Adjusting manhole frames after a paving project is a task that calls for precision and care, often relying on specialized saws designed for road maintenance to achieve clean edges and proper alignment. When done right, it preserves the integrity of the new surface and ensures long lasting utility access. Whether you are a site superintendent, contractor, or maintenance worker, knowing how to raise or lower manhole frames without hurting the new asphalt is a valuable skill.
Properly adjusting a manhole frame might seem straightforward, but there are pitfalls that can lead to cracks, settlement, or future maintenance headaches if not handled correctly. This article will guide you through the steps, tools, and best practices to get the job done smoothly.
Why Adjusting Manhole Frames Matters
Adjusting manhole frames correctly after repaving protects the investment you have made in a new surface. It also ensures a safe, level experience for vehicles and pedestrians using the area.
In many repaving projects, the final asphalt thickness ends up above or below the existing manhole frame. Without making adjustments, the frame could end up too low, creating a bump or tripping hazard, or too high, causing premature wear and damage from traffic.
The Challenge of Fresh Asphalt
Fresh asphalt is vulnerable, especially in the hours and days after it is laid. Excessive force, improper supports, or careless lifting can crack or deform the surface, setting back your project timeline and raising repair costs.
Tools and Materials You Will Need
Before you begin any adjustment, gather the right tools. Being prepared reduces the chances of mistakes and damage. First, ensure you have a solid work plan and proper support from your crew. Work zones should be cordoned off to prevent accidental traffic on the fresh pavement.
The tools you will typically need include:
Adjustable wrench or socket set for frame bolts
- Pry bars and lifting keys
- Shims or leveling rings of appropriate thickness
- A straightedge to check level with the surrounding pavement
- A small jack or lifting mechanism designed for manhole frames
Step by Step: How to Raise a Manhole Frame
Raising a manhole frame after repaving requires gentle handling and careful measurement.
Assess the Frame Height After Paving
Once the asphalt has cooled and hardened, inspect the frame height relative to the surface. You want the top of the frame to be flush with the finished pavement.
Remove Debris
Clear any loose stones, asphalt crumbs, or dirt from around the frame and inside the frame channel. This helps ensure a smooth adjustment.
Loosen Frame Bolts Slowly
Use your wrench or socket set to gradually loosen the bolts that secure the frame to its base. Do this slowly so the frame does not suddenly shift.
Use the Lifting Key to Raise the Frame
A lifting key or frame lifter provides controlled lifting force. Lift the frame just enough to insert level rings or shims beneath it. Work slowly and keep checking with your straightedge to match the pavement surface.
Insert Shims or Leveling Rings
Place the appropriate number of shims or rings to reach the desired height. These components create a new support plane between the frame and the original structure below.
Secure the Frame
Tighten bolts gently but firmly after checks confirm a flush height. Ensure there is no wobble or gap between the frame and the new support pieces.
How to Lower a Manhole Frame
Lowering a frame is similar but requires you to remove material instead of adding spacer rings.
Measure the Amount to Lower
Compare the frame top to the surface. A reliable straightedge helps ensure your measurements are accurate.
Loosen Hardware and Lift Slightly
Loosen the bolts and use a lifting key just enough to relieve pressure. This allows safe removal of material below.
Remove Excess Material
Carefully extract old shims or leveling rings until the frame sits at the desired level.
Check and Reinstall
Once the height matches the surface, re tighten the hardware. Double check that the frame is stable and level.
Best Practices to Avoid Asphalt Damage
Protecting the fresh asphalt is your priority during any adjustment.
- Make adjustments only after the asphalt has cooled sufficiently. Warm asphalt is easier to deform.
- Work slowly and deliberately. Sudden movements can create surface cracks or indentations.
- Keep heavy tools and machinery off new pavement until it has cured fully.
- If the frame needs to be moved immediately after paving, use protective boards or sheets to distribute weight.
Fun fact: Manhole covers were first used in ancient Rome. The design of circular covers stopped them from falling into the opening.
When to Call in a Specialist
Even with the best planning, some adjustments might be better left to experts. Complex sites, heavily trafficked roads, or deeper structures may require specialized equipment or techniques. Certified professionals bring experience that can save time and prevent costly errors.
Raising or lowering manhole frames after repaving does not need to be stressful. By planning ahead, using the right tools, and following careful procedures, you can preserve the new asphalt and achieve a smooth, level finish. Patience and precision are your allies in these adjustments. When done right, the result is a seamless surface that stands up to traffic and time.