What is the difference between paving stones and concrete?
Paving stones are made up of cement, sand, and aggregate similar to concrete. However due to the compression in the manufacturing process, paving stones are much stronger than standard concrete. Standard PSI (pound per square inch it can withstand before breaking) minimum for a paving stone is 8000, poured concrete is typically a minimum of 3500. Water absorption is also much less for paving stones versus concrete. This keeps the paving stone from chipping and cracking like concrete eventually does. Paving stones being individual units with sand joints also makes a difference by allowing natural expansion and contraction that is usually harmful to concrete.
What is the correct way to install paving stones?
A basic installation guide would be:
- Excavate (not always but in most cases)
- Install crushed gravel
- Compact gravel
- Screed no more than 1” of sand (or less than ½”)
- Lay pavers
- Cut where needed and set edge restraint
- Compact pavers
- Sweep sand in the joints
- Compact and re apply sand until joints are full.
A more specific Installation guideline is based on the use of the area that will be paved.
Patios and walkways: typically some sort of excavation is required to allow for the sub base and stone. Normally you need about 6-7” of excavation for 3-4” of crushed gravel (3/4 or 5/8 minus), 1” of washed sand, and 2 3/8” for the paver itself. Some cases require the walkway or patio to be raised. This application normally doesn’t require any excavation except for the block used around the perimeter to elevate to area. With raised areas most edges that would require edge restraint would instead have paver adhesive applied to the border stand and block used to elevate the area.
Any area with recurring vehicular traffic would be installed similarly to patios and walkways except for a couple of differences. The main difference being the amount of gravel used. Driveways require a minimum of 6”-8” of crushed gravel, up to 10"-12” depending on the circumstance. Geo fabric installation under the gravel isn’t required but is an inexpensive way to strengthen your sub-base.
Will weeds grow through the joints of my pavers?
This unfortunately is the most common maintenance challenge with paving stones. While typically weeds won't grow from the soil all the way up through the pavers, weeds can take hold within the sand joint. Over time from walking or driving, wind, rain, birds, etc., dirt and seeds can make there way into the sand joint and eventually weeds can sprout. Fortunately there are several effective ways you can prevent this and maintain your pavers in good condition. There are some anti-fungal sealers than can be applied to prevent any growth and protect your stones. Polymeric sand is another great preventative option. Polymeric sand is a special sand that uses polymers to bind the sand together which helps prevent weed growth while also preventing the sand from washing out of the joints. In the unlikely chance that these preventative measures fail, weed sprays or boiling water can be used to kill the plants before removal or simply pull the weeds out as needed.
Will my paving stone settle over time and cause dips and potholes?
If installation is performed correctly you should not have any issues with settling. However, occasionally unforeseen settling can occur below the sub base. This is very rare but can easily be repaired by removing the affected stones and repairing the sub-base. One of the many benefits that pavers have over concrete!
How do I choose a contractor?
I wish I had a nickel for every time I was asked this question while working at the paving stone manufacturer. I could have retired by now! This industry is constantly changing. In the 90’s when paving stones were getting there start here in the northwest, this wasn’t much of a challenge because so few companies installed paving stones. During this time you were lucky to find a contractor that knew what they were! Then in the early to mid 2000’s everybody decide to jump on board and offer paving stone installation. At this point most contractors weren’t chosen by how much they charged or how well they presented their companies, but rather how soon they could start the project. The demand was so high you were fortunate to find a contractor that wasn’t booked out for months! In 2009 this all changed. After the economy took a huge hit choosing a contractor became all about one thing... price. The least expensive bid became the winner in most cases. After the economy took a huge hit, choosing a contractor became all about one thing...price. The least expensive bid became the winner in most cases. Since 2010 the industry seems to be stabilizing and many of the “fly by night” contractors were “weeded out.” I’ve found that customers who use professional services are typically most satisfied when they choose based on how comfortable they feel with the contractor. Price is also always a factor. Its a good idea to get 3 bids. Since every job is different, having multiple bids gives some perspective on what a fair price actually is. If you have a bid that seems way too low, there's a reason for that. Low bids are normally due to inexperience and could cause the contractor to cut corners or ask for more money in the middle of the project, leading to unforeseen costs. On the other end, you could have a bid that seems like its way too high. Unfortunately there are construction companies that will start with a high price and keep lowering it until you sign the contract. This tactic is common when trying to charge more than fair/normal amounts for work performed. You should never feel pressured to commit to any job offered by a contractor. This insures bid accuracy when comparing contractors and also helps to insure that the installation process will be performed correctly. Customers are typically most dissatisfied when something is promised during the estimating process and wasn’t delivered or performed during the installation. That was a common issue I came across frequently while working at the manufacturer. Check that each contractor bidding is specking the correct type of materials and amounts of materials. This insures bid accuracy when comparing contractors and also helps to insure that the installation process will be performed correctly. Customers are typically most dissatisfied when something is promised during the estimating process and wasn’t delivered or performed during the installation. That was a common issue I came across frequently while working at the manufacturer. Make sure you have everything in writing as far as what type of materials you should receive and exactly what work will be performed."
Are paving stones permeable?
Most paving stones are not permeable. Typically less than 10% of water will make it way through the sand joint and into the soil. For normal paving stone application, water draining through the joints is a common cause of settling. There are however special “permeable” paving stones that are designed to allow 100% of rain water to drain through the joints. The installation process requires crushed open aggregate instead if aggregate with fines so that water can make its way to the soil. Additionally, a smaller sized crushed rock is used in the joints instead of sand.