to order is the bottom layer of gravel – the larger diameter gravel of the two we recommended in Section 2. (We recommend a 80 mm (3 inch) crushed gravel or something around that size for the base layer).

So, just call a few gravel companies up with the quantities you’ve calculated in Section 3 handy and let them know what you need, where you need it, and how much of it you need. Pretty simple stuff in this section.

One tip: good dump truck drivers can actually unload their gravel while they’re driving, effectively spreading it across your entire driveway without you even lifting a finger. Some companies might also offer a slinger truck, which can spread your gravel for you (often at an additional fee).

For your first order of gravel, you should aim to fill approximately half of your base layer so you can compact it and make sure its good and hard before getting a second delivery of the 80 mm to complete the base layer.

10. Place and Compact the Base Gravel Layer

You’ll want to install the base gravel in two layers so you can get it properly compacted. Remember, this layer is the foundation of your driveway and is key to building a long-lasting, quality gravel driveway.

If you can, get the dump truck or slinger truck to spread the gravel for you. If not, get out of the rake, wheelbarrow, and shovel. You’ll want to fill the entire footprint of the driveway with a layer of 80 mm (3 inch) crushed gravel that is approximately 100 mm (4 inches) thick.

Once its all laid out, you’ll need to compact it. You’ll probably want to rent a flat plate vibratory tamper for this step. Before you start compacting, make sure you evenly add some water to the gravel. Most gravel requires a bit of water to help proper compaction.

The density of the gravel can increase when you are near the optimum water content of your gravel. (if you’re interested, check out our article on why water helps you during compaction)

But don’t go too wild with the hose – too much water will also prevent your gravel from densifying.

Once you’ve got that first base layer completed – give it a quick raking (not too hard, just enough to scratch up the surface) and lay down your second layer of base gravel, and repeat.

11. Place and Compact the Surface Gravel Layer

Just like what you did before, lightly scratch the surface of the base gravel layer, and lay down your 20 mm (3/4 inch) crushed gravel evenly across your driveway footprint, slightly higher than your final desired elevation. Try to make the gravel thicker in the middle of the driveway, so it will be easier to make a crown.

Now evenly sprinkle some water over it, and compact it with your vibratory flat plate tamper.

Remember to maintain the crown on the surface of your driveway so that the middle is higher than the edges. This will help it shed water and will improve the lifespan of your driveway (as well as reducing the required maintenance).

12. Maintenance

Step 12 is something nobody wants to do, but it is essential for keeping a gravel road useable. Grading should be completed on a regular basis to keep water and melting snow running away from your gravel surface as quickly as possible.

Ponding water is a road or driveway’s worst enemy. If you can control water, you can control the performance of your road.

Conclusion

We hope that this step by step guide to building a gravel driveway has been helpful. If you need any more help, have any comments, or you’d like us to take a look at your project please send us a note.

FREE GRAVEL DRIVEWAY CONSTRUCTION DRAWINGS