Contact will be made with all local utility companies at least 48 hours before excavation to have all public underground utilities located. Although every precaution will be taken, it does not ensure that any shallow buried utility lines will not be interfered with. All private utility and service lines are the sole responsibility of the owner.
Excavation on most residential driveways will be 11-12 inches in depth and 12 inches oversized on all parameters. Any sub-grade materials found and deemed unsuitable or un-compactible shall be removed and replaced with clean compactible backfill material. Such conditions would include saturated soils, organic materials, construction debris, tree roots, and large glacial boulders.
Adequate compaction of the soil sub-grade and aggregate base materials is essential to the long term performance of the pavement.
Due to the many freeze-thaw cycles and the heavy clay soils found in this region, Meadowood recommends the use of a Geo-Textile liner. Geo-Textile is a woven fabric placed between existing sub-soils and aggregate base providing long-term soil separation and stabilization to the base and prevents the upward pumping of silt and other contaminating soil fines into the aggregate. This confining action maintains the thickness and hence the intended load-bearing capacity of the aggregate base, and also reduces localized stress by redistributing traffic loads over a wider sub-grade area. Our practice is to install Geo-Textile on every installation we stand behind.
The most critical and essential element to the long term performance of any paved surface is the base preparation. The thickness of the base is determined by traffic loads, soil strength, sub-grade soil drainage and moisture, and climate. A general base thickness guideline for residential driveways in our region is 8-9 inches; for residential patios and walkways, 4-6 inches.
Gradation of base material may vary slightly due to the availability of materials in your area. Meadowood prefers a 3/4" inch minus crushed limestone (class 2). The gradation and uniformity of the class 2 allows us to install a tightly compacted surface. A tightly-compacted base will not allow the bedding sand to migrate into it. The uniformity of material allows us to easily install a concise and uniform grade. (Variation in the final surface elevations should not exceed +/- 1/4" over ten linear feet.) Special attention is given to the design and layout providing optimum drainage and comfortable transition of grade.
The minimum recommended slope is 1.5 percent, or a drop of 3/16" per foot of pavement (ideal for patio installation). Many pavements are sloped at 2% or 1/4" per foot as this facilitates drainage. The maximum slope for comfortable walking is 7 degrees or about 12%.
Occasionally we install a recycled concrete base material on projects that have older, mature trees that are sensitive to limestone (a high alkaline product). Although structurally sound, recycled concrete does not provide the consistent gradation and uniformity of the class 2 limestone and is only used for specific conditions.
Base material is placed, graded and compacted in 4"-6" lifts. Controlling the moisture content of the base material during this phase of installation is critical to achieving maximum density. The optimum moisture level, approx. 15%, must be obtained while compacting. The correct amount of water is necessary to allow the aggregate particles to slide together. The water, therefore, acts as a lubricant. Too much water will take up the space between the particles and prevent them from bonding together.
Base compaction is completed with a dual drum vibratory roller or a large vibratory plate compactor. Final compaction should be at least 97% of modified proctor density. Compaction moves the aggregate particles, re-arranging them closer to each other, while the air or water trapped between these particles is forced out.
With increased density, the soil or base is better able to support a load without settling or rutting. Inadequate compaction will inevitably fail, slowly separating, settling or rutting the paver surface, decreasing the life of the pavement. Frozen base material should never be compacted nor should material be placed over frozen sub-grade soils.
We use the “Pave Edge” Restraint system to contain the bedding sand and pavers. This prevents separation due to horizontal forces. The Pave Edge system is a below-grade system which allows us the flexibility to accommodate a wide range of contour and design changes. Unlike rigid retaining systems, this system performs well during freeze-thaw cycles by adjusting to the vertical movement of the sub-base material.
When a compacted aggregate base supports the paver and bedding sand, the base should extend beyond the restraint. The rule of thumb is the base should extend beyond the restraint the same dimension as the thickness of the base material. For example, if your driveway has 9 inches of compacted base, the excavation and geo-textile would extend a minimum of 9 inches laterally beyond the paved edge. This contributes stability to the restraint, especially in heavy clay soils subject to heaving. Soil backfill is never a suitable edge restraint, and edge restraints should never be installed on top of the bedding sand.
BEDDING AND JOINT SAND
Coarse washed sand is the only acceptable sand used for paver applications. The sand should be sharp and have syaCoarse washed sand is the only acceptable sand used for paver applications. The sand should be sharp and have symmetrical particles, clean of mud and foreign particles. Do not use mason or silica sand. Both are too fine and will not aid in the horizontal and vertical interlock of the pavers. Too fine a joint sand will wash out while too fine of bedding sand will slow the drainage of water and cause the pavement to rut and settle unevenly. Do not screed or lay pavers over sand that has been saturated by rain.
Bedding sand is spread and screeded to a consistent thickness using one inch outer diameter screed pipes. Bedding sand should be placed for screeding on a compacted, even base surface. The bedding sand should not be used to fill depressions in the contour of the compacted base. The filled depressions will be reflected in the surface of the pavers over time creating a washboard appearance.mmetrical particles, clean of mud and foreign particles. Do not use mason or silica sand. Both are too fine and will not aid in the horizontal and vertical interlock of the pavers. Too fine a joint sand will wash out while too fine of bedding sand will slow the drainage of water and cause the pavement to rut and settle unevenly. Do not screed or lay pavers over sand that has been saturated by rain. Bedding sand is spread and screeded to a consistent thickness using one inch outer diameter screed pipes. Bedding sand should be placed for screeding on a compacted, even base surface. The bedding sand should not be used to fill depressions in the contour of the compacted base. The filled depressions will be reflected in the surface of the pavers over time creating a washboard appearance.
PLACEMENT OF THE PAVERS
Contrary to popular opinion, this aspect of installation, while still very technical, is one of the faster procedures in completing interlocking pavements. When the proper techniques have been utilized in terms of excavation, compaction of base, final grade, and screeding sand, on average, a well-trained crew of four craftsmen will complete 800-1000 square feet of pavement per day.
When placing the pavers on the sand bedding there are three key factors in achieving a professionally installed pavement. It is essential these details are not overlooked before cutting in the soldier course and completing the final step of compaction.
First, it is critical the color blend maintains an even consistency. When pavers are manufactured they are blended within the pallet, therefore it is very important to work off of 2 or more pallets at a time on the laying edge. At Meadowood it is common to custom blend and often we install from up to 6-8 pallets at a time. Good communication between the installer and the men tending the laying edge will furnish a well-balanced blend.
Second, the bond lines must be kept straight. On most jobs string or chalk lines are laid to keep the lines of the paver joints running straight. A chalk line is snapped on the screeded sand in the center of the area to be placed, or every 10' -15'. Pavers are then laid on both sides of the line. The line should be perpendicular to a starting line or edge restraint. Great care is taken in this phase to ensure an esthetically-pleasing pavement.
Finally, the pavers must not be overly depressed, or prematurely compacted before the pavement is secured and ready for vibration. It is very important to keep unnecessary traffic off the unsecured pavement and all foreign debris from the surface and joints. If the pavers become depressed or tipped in heavy traffic areas, they must be removed and the sand bedding replaced. A straight edge or string line will show any dips or potential inconsistencies in the surface.
Once the pavement has been placed, the lines have been straightened, and the surface has been cleared of any debris, we are ready to cut in the soldier course and secure the pavement with edge restraints where necessary. At Meadowood, great care is taken with layout and design. The layout and soldier course should be carefully discussed prior to installation to highlight the culture of the pavement and site. For these reasons tremendous effort is put into symmetrical cutting and pristine design layout. We understand that the most important aspect of the life of the pavement is the unseen structure underneath the surface. Yet, the most important aspects to our clients are the visible performance and, of course, an esthetically-pleasing pavement.
The pavement is now ready for the final compaction. The objective is to compact the pavers into the bedding sand with a vibratory plate tamper, and create an interlock that will spread pedestrian and vehicular loads. The purpose of the initial pass is to compact the sand and have it rise up slightly into the joints between the pavers at the bottom. When this is complete, and before spreading sand on the surface, we carefully inspect the pavement for any blemished pavers and remove them. Once the sand is spread and compacted, the pavement locks up and it is very difficult to remove single pavers.
Two to three passes with the tamper are recommended to completely joint the pavers. Before each pass, dry, coarse sand should be swept across the surface. Wet sand does not sweep or vibrate easily into joints. If the sand is wet, it is swept on the pavement and left to dry. We repeat this process until the joints are full and sand can no longer be vibrated down into the joints. If working conditions permit, it is common to spread the sand and vibrate simultaneously. When the joints are completely filled, we remove excess sand from the surface and the pavement is instantly complete.