To determine whether you have a concrete or timber (wooden) subfloor, you can follow these steps:

1. Visual Inspection:
   • Access an Edge: If possible, access an edge of your floor where it meets a wall. Look at the cross-section of the floor. A concrete subfloor will have a gray, stone-like appearance, while a wooden subfloor will have a lighter, wood-like appearance.
   • Check for Floor Covering: If you have existing floor coverings, such as carpet, laminate, or vinyl, you can carefully lift a corner or edge to see what’s underneath. In many cases, the type of subfloor will be visible.
2. Knock Test:
   • Find an inconspicuous area of your floor.
   • Gently knock on the floor with your knuckles or a small tool.
   • Listen to the sound it makes. A concrete subfloor will produce a solid, dull, and low-pitched sound, while a wooden subfloor will produce a hollow, higher-pitched sound.
3. Ventilation Access:
   • If you have a basement or crawl space, you might be able to access the subfloor from below. This can provide a direct view of the subfloor material.
4. Ask a Professional:
   • If you are still unsure or if access to the subfloor is limited, consider hiring a professional flooring contractor or home inspector to assess and identify the subfloor material for you.
5. Consult Blueprints or Records:
   • If you have access to the blueprints or records of your home’s construction, these documents may indicate the type of subfloor used.

Keep in mind that some homes may have different subfloor materials in different areas. For example, the subfloor in your basement may be concrete, while the upper floors have wooden subfloors. Additionally, in some cases, there may be multiple layers of flooring materials (such as plywood or particleboard) on top of the subfloor before the final floor covering is installed.

Identifying the subfloor material is essential when planning to install new flooring, as different types of flooring may require specific preparation or underlayment materials.