Are you thinking about having your driveway paved? The following information will outline the basic conditions required for your driveway to “hold the road” for more than 20 years.
Remember first that, in addition to the techniques and weather conditions necessary for applying the materials, the main indicators of an asphalt surface’s durability are:
- the quality of the granular base;
- the thickness of the asphalt layers;
- the efficiency of surface drainage.
Laying the granular base
- Whether for a new or rebuilt driveway, any asphalt surface must first be dug up to lay a fresh bed of crushed stone of a thickness that suits existing ground conditions.
- For optimal stability, this granular base should exceed the width of the surface to be paved by at least 12 inches (30 cm) on each side.
- The recommended depth of excavation is 12 to 18 inches (30 to 45 cm) for sandy soil and 18 inches (45 cm) or more for poorly drained clay soil.
- When the house is new, you have to wait for the earth to settle naturally, a period of six to 12 months, before undertaking paving work.
- Clay soil should be covered with a geotextile membrane to prevent the rise of soil particles that are likely to affect the stability of the granular mixture.
- The granular mixture must meet the MG-20 metric designation. This refers to granulate made up of crushed stones of a maximum size of 3/4 of an inch (20 mm) across. The fill must be adequately compacted in two layers when more than 12 inches (30 cm) thick.
- Lack of compacting and inadequate thickness of the granular foundation are the most common causes of the asphalt layer buckling or cracking.
Conditions for efficient runoff
- The asphalt layer must have a minimum 2% incline, or 1/4 inch (6.5 mm) per foot (30 cm), to allow water to flow to the street and to avoid water infiltration that could cause heaving or cracking at times of freezing or thawing.
- This incline should ideally be created starting with the excavation and should be maintained during the filling process.
- For parking areas with large surfaces or low inclines, the centre of the driveway should be raised slightly in relation to the sides.
(Illustration: Bitume Québec, available in French only)
Spreading the asphalt layers (paving)
- Asphalt intended for residential use generally consists of about 94% granulate and 6% tar. It is commonly called EB-10 (referring to the 10 mm granulate it contains).
- Coatings with harder surfaces are preferable for regular or extended parking of a heavy vehicle such as a truck or RV: asphalt consisting of a larger granulate (with a rougher and paler finish) or grade PG 64-28 bitumen (instead of PG 58-28, used more commonly in residential settings).
- A layer of asphalt should initially be 2.5 to 3 inches (60 to 75 mm) thick to have a minimum thickness of 2 inches (50 mm) in all places after compacting.
- Installing lateral supports (blocks or curbs) at the perimeter of the coating helps avoid deterioration through cracking.
- Paving done in cold weather will be of inferior quality (with the greater difficulty in compacting leading to a porous finish subject to water infiltration).
A paving contract should specify:
- the contractor’s name and address;
- the Office de la protection du consommateur (OPC) permit number if you are dealing with a door-to-door salesperson; in such cases, never agree to have the work done before expiry of the 10-day cancellation (or resolution) period, to avoid any source of conflict;
- the contractor’s proof of liability insurance (insurance company and policy number);
- the dates the work is to begin and end (the OPC advises including the following sentence in the contract: “The work will be completed no later than (date), or the contractor agrees to refund the deposit.”);
- the exact dimensions of the surface to be paved;
- the depth of excavation, whether a geotextile will be used, the type of fill and asphalt, and their thickness after compacting;
- specification of all extra items (e.g., moving a fence, installing a grid on the driveway drain, etc.);
- the terms and duration of the warranty provided;
- total cost and terms of payment;
- that the presence of puddles (resulting from a poor drainage incline or settling of the asphalt) will not be tolerated;
- that the contractor will keep the site reasonably clean and will dispose of the debris and excavation material in keeping with work completion standards.
Please note: A contractor should never require a down payment for this type of work.
Sources: Bitume Québec and OPC