What is the difference between paving stones and concrete?
Paving stones are made up of cement, sand, and aggregate similar to concrete. Paving stones due to the compression in the manufacturing process 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 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 reoccurring vehicular traffic would be installed similar to patios and walk ways except for a couple differences. The main difference would be the amount of gravel used . driveways require at least 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 wont grow from the soil all the way up through the paver joints. The most common issue is normally weeds growing in the sand joint only. Over time from walking, driving, and wind, rain, birds, etc., dirt and seeds will make there way into the sand joint and cause weed growth. There are some things you can do to prevent or maintain this. Maintaining would consist of using weed spray or boiling water to kill then remove the plant. Another option would be to simply pull the weeds out as needed. There are some anti fungal sealers than can be applied to prevent any growth and protect your stones. Polymeric sand is also an option. This is a special sand that uses polymers to that bind the sand to prevent weed growth while also preventing the sand from washing out of the joints.
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 there are unforeseen settling that can occur below the sub base. This is very rare but can normally be easily repaired by removing the stones and repairing the sub-base.
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 not 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. Since 2010 the industr y seems to be stabilizing and many of the “fly by night” contractors were “weeded out”. Now to answer the question. 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 always a factor. Its always 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, it probably is. 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. 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. You should never feel pressure to commit to any contractor. if you feel pressured to commit to the job by a contractor this is not a good sign. This tactic is common when trying to charge mo re than fair/normal amounts for work performed. My rule of thumb for any type of substantial financial investment would be to take at least a day to process the information so you can make the best decision. Check that each contractor bidding is specking the correct type of materials and amounts of materials. This insures bid accuracy when comparing and also that the installation process will be performed correctly. Customers are typically most dissatisfied when something is promised during the estimated process and wasn’t delivered or performed during the installation. Make sure you have everything in writing as far as what type of materials and exactly what work will be performed. One common issue I came across frequently while working at the manufacturer was when a contractor promised something and didn’t deliver or wasn’t exactly what had been explained when selling the work.
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 normally 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. You also use smaller size crushed rock in the joints instead of sand.