When building something from a new driveway to a new access road, a vehicle parking lot, or even a civil works project, one of the first considerations to make is what type of base material will be best. Gravel and roadbase are two of the most common: on the surface they may seem pretty similar, but once put into place and made to work, they are entirely different. Choosing the wrong material can result in a surface that ruts, shifts, or disintegrates in less than a year.
We transport both gravel and roadbase at Formula Transport for many different applications, from driveways on residential properties to large scale construction projects. In this primer we make clear how gravel differs from roadbase, where it is most useful, and what factors to consider when selecting the best material for your project.
What Is Gravel?
Gravel Gravel is naturally occurring. It is made up of small loose rock fragment and is formed by the weathering and erosion of larger stones. There are different sizes of gravel; from fine (pea gravel) to larger (Crushed rock). It can be sold in washed or unwashed forms.
Due to the often rounded and irregular shape of gravel particles, they do not interlock tightly like angular material do. This provides gravel with a less dense, free-draining material and is the reasons why it is so popular for use in some applications but not others.
Common uses for gravel include:
- Garden paths and landscaping features
- Cosmetic access roads and low speed routes inculdes:
- Drainage layers and French drains
- Backfill of pipes and drainage systems
- A natural looking rural driveway.
What Is Roadbase?
Roadbase is an engineered material manufactured from crushed rock that is heavily graded in particle size by type which may include coarse aggregate down to dust, specifically a wide range of particles sizes-often called DGB (dense graded base or D.G.B.) or crushed rock road base. Roadbase is an interlocking, durable base material which will become tightly packed when compacted with the small particles filling spaces between the larger particles.
It's this level of compression that makes a class 2 road base such an ideal material in those applications that are going to have regular vehicle usage or heavy loads passing over them. Properly compacted, it creates a solid, stable surface that does not slip, rut or wash away in the wind like loose gravel does.
Common uses for roadbase include:
- Driveways which carry automobiles, trucks or trailers
- Sub-base layers beneath Paving (concrete, asphalt)
- Access roads on construction and civil sites
- Car parks and hardstand areas
- Pads and foundations that need a firm footing
Gravel vs Roadbase: Key Differences
The main distinction between gravel and roadbase is the materials' ratio of compaction. Gravel has particles that are similar in size, meaning they tend to roll and sit loosely, and don't leave you feeling very solid when you walk across them-much less when a vehicle drives across them and they are also not readily permeable. Roadbase will contain a mixture of sizes of particles to be compacted into a firm surface.
This directly affects performance. Gravel surfaces will move, scatter and form ruts or potholes as a result of traffic or heavy rain, but this is countered to a degree by the roadbase as the precise packed structure holds the particles together and distributes the load so there is less movement.
Another comparison is drainage. Gravel's lack of cohesion means water filters rapidly through; this can be advantageous in some landscaping and drainage situations but also means erosion may occur on a sloping site. Roadbase will shed surface water, when compacted and graded to the desired fall, but stay in position below.
Maintenance and overall cost will differ: Gravel is generally a cheaper option initially and may be simpler to install but it does need frequent addition of new gravel and occasionally having to be re-levelling as it spreads out and compacts over time. Roadbase is a more expensive option to install (as is generally needs to be compacted with machinery), but is far less maintenance and is much more durable.
Which Material Should You Choose?
The best option will vary according to how you plan to use the finished surface. For a decorative hard landscaped path, a garden no-go or a drainage layer, gravel is an inexpensive, practical solution with the added bonus of being simple to install. If architectural load bearing is an issue, then it is perhaps a less appropriate choice.
For ANY project where there is road traffic, heavy machinery or permanent structure stability is required (driveway, access road, car park, sub-base for concrete or paving), roadbase is almost always the superior choice. Roadbase is an engineered material with composition that is resistant to breakdown under such conditions.
Using both materials together can be advantageous on certain projects. A typical application could be a driveway where the foundation is a firm compacted roadbase, with a decorative layer of gravel on top. This enables you to have the strength of the roadbase beneath, coupled with the attractive gravel finish on top.
Factors to Consider Before You Order
- Traffic and load: Is this for vehicles, machines, or just foot traffic?
- Drainage, slope: Do you want the site itself to drain freely or need a maintained, water tight surface?
- Budget: Gravel tends to have a lower purchase price, but the savings may be less in the longer term as maintenance costs will be lower if roadbase is used.
- Application depth: Roadbase typically has to be laid and compacted in layers.
- Finished look: gravel has a more natural, decorative appearance; roadbase is mostly used beneath a layer of sealing, pavers or asphalt.
Getting the Right Material Delivered
No matter what material you require to achieve your project objectives, having the correct quality and quantity being delivered when you need it will determine the success of your job. Formula Transport uses a large stock of gravel and roadbase and specializes in delivering these materials all over the region, offering multiple grades suitable for residential driveways and landscaping as well as larger commercial or civil projects.
Let our team help determine the best type of material, quantity and delivery schedule for your project. From one truck load of airstone to large full-site deliveries we can handle the delivery so you don't have to worry about it.
Final Thoughts
Both gravel and roadbase have their uses and applications in both landscaping and construction, but they are not interchangeable. Use gravel for decorative purposes, light traffic and situations where good drainage is needed. If you need strength, stability and longevity, use a well-compacted 40mm or 53mm roadbase. Knowing this at the beginning will save time, money and hassle in the long run!
Not sure which material you need for your project? Speak to the team at Formula Transport. We'll be happy to run through your site requirements and arrange for an efficient delivery of the gravel or roadbase you require, exactly when you require it.
FAQs
What is the main difference between gravel and roadbase?
Gravel is comprised of small, equal-sized pieces that can drain readily but not be compacted. Roadbase is an appropriately graded combination of various-sized particles designed for compacting into a densely packed, sturdy, load-bearing area that can tolerate traffic and other loads.
Is roadbase more expensive than gravel?
Roadbase typically presents higher initial costs because of the need for material grading and compaction. Over the long term this is less expensive than gravel as there is very little maintenance; mostly just re-topping up.
Can I use gravel for a driveway?
While not suitable for normal vehicular traffic, Gravel may be suitable for low traffic, remote, or aesthetic driveways. Gravel does not settle evenly under repeated loads so roadbase is the best choice for driveways with cars or trucks.
How deep should roadbase be laid for a driveway?
Roadbase should be laid in layers that have been compacted, over all areas, the depth of these layers should normally be 100150mm, depending on the type of soil and number of vehicles using the surface. Several layers compact more efficiently that one thick base.
Does roadbase need to be compacted?
Yes compression is definitely necessary. Road base will not gain its strength and stability until it has been compacted using a plate compactor or roller. If not compacted it is similar to loose gravel and will not carry loads.
Can gravel and roadbase be used together?
Yes, its usual to do both. Roadbase provides a compacted structural base layer underneath a thin layer of decorative gravel on top. You have durability below with a natural appearance above.
Which material drains better, gravel or roadbase?
Gravel will drain water more freely. By its loosely aggregated structure is ideal as drainage layer. Roadbase by its graded and compaction with correct falls still shed surface water and support as stable bed.
How do I know how much material to order?
Order quantities are determined by the size of the area, the depth needed and the compaction factor. Transport's team will work this out for you to determine the exact volume needed so you do not over order or under order and have to pay for unwanted material.
