- Subfloor – A subfloor is selected for structual purposes and is the substrate (supporting layer) for the underlayment.
- Sleeper-constructed subfloor – Consists of wood subfloor installed over or on an existing concrete subfloor on- or below-grade without 18″ of well-ventilated air space.
- APA trademarked – Wood underlayments approved as suitable for the installation of flooring by APA–The Engineered Wood Association.
- STURD-I-FLOOR® – An APA-rated panel specially designed as combination subfloor/underlayment.
- Underlayment – The smooth surface used as the substrate for the floor covering.
- Subfloor/Underlayment Combination – A surface that must meet structural requirements and have a smooth surface suitable for the floor covering.
- Substrate – The smooth surface prepared to accept the floor covering, such as concrete, underlayment or existing resilient floor covering.
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