Frequently Asked Questions
  1. What are Calstone Interlocking Concrete Paving Stones (Pavers)?
  2. How do the pavers interlock?
  3. Can I use these pavers for my driveway?
  4. Would it be better to mortar the pavers into place?
  5. What type of sand do I need to use between my pavers?
  6. What type of sand do I need to use under my pavers?
  7. Does the water drain through the sand around the pavers?
  8. Can I lay pavers over my existing asphalt or concrete?
  9. How do I cut the pavers?
  10. Are Paving Stones Slippery?
  11. Do I need to seal my Calstone pavers?
  12. Will weeds or grass grow in the joints?
  13. What is that white stuff on my pavers?
  1. What are Calstone Interlocking Concrete Paving Stones (Pavers)?

    Calstone pavers are individual precast concrete units. They are manufactured with our state of the art paving stone machine located in San Martin California. This specialized manufacturing process ensures an exacting quality controlled environment that produces pavers of higher strength and durability than normal concrete. Per industry specifications, pavers must meet a minimum average compressive strength of 8,000 psi. This can be compared to a range of about 1,500 - 2,500 psi for poured in place concrete. That means a Calstone paver is 3 times stronger than your current concrete driveway or patio.

  2. How do the pavers interlock?

    Regardless of which Calstone paver shape, color or laying pattern you choose, they are ALL interlocking paving stones. The term "interlock" comes from the friction of joint sand between paver to paver. This interlock provides pavement superiority in a multitude of ways. The pavers distribute traffic loading over a greater surface. The pavers remain flexible and can withstand minor and major movements of the native soils. Maintenance and repairs (if required) are simplified because no mortar is used in the installation process.

    The basic system works like this: The pavers are placed on one inch of bedding sand over a compacted aggregate base. The thickness of the base will vary depending on its application. Pavers and sand are retained using edge restraints. Commonly used edge restraints include concrete curbing, plastic edge restraints, aluminum edge restraints, and concrete edge bond beams. The pavers are compacted into the bedding sand using a vibratory plate compactor. Sand is then swept and compacted into the joints, filling them and creating "interlock".

    Upon completion of this compaction process, the area is ready for immediate use. Unlike asphalt and concrete, no curing time is required for interlocking concrete paving stones.

  3. Can I use these pavers for my driveway?

    Yes! Calstone pavers can be used for ANY type of paving project. Throughout the world. Concrete paving stones are used in airports, streets, driveways, industrial yards, pool decks, anywhere you want to use them. However, pavers are only superior if the system underneath them doesn't fail. This is why we recommend a minimum of 6" - 8" thickness of compacted aggregate base in residential vehicular traffic. If improper materials are used or compaction is not achieved, the base may fail causing the pavers to settle or rut.

  4. Would it be better to mortar the pavers into place?

    No. Setting the pavers in wet mortar or concrete will eliminate the flexibility and superiority of sand set installation and will prevent interlock. It is recommended that you use course angular sand as the bedding course, and a slightly finer angular sand as the joint sand.

  5. What type of sand do I need to use between my pavers?

    Use a angular washed sand with multi-sized grains (approximately 20 - 30 mesh). This angular sand will bind together during the compaction process. A problem with using very fine sand, even though it will fill the joints easier, it will also wash out easier causing a failure in interlock.

  6. What type of sand do I need to use under my pavers?

    Use a course, hard, angular washed sand. This is commonly called "washed concrete sand". This type of sand will not deteriorate over time and will drain water well. DO NOT use stone dusts, limestone screenings, loam, rounded or fine sands.

  7. Does the water drain through the sand around the pavers?

    No. pavers and the joints are not permeable. Water will seep into the joint sand gradually, but once the joint is saturated, water will shed off the paver surface just like any other pavement. Slope (or fall) needs to be designed into your paver project for water to run off naturally. A minimum of 1 inch fall every 8 to 12 feet of paving, away from your home, is recommended. This slope should be designed into your base course prior to installing the pavers.

