Suspended timber floor

[edit] Introduction

Suspended timber floors are sometimes referred to as hollow timber floors. Suspended timber floors are not the same as floating floors or raised floors.

This is a method of floor construction in which timber joists are supported by load bearing walls or foundations and typically covered with floorboards on the top. This creates a gap to accommodate ventilation and reduce the chance of damp accumulation.

[edit] History

This type of construction was commonly used during the Victorian era. It is still found in older buildings and is sometimes used to create a level ground floor when ground surfaces are uneven.

In the 1920s, improved construction methods resulted in refinements to suspended timber floors. Floor joists were regularly supported on honeycombed sleeper walls and joists were not in contact with external walls.

For more information on load bearing sleeper walls, see Sleeper wall

[edit] Key points

To prevent moisture from accumulating in the gap between the floor and the surface below, ventilation is essential. This can be accomplished by fitting airbricks in external walls.

Additional guidance for suitable procedures for suspended timber floors can be found in Building regulations Part C: Site preparation and resistance to contaminants and moisture. This document covers the weather-tightness and water-tightness of buildings, subsoil drainage, site preparation and additional issues relating to damp proofing and ventilation.

For more information on dealing with damp proofing, see Damp proofing buildings

[edit] Issues of suspended timber floors

In addition to damp, there are two common issues associated with suspended timber floors: drafts and noise.

[edit] Drafts

Gaps associated with timber or hollow floors increase the tendency for drafts to occur. These can be tackled by methods including:

• Draft excluders. These include synthetic fillers and draft proofing adhesive strips.
• Insulation. Building regulations now require insulation in timber floors. For more information, see Floor insulation
• Tongue and groove floorboards. This technique produces a strong bond that is suitable for floating floors. For more information, see Tongue and groove joint
• Underlay and carpet.
• installation of a subfloor on the underside of the joists.

[edit] Noise

It is not uncommon for suspended timber floors to creak over time, especially when joists move and nails loosen. Resolving this issue can be complicated and may involve reinforcement or replacement.

See: Sistering floor joists.

[edit] Related articles on Designing Buildings Wiki

• Beam and block floor construction.
• Damp-proof course.
• Floating floors in buildings.
• Insulation for ground floors.
• Load-bearing wall.
• Sistering floor joists.
• Sleeper wall.
• Sprung floor.
• Subfloor.
• Tongue and groove joint.
• Types of flooring.