18mm T&G OSB3 Boards (2440mm x 590mm) are load-bearing structural engineered wood panels designed for high-performance subflooring, flat roofing, and heavy-duty structural applications in humid or damp conditions.

• Structural Flat Roofing & Pitched Roof Decks: Used as a solid, continuous substrate for felt, EPDM rubber, fiberglass (GRP), or green roof membranes in both warm and cold roof constructions.

• Heavy-Duty Floor Decking: Installed directly over floor joists spaced up to 400mm centers in residential, commercial, or loft conversion projects to create a rigid, flat subfloor.

• Moisture-Prone Internal Applications: Manufactured with moisture-resistant resins (OSB3 grade), making it suitable for areas prone to periodic humidity, such as utility rooms, kitchens, bathrooms, and unheated outbuildings.

• Wall Sheathing & Timber Frame Construction: Provides racking strength and structural support when fixed to timber frame wall studs prior to insulation and exterior cladding.

• Garden Buildings & Mezzanine Floors: Frequently used for constructing shed bases, workshop floors, garden room decks, and industrial mezzanine storage platforms due to its high load-bearing capacity.

Available for collection from our Rugby branch or local delivery using our own fleet.

Delivery is kerbside and the final offloading position is always subject to safe access and the driver’s discretion.

Please tell us before delivery about:

• Narrow roads or restricted entrances
• Parked vehicles or limited turning space
• Overhead cables, trees or other obstructions
• Soft, sloping or unsuitable ground
• Any other access concerns

Enter your postcode on the product page to check your delivery area. We’ll confirm the delivery date after your order is placed.

What does the "OSB3" rating actually mean?

OSB3 stands for Oriented Strand Board Class 3. This indicates it is a precision-engineered, load-bearing panel designed specifically for use in humid or damp conditions. It uses moisture-resistant synthetic resins to bond cross-oriented wood strands, preventing delamination when exposed to ambient moisture.

What is the difference between OSB3 and P5 chipboard?

While both are moisture-resistant subfloor options, OSB3 is generally stronger, stiffer, and offers higher racking resistance than chipboard of the same thickness. OSB3 is also more suitable for structural roofing applications and external sheathing, whereas P5 chipboard provides a smoother surface finish for internal living spaces.

Do the tongue and groove joints need to be glued?

Yes, gluing the T&G profiles with a PVA or expanding polyurethane joint adhesive is recommended for flooring applications. Bonding the interlocking edges creates a continuous structural membrane, increases overall floor stiffness, and prevents squeaking caused by board friction.

Is OSB3 fully waterproof for outdoor use?

No, OSB3 is moisture-resistant, not waterproof. It easily handles exposure to weather during construction and high-humidity environments, but it should not be left permanently exposed to constant rainfall or standing water without a protective waterproof membrane or finish.

Which side of the board should face upwards when installing?

For flat roofing, the textured or mesh-patterned side should face up to provide a non-slip working surface. For indoor flooring, the smoother, sanded face can face up to give a flat base for your final floor coverings, though either side can take load effectively.

How many boards do I need to cover a specific area?

Each board has a gross face area of 1.44 m², but because the tongue fits into the groove, the usable coverage is approximately 1.38 m². Divide your total floor or roof area by 1.38, then add 10% to account for cutting waste.