NASCLA Accredited Commercial General ContractorConcreteMedium
A concrete project manager is reviewing formwork designs for a complex architectural concrete wall. To achieve a smooth, blemish-free surface finish without bug holes or honeycombing, which type of formwork facing material is generally preferred?
- AExpanded metal mesh.
- BRough-sawn lumber boards.
- CUntreated standard plywood.
- DPlywood with a high-density overlay (HDO).
Show answer & explanationAnswer & explanation
Correct answer: D. Plywood with a high-density overlay (HDO).
Plywood with a high-density overlay (HDO) provides a very smooth, durable, and non-absorbent surface that minimizes adhesion of concrete, prevents bug holes, and allows for multiple reuses, resulting in a superior architectural finish.
Why the other options are wrong
- A. Expanded metal mesh is typically used for lath or reinforcement, not as a formwork facing material for a smooth concrete finish.
- B. Rough-sawn lumber will impart a noticeable texture to the concrete and could lead to bug holes due to absorption and irregular surfaces.
- C. Untreated standard plywood is absorbent and can lead to surface defects like bug holes, discoloration, and a less smooth finish.
Architectural Concrete Formwork
Formwork specifically designed to produce a desired aesthetic finish on exposed concrete surfaces.
- Requires high-quality facing materials.
- Minimizes surface defects.
- Often uses HDO plywood or steel forms.
Memory trick: Lumber rough, Plywood smooth, HDO perfect, Steel durable.