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Inspecting and Assessing a Failed Bluestone Patio Installation

A thorough inspection and assessment of a bluestone patio installation ensures longevity, safety, and aesthetic performance. The process involves evaluating site preparation, materials, drainage, stone condition and placement, jointing, edging, structural stability, and maintenance needs. Below is a step-by-step guide for how we inspect a patio for restoration.

1. Subgrade and Base Evaluation

• Visual inspection: We will look for settled or heaved areas, soft spots, or sinking that indicate inadequate compaction or unstable soils. The number one cause for a patio installation to fail is its base.

• Depth verification: We will confirm base depth is consistent with requirements (commonly 4–6 inches of compacted crushed stone for patios, adjusted for soil and frost conditions). When we install a base, we only install open-graded bases, totaling 9” of depth from the surface of the patio. Our techniques are perfectly fitted for our areas wetness, and our hard freezes, typically during our wettest seasons.

• Compaction: Proper compaction should resist driving a screwdriver more than a few inches under moderate force. Proper basing is the most important piece of the puzzle.

• Drainage slope: The subgrade and base need to provide a minimum slope of 1/8"–1/4" per foot (1–2%) away from structures to prevent water pooling near foundations. This step is often overlooked for natural stone patios. The uniqueness of each piece of bluestone make the installation more of an art form. One that we pride ourselves on.

• Geotextile and edge restraints: Verify presence and correct placement of any fabric or edging specified to prevent base migration and lateral movement. We often try to use larger boulders or walls. Whenever the design calls for an opening along the patio, we utilize concrete edge restraints. If an incorrect type of geotextile fabric is installed, it could be pooling water. Geotextile fabric or georgic is not always necessary, but it is recommended.

• If any of these problems are present, We will always recommend a full replacement. Only by removing and replacing the entire base system can we guarantee there will be no hidden problems.

3. Bluestone Material Inspection

• Stone quality: Stone must be inspected for; Consistent thickness tolerance, absence of excessive cracks, seams, or brittle fractures. Natural variations in color and texture are expected. Our full color assortment is our most popular choice, however, we also off “clean” bluestone which will have a more uniform color palette. Please note: Color variations are completely random. if specific colors are desired, this will increase material costs.

• Thickness uniformity: Stones must meet thickness guidelines (commonly 1"–1.5" for veneers on reinforced concrete slabs, 1.5"–3" for loose aggregate bases; larger structural slabs may vary). Significant thickness differences can cause uneven surfaces and instability.

• Flatness and warping: Each stone is checked for excessive bowing or warpage that could cause rocking or tripping. When pieces are mismatched, it becomes impossible to keep consistent grades across long distances. We try to keep our irregular pieces as big as possible, but on pattern bluestone installations the size of the paver should not be smaller than 6”x12”.

4. Stone Placement and Bedding

• Bedding material: We must confirm correct bedding medium (compacted aggregate, or mortar bed as specified). For dry-laid bluestone, a compacted 3/4" crushed stone or sand base is common; however, 95% of the patios we have restored, have a base that includes sand. For our area, sand will hold moisture, allow weed and insect contamination, and will heave in the winter months. Any base consisting of sand as a part of the base, should be replaced. For mortared installations, base should be consistent mortar coverage beneath stones.

• Level and grade: Precision lasers and other equipment are used to verify uniform a plane and that stones meet the intended slope for drainage. Transition areas to walkways, steps, and junctions with structures must be smooth and safe.

• Joint widths and alignment: Check joint widths for consistency with design (We strive for 1/2" joints, depending on aesthetic and jointing method). Irregular or overly wide joints can collect debris and affect stability. Most jointing materials will fail faster with inconsistent joint sizes. When a joint is created, it must be as short as possible. Long running joints will prevent the paving from interlocking, which will add to the chance of failure.

• Stone seating: Each stone should rest evenly on the bedding with full contact—no rocking or voids beneath. Any hollow stones will eventually fail or break. this is common with bluestone installations as the bottoms of the stone are rarely flat.

5. Edge Restraints and Structural Integrity

• Edging: We will verify the presence of installed edge restraints (metal, plastic, poured concrete, or stone curbs) to prevent lateral movement. Edge restraint must be secure and seated in compacted base. We recommend a high strength concrete edge restraint.

• Transitions: We will inspect transitions to steps, lawns, driveways, and other hardscape to ensure proper support and smooth grade changes that eliminate trip hazards. Smooth transitions will not only make the installation safer, but will absolutely add to the ascetics of each project.

• Retaining walls or raised areas: Confirm walls supporting the patio are properly engineered, drained, and capped. Look for signs of movement, cracking, or bulging. Improper drainage will cause a base to hold water, which in turn will increase the chance of failure.

6. Jointing and Pointing

• Joint material: Determine whether joints are filled with sand, polymeric sand, mortar, or left open with plantings. Joint material must suit expected use and local climate (polymeric sand for stability; mortar for rigid installations).

• Bonding and finish: For mortar joints, check for full and uniform back-to-front fill and neat tooling. For sand joints, inspect for compaction and absence of washout. Jointing materials are the first piece to fail on most patios.

7. Drainage and Water Management

• Surface drainage: Confirm that water flows away from structures and does not pond on the patio surface. Check low spots, especially between stones and along edges.

• Subsurface drainage: We inspect for installed drains, gravel trenches, or permeable base systems. All installations will require some form of drainage, regardless of placement.

• Downspouts should be run underground away from house and any landscape installations. Downspouts are a leading cause for basement water and failed landscape installations.

8. Maintaining historical installations

• For certain historical restoration processes, the original look of the install will need to me maintained. For these projects, we will repair and reset the failed areas, while attempting to leave areas undisturbed.