FACTS AND QUESTIONS
Q. Does asphalt need a base? What should the base be made of?
A. Just as a building needs a strong foundation, asphalt needs a strong base. The base acts as a support, and without good support the asphalt will be prone to cracking and breaking. The base should be even and solid, and compacted so it does not shift under weight. You cannot pave over a loose surface as this will cause the top layer to crack.
One of the more common bases is limerock (also known as limestone, a strong sedimentary rock). The base will be a lot thicker than the asphalt above it – bases of 6 inches or more are common. The asphalt is only a covering layer.
All residential, commercial and D.O.T. jobs require the use of a primer. This helps the asphalt adhere to the base and prevents it breaking or cracking.
Q. How thick is the asphalt layer?
A. The thickness will vary depending on the amount of expected traffic. Normally, it is less than 2 inches thick. Parking lots are normally up to one and a half inches thick, for example. The thickness of the asphalt layer determines the size and weight of roller that needs to be used for compaction – the thicker the asphalt is, the bigger the roller needs to be. As a newly installed asphalt layer cools, it needs to be rolled several times to ensure a smooth compacted surface.
Q. How do you measure the thickness of asphalt?
A. Asphalt is measured after it has been laid and compacted. Compaction is an important part of the process, and by its very nature reduces the thickness of the asphalt layer. Taking the measurement prior to compaction will not account for any settling or rolling.
Q. Is it possible to resurface or overlay asphalt?
A. To keep a road or parking lot surface in good order, it may need to be overlaid from time to time. The usual thickness for overlaying is 1 inch, but the underlying surface must be made good and prepared first. If the existing layer is too badly cracked, it must be removed before attempting an overlay to prevent cracking in the new surface.
If you are repairing existing asphalt, you don’t need a permit to carry out the work – however, if it is a new installation, you will need a permit. This applies to both road and parking areas.
Q. Does new asphalt last a long time?
A. New asphalt can last between 15 to 20 years, and can then be overlaid in order to look new again. If the asphalt is sealcoated regularly, this can be extended by another 5 to 10 years. New asphalt should be left at least a year before sealcoating, and then treated every 2 to 3 years.
Sealing before this time will have a negative effect on the asphalt as it will not have had time to cure fully, but sealing at the appropriate time will help maintain the quality and color of the surface.
Sealcoating helps to protect asphalt from the elements (which can cause oxidization), as well as from damage that can be caused by gasoline and oil.
Q. Are there different kinds of asphalt?
A. While the top surface may appear identical, the actual mix used within the asphalt will vary greatly. As with the requirements for determining the thickness, the usage of the surface must be taken into account when selecting the appropriate mix.
Q. What are the timescales involved?
A. The amount of time required will vary depending on how much preparation is needed and the size of the area. Once the asphalt has been laid, it should be left overnight before use. Attempting to use it immediately may damage the top surface and require repair work to be carried out.
Q. Are we required to have Handicap parking stalls?
A. There are legal requirements specifying the percentage of handicap stalls needed. For smaller parking lots, at least 1 handicap stall for every 25 stalls is required, with the percentage changing as the total number of spaces increase. If you currently have “deeded parking”, you are not bound by these requirements.
Q. What can I do to check I am hiring a good contractor?
A. Check out the history of your contractor by asking references and details of past clients. The county lease board will give you information on the business regarding compliance. Never choose a contractor that does not have current and valid insurance. The best contractors always offer a warranty.