Courtyard Clinic: Tree Protection Versus Vehicle Access
A 0.18 ha internal courtyard between two 1970s office wings is being converted into a community health clinic. The client's program requires a 24-seat outdoor waiting area, an accessible route from the street to the main entrance, screening from an adjacent 60-space parking lot, and a 6 m by 6 m pad for a mobile vaccination tent that must be reached by a van and have 4.2 m clear height. The site has a 40-year-old Quercus rubra with a 14 m canopy near the center, finished floor 150 mm above the surrounding pavement, and a single drainage inlet at the low southwest corner. Code requires a 1.5 m clear pedestrian route, ramps no steeper than 5%, and a tree protection zone of 6 times trunk diameter. The budget is USD 180,000. The only van route that fits the site crosses the tree protection zone, and the waiting area needs shade close to the tree.
1. Identify the controlling design conflict and propose a layout that satisfies the program, accessibility, and tree protection without exceeding the budget.
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The controlling conflict is that the only van route crosses the Quercus rubra tree protection zone, while the waiting area also wants the tree's shade. Do not solve this by narrowing the TPZ; separate the two functions. Keep the accessible pedestrian route on the existing pavement line along the building wing, at 1.5 m clear width and no more than 5% slope, so it avoids both the tree and the van turning area. Move the vaccination pad to the parking-lot edge, using the existing curb cut; verify the van turning template and 4.2 m clear height there. Split the 24-seat waiting area into a 12-seat shaded cluster and a 12-seat cluster at the clinic door under a fixed canopy. Put the shaded cluster on a permeable, no-dig deck set on grade within the canopy but outside the trunk protection distance; this spreads load without excavation and avoids the 150 mm grade change. Screen the parking with a 1.8 m evergreen hedge in a raised planter outside the TPZ. Spend the budget on the deck, drainage, and canopy rather than decorative paving. If the pad still conflicts, reduce it to 5 m by 5 m and confirm with the health department.
2. The pavement falls to the southwest inlet, but the accessible route must not pond or exceed 5%. Explain how you would resolve grade, drainage, and tree protection together.
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Set the accessible route at 1.5-2% cross slope and no more than 1:20 longitudinal slope, with a high point between the inlet and the clinic door so surface water does not cross the path. The existing 150 mm floor-to-pavement step is too high for a simple threshold; use a 1:12 ramp with landings, or regrade the exterior to within 13 mm, but do not place fill over the root zone. At the ramp foot, install a linear trench drain connected to the southwest inlet. On the parking side, form a shallow 150 mm swale with a minimum 1% grade to carry water around the TPZ, not through it. Inside the TPZ, use a permeable fixed deck on pedestals; no cut, no fill, and no compaction. Direct deck runoff to a splash block outside the TPZ. Fence the TPZ at 6 times trunk diameter and hand-dig only outside it. Confirm the inlet capacity and add a 300 mm sump; if the swale cannot achieve 1%, use a slot drain. This keeps the 5% ramp limit, removes ponding, and protects the tree's roots and oxygen supply.