Subfloor
|
| Workers instal a subfloor for a home being built as part of the Southeast Missouri Farms Project, 1938. |
Contents |
[edit] Introduction
The subfloor is the initial layer of solid material placed just above the joists or other structure of a building.
Some structures may have solid hardwood flooring that is attached directly to the joists. This surface essentially serves as the subfloor.
Others may have a solid concrete foundation that serves as the subfloor. Concrete slabs that form the ground floor of a building may be either supported on beams (called a suspended slab) or supported directly on the subsoil (via hardcore