Best Base for Concrete Driveway: Comprehensive Guide

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What Is the Best Base for Concrete Driveway?

The best base for concrete driveway should be a complete “soil support system” that consists of the subgrade, the sub-base and the base. This will ensure stability & durability.

Subgrade is compacted topsoil. Sub-base is layers of crushed stone or angular gravel, graded such that the largest pieces are at the bottom. Each layer must be compacted. The base is a layer of pea gravel topped with a layer of coarse sand. Once again each layer must be compacted or tamped.

Two products often missed while preparing the best base for concrete driveway are geotextile fabric and vapor barrier (aka vapor retarder). However, both should be incorporated as they play a very important role.

The cross section off a high quality concrete driveway should have the following layers, top to bottom:

#	LAYERS
#1	Topical Sealer will ensure that rainwater or snowmelt does not penetrate into the concrete driveway.
#2	4” – 6” of concrete reinforced with rebar, wire mesh or fibers (depending on concrete thickness)
#3	Vapor Retarder is not required by code but incorporating it prevents ground moisture from permeating into the concrete. Moisture penetration is extremely damaging to concrete
#4	2” of Base made up of a layer of pea gravel topped by a layer of coarse sand. Each layer must be tamped or compacted.
#5	4” – 6” of Sub-base made up of several layers of crushed stone or angular gravel.  The size of the crushed stone or angular gravel must increase from top to bottom. The largest pieces must form the bottom most layer. This will provide structural strength. Each layer must be compacted.
#6	Geotextile prevents the migration of crushed stone or gravel from the sub-base into the subgrade under hydrostatic or seismic stress while allowing downward migration of rainwater for good drainage.
#7	Subgrade which is native soil tamped to a firm finish.  In case the quality of the existing grade is not satisfactory, use a couple of inches of good quality top soil to improve the quality of the subgrade.  Quality of the subgrade can also be improved by treating it with cement or lime.

RECOMMENDED PRODUCT

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The Best Geotextile Driveway Fabric for Your Driveway & Patio Base

Geotextile driveway fabric is a supportive layer that is laid between the compacted subgrade and the sub-base aggregates to prevent the migration and loss of the aggregates in to the subgrade. It helps stabilize the ground, permit drainage and prevent weed growth.

Here is the Geotextile Driveway Fabric I recommend.

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What Is the Best Base Material for a Concrete Driveway?

The best material for a sub-base or a base should:

• Be Inert & Free of Foreign Matter
• Have High Strength & Durability
• Should lack Cleavage Planes to Avoid Splitting
• Be Tough & Abrasion Resistant
• Have Random Angular Profile & Texture to Facilitate Interlocking
• Be Low in Moisture Content

Some commonly used options are crushed stone and angular gravel. Angular gravel is found in natural environments such as river or lake beds. 

Crushed stone, on the other hand, is processed by breaking larger stones, such as limestone and grading it by size. Crushed stone has sharper edges than gravel. 

Both gravel and crushed stone have a number associated with it which indicates the average size of individual pieces. As an example, the average size of individual pieces in #1 will be 2” – 4” while that in #5 will be around 1“.

Some of the specialty grades used as sub-base and base material for concrete driveways are:

# 57  – The stones or gravel are around ¾ “ long. This grade is considered among the best aggregate sizes for use in sub-base of concrete driveways and roads.

# 67 – The stones or gravel are around ¾ “ and smaller. This grade is considered as a great material for road and slab base as well as fill.

# 8 – The stones or gravel are around ¼ “ to ½ “ in size and are often referred to as pea sized. This grade can be used as the topmost layer of the sub-base or the bottom most layer of the base.

# 10 – The stones or gravel are  ⅛ “ or smaller and are also called screenings. This grade can be used as the topmost layer of the base as an alternative to or along with coarse sand.

So crushed stone and gravel are excellent for use as a sub-base and base under a concrete driveway. A range of grades (sizes) have to be used in layers. Each layer must be compacted before the next layer comes on.

Crushed stone or gravel can also be substituted by Recycled Concrete (RC), which is both Eco Friendly & Economical.

Bottom Line

The bottom line is that the best base for a concrete driveway must be a complete soil support system consisting of subgrade, sub-base and base. Do incorporate a Geotextile Fabric and a Vapor Retarder. Further it must use the best material for each layer that is compacted.

Thank you very much for reading this post. I do hope you found it informative and helpful.