Do's and Don'ts of Paver Installation: Base Preparation 2/3

It is now time to get your project started.  Preparing a proper base is crucial for any paving stone project; again, you can refer to Unilock’s technical guide as well as take into account the following pieces of advice to ensure the pavers are being placed on a substantial base:

Don’t cut corners. Now that you have decided on the size of the job and its design you can start with the excavation. Make sure that all phone and gas lines have been marked. You also must over excavate the perimeter of the area.  What I mean by this is, if your patio is 20 feet by 10 feet you need to extend your base preparation past the finished size. The rule of thumb for over preparation is that the base material should extend past the paved edge an equal distance of the base depth.   In other words, if your area is a 10 foot by 20 foot area and you are installing 6 inches of granular material as a base then you must excavate an area 11 feet (10’ + 6” + 6”) by 21 feet  (20’ + 6”+ 6”).

Don’t guess at how much base material is required. A few comments on depth of base materials is necessary since there is no absolute rule to determine depth.  First, local soil conditions impact depth and second, if it is a walkway or a driveway the guidelines are 4 to 6 inches for pedestrian walks and 8 to 12 inches for driveways. Consult your local dealer for further guidance.  Generally clay bases need to be dug deeper to facilitate drainage.      

Do not place plastic under any paving application with the intention of preventing weed growth. In most cases seeds start from the top of the cracks and work their roots down.  Plastic will entrap water potentially causing problems. The best way to prevent weeds is to use a good polymeric sand and ensure that it has filled joints to within 3 mm (1/8 inch) of the surface. If you are in an area that is all clay or other type of poor draining material, it is good practice to place a layer of geo-textile down first then place your granular base.  This will work as a mechanical barrier to stabilize and stop the clay from mixing with your good sub base materials.

Do not dump your base materials in, fill it up and then run your compactor over it.  Most traditional plate compactors will not compact any more than 4” of base.  If you try to compact 6” of base you will only compact the top 4” and the bottom 2” will settle in the future, therefore you must compact your base in layers of 3"-4". If your base materials are dry don’t be afraid to add a little water as this will help with the compaction, and cut down on the dust.

Do take your time. You want the base to reflect all of your finish grades so that when you get to the levelling course you will have a nice, thick, consistent layer of sand. The more time you spend on the base the easier the rest of the project will go. A slope of 1% to 2% is adequate when setting the slope for drainage. It can sometimes be difficult to get an accurate read on slope if you are using a 4 foot level.  A nice trick to help set slope for drainage when you are using a 4 foot level is to tape a spacer under one end of the level and when you read it, level it, this actually means you have your slope. For an example, to achieve a 1% slope you need a ½” fall in 4 feet. Tape a ½” spacer on one end and when the bubble is centered you have your slope. 

Do not compact the bedding sand. This is the most common mistake.  When you do the final compaction the loose sand will be forced up between the pavers and this will set and secure them. Additionally, there is no such thing as 100% height control in any concrete product. The loose sand will allow the tamping process to even out the top surface of the pavers. It is also important to use the correct sand.  Avoid stone dust or limestone screenings as these types of materials usually have too many fines (dust) which will entrap water that can cause early failure of the pavers.  Lastly, only prepare as much area with the bedding course as you can lay the pavers on that day or you may have to re-level the whole area due to unexpected rain or people walking on the area. 

By following the above instructions, the proper base will support the pavers and ensure long lasting quality of your project.  These steps will help prepare you for next week’s blog content; executing the plan and the installation of your paving stones!