TAMA 38 Choice on a Deteriorated 1963 Concrete Frame
In Ashdod, a 1963 four-storey, 16-unit residential building is a cast-in-place concrete frame with hollow-block floors. It is 600 m from the sea. A developer proposes a TAMA 38/2 demolition-and-rebuild scheme with two additional floors, eight new units, and a basement parking level. The original drawings are missing; a visual survey shows spalled concrete, exposed reinforcement on the seaward façade, and cracks at beam-column joints. The geotechnical report from 1963 is unavailable. The developer wants to start demolition in three months. The tenants, who must vacate, ask whether the building could instead be strengthened and extended under TAMA 38/1 with less disruption.
1. What investigation programme is needed before deciding between TAMA 38/1 strengthening and 38/2 demolition?
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The missing drawings make a measured survey the first step: dimensions, column and beam layout, floor thickness, foundation type, and any later alterations. The structural investigation should include concrete cores from columns, beams, and slabs; cover-meter readings; chloride and carbonation testing, especially on the seaward façade; petrographic examination where deterioration is severe; and opening up of foundations and beam-column joints. A geotechnical investigation is required because the 1963 report is unavailable and a basement is proposed. The structural engineer should then build a model to assess the existing seismic capacity under SI 413, the effect of two added floors, and the feasibility of strengthening. The architectural and planning checks run in parallel: building rights under the applicable plan, TAMA 38 conditions, setbacks, height, parking, and the tenants' rights. Only after these studies can the developer compare TAMA 38/1 and 38/2 on structural feasibility, cost, construction time, and disruption. Demolition in three months is unrealistic if the structural and geotechnical basis is missing.
2. If cores show 18 MPa concrete and columns are 25x30 cm, what structural issues arise for adding two floors, and what are the options?
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18 MPa is low for a modern frame and, combined with 25x30 cm columns, suggests limited axial and shear capacity, poor confinement, and vulnerability at beam-column joints. Adding two floors increases axial loads, overturning moments, and seismic demand. The engineer must check column capacity, joint shear, slab punching, and foundation bearing. Options include jacketing columns with reinforced concrete, wrapping with carbon fibre or steel, adding new shear walls or a braced frame, thickening foundations, or reducing the number of added floors. Some of these are intrusive and reduce lettable area; some may not be feasible with tenants in place. A TAMA 38/1 scheme may still work if strengthening is designed and priced before commitment, but the developer cannot assume that two floors are automatically available. If the existing frame is too deteriorated or the strengthening cost is disproportionate, TAMA 38/2 demolition and rebuild may be the more honest option. The architect should present the structural findings to the tenants in plain language and avoid promising a scheme before the engineer signs off.
3. What should the architect tell the tenants about TAMA 38/1 versus 38/2, and what consents and documents are needed?
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Explain the difference factually: 38/1 usually keeps the existing building, strengthens it, and adds floors or wings, so tenants may need to vacate temporarily; 38/2 demolishes and rebuilds, giving new apartments but requiring longer evacuation and a different allocation of rights. The architect should not give legal advice on ownership, taxes, or the tenants' agreement. The tenants need a lawyer and a valuer to review the developer's proposal, the allocation of new units, rent during evacuation, and guarantees. The project will need the consent threshold required by the applicable urban-renewal framework, a signed agreement with the developer, and a building permit. The architect should prepare comparative drawings and a schedule showing construction time, phasing, and temporary accommodation, and should state clearly which parts are assumptions pending structural and planning approval. Transparency about uncertainty is part of professional practice; it also protects the architect if the scheme changes after the investigations.