  8. Can I lay pavers over my existing asphalt or concrete?

    In a simple answer, Yes, you can (but under certain criteria). If the condition of the existing pavement is in poor state (major cracks, heaving, settling, potholes, etc.) it may be a better solution to start over and build the base system up properly. Also, do you have enough threshold clearance to accept a 2 3/8" thick paver plus the 1" sand bedding course? (a total of almost 3 ½") Another consideration is how will you adjoin the pavers to meet other existing pavements? (garage surfaces, sidewalks, etc.)

    If you find your existing pavement meets these conditions, follow the normal installation methods, with a couple additions:

    • Add a woven geotextile fabric over the existing pavement and under the sand bedding course. This will protect the sand from migrating into existing/future cracks and failures of the previous pavement.
    • Use an adequate edge restraint to hold the pavers and sand bedding course (this may require addition construction outside the area of existing pavement).
    • Remove enough of the existing pavement to allow the pavers to gradually taper down to adjoining surfaces. Also excavate enough material to allow proper thickness and compaction of base material to support anticipated traffic.
  9. How do I cut the pavers?

    The two basic methods for cutting pavers are either with a diamond saw blade or mechanical paver splitter. Because of their high strength, pavers are hard to cut. A paver splitter, with a little practice, will make a nice cut but cannot make smaller precision pieces. For more precision cuts and difficult pieces around down spouts, drains, utility boxes, etc., a brick saw using a wet diamond blade is recommended.

    Important note: If wet cutting, be careful to not drip or spray the contaminated water onto the pavers. This type of staining is extremely, if not impossible to remove. Pavers should be rinsed thoroughly before placing them into the laying field.

  10. Are Paving Stones Slippery?

    No. In fact, Calstone paving stones exceed the CalTrans standards for friction coefficient (slip and skid resistance) for freeways and highway construction. Pavers also surpass the slip resistance standards established by the American Disabilities Act.

    Important note: Some sealers on the market can decrease the friction coefficient under wet conditions. Calstone recommends Aldon Penetrating Paver Sealer if you decide to seal your paving stone project. This sealer does not effect the slip resistance.

  11. Do I need to seal my Calstone pavers?

    No, sealing is just an option. But sealing the pavers does have some advantages. Sealing your pavers will:

    • Make clean up of oil, food, or vegetation stains easier.
    • Help stabilize the joint sand from being washed out by rains or heavy cleanings.
    • Help prevent efflorescence from occurring or recurring.
    • Help prevent vegetation growth.
    • Darken and brighten the color pigments in your pavers.

    Sealing your pavers can take place immediately upon completion of installation or at anytime in the future provided the pavers are clean and weather permitting. The area to be sealed should be cleaned and allowed to thoroughly dry (approximately 3 - 5 days of warm weather) before the application of the sealer can take place. Although pavers may appear dry on the surface, it is very important to wait the prescribed drying time before the application of the sealer.

    Calstone recommends 1 - 2 coats of Aldon Penetrating Paver Sealer. This is a solvent based sealer and will outlast and out perform most water based sealers on the market.

  12. Will weeds or grass grow in the joints?

    If the pavers were installed properly, with the recommended materials and installation methods, you have created a sterile environment to allow weeds to grow "through" the pavers. There will still be times when seeds can blow into the top of the joints and start growing in any organic material that has built up in the joints. If this happens, you can normally pull them out very easily or remove them with a topical weed killer spray.

  13. What is that white stuff on my pavers?

    Occasionally, some pavers may have a whitish residue upon them. The whitish colored residue is called efflorescence. Efflorescence is a natural by-product from the cement hydration process and can be found in any concrete or mortar product.

    Calcium oxide inside the paver reacts with water in the capillaries and forms calcium hydroxide. This seeps to the surface, and reacts with the carbon dioxide in the air to form calcium carbonate, a whitish residue. When moisture on the surface evaporates, the white efflorescence becomes visible.

    If efflorescence is present, it will wear off over the course of time with traffic and the elements. If you wish to speed up the removal of efflorescence, Calstone recommends the Aldon Paver Restore.