Measuring the project area accurately in square yards is the vital first step in estimating the asphalt tons required. Carefully measuring the net paving area in square yards is crucial for an accurate asphalt tonnage calculation. Any mistakes made in establishing project dimensions will carry through and compound when computing the total tons required. Here are some proven techniques:
Rectangular Areas Length Times Width
The simplest measurement technique for rectangular areas is multiplying length by width. For rectangular areas, simply measure the length and width in yards and multiply them. The formula is:
Square Yards=Length (yards)×Width (yards)
- Use a surveyor’s measuring wheel to measure overall length and width dimensions. Confirm measurements do not exceed specified area boundaries.
- For non-rectangular shapes, divide into rectangular segments that can each be measured individually and then summed.
- Account for all deductions like corners, islands, retaining walls, and other areas not being paved within the rectangles.
- Double-check all measurements for accuracy and deduct non-paving areas. Those omitted will inflate ton estimates.
Measuring overall rectangle dimensions and excluding deductions provides the most precise rectangular area size.
Grid Methods
Dividing irregularly shaped areas into grids aids in measuring:
- Create a string grid with square segments of known dimensions like 10ft x 10ft.
- Count the full and partial grid squares within the paved area. Partial segments can be pie-shaped.
- Use the known grid square footage to calculate non-rectangular areas. Sum all segments.
- For irregularly shaped areas, divide the area into smaller grids or squares with known dimensions (e.g., 10ft x 10ft). Count the full and partial grid squares within the paved area and use the known grid square footage to calculate the total area.
This allows incrementally measuring curved or odd-shaped sections difficult to quantify otherwise.
Surveyed Drawings
For civil engineering projects, use CAD drawings showing exact paved boundaries:
- Surveyed plans will provide the required area precisely calculated.
- Be sure to use final “issued for construction” drawings, not conceptual plans.
- Field verify drawings match staked dimensions before using area values from plans.
Survey data provides professional measurement but needs on-site validation before reliance.
Aerial Measurement
Measuring area via online aerial views or satellite imagery may be suitable:
- Tools like Google Earth allow polygonal measurement around boundaries.
- Confirm imagery matches current on-site conditions without changes.
- Some distortion occurs in satellite views requiring localized calibration measurements.
Establish Control Points
Use control points like building corners or manholes for fixed on-site references:
- Control points validate distances measured from plans and images.
- They provide fixed starting points for measuring wheels and help orient irregular segments.
Control checks ensure measurement accuracy essential for the subsequent asphalt tonnage calculation.
Important Questions
What method works best for simple rectangular areas?
For rectangles, multiplying the overall length by the width provides the total area.
When are grid techniques most useful for area measurement?
Dividing into measured grid squares aids in quantifying irregularly shaped sections.
What should you verify before using the area shown on project plans?
Confirm the plans reflect current on-site conditions before using the specified area.
Name one disadvantage of relying solely on aerial imagery areas.
Some distortion occurs in aerial imagery requiring localized calibration.
Accurately establishing project dimensions in square yards is a vital foundation for a precise asphalt tonnage estimate. Careful area measurement avoids compounding errors. My 20+ years of estimation experience confirms the importance of correctly quantifying area first.
Determine Asphalt Thickness
Correctly determining the asphalt thickness for a project is another key input in estimating tons. Here are best practices on dialing in proper depth values from my 20+ years of experience:
The asphalt thickness specified for a paving project significantly influences the total tons required. Accurately establishing, documenting, and tracking thickness is crucial for estimating accuracy. Here’s how I determine and validate thickness requirements:
New Construction vs Resurfacing
Thickness selection depends on whether it’s new pavement construction or resurfacing existing:
- New Installations – Parking lots, roads, and other new asphalt construction require full-depth pavement structures over an aggregate base. This involves multiple layers totaling 4-8 inches commonly.
- Resurfacing – Overlaying or resurfacing existing sound asphalt requires less thickness, typically 1-3 inches. Thin applications maintain grades.
Match thickness values to the specific project scope requirements.
Typical Thickness Guidelines
Some general rules of thumb for thickness by usage:
- Parking Lots: 4-6 inches total asphalt thickness
- Driveways: 2-3 inches asphalt over base
- Roadways: 3-4 inch wearing surface over base
- Airport Runways: 10-15 inches or more over base
These provide reasonable starting points. Consult engineered designs.
Engineer’s Asphalt Thickness Design
Follow the recommended asphalt depth designed by registered engineers per traffic loading needs:
- The design report specifies the required asphalt thickness over base materials for structural capacity.
- This professional recommendation provides the authoritative depth value needed for subsequent tonnage calculations.
Deviating from the engineered depth can lead to premature failures or cause inaccuracies in estimating tons.
Verify Against Contract Documents
Always cross-check that construction drawings and specifications match the design report thickness:
- If a discrepancy exists between the designed and contract-required thickness values, seek clarification before paving.
- Using incorrect thickness creates problems during inspections and payment.
Account for Any Field Changes
If depth must be adjusted in the field based on actual subsurface conditions uncovered, document the change order thickness carefully. Revise tonnage calculations accordingly.
Important Questions
What types of projects typically require the thickest asphalt sections?
New airport runways often require the thickest overall asphalt sections due to heavy aircraft loading.
If specifications call for a 4-inch wearing course, what document provides this requirement?
The engineered design report should specify paving layer thickness requirements.
What should be done if subsurface conditions require increasing thickness during construction?
Any field changes increasing asphalt thickness must be carefully documented to update tonnage calculations.
When can using the wrong paving thickness value be problematic?
Using incorrect thickness causes problems during inspections, payment approvals, and future maintenance.
Specifying the proper asphalt depth for the project purpose is imperative for an accurate tons estimate as well as pavement performance. My 20+ years of experience can help validate thickness selection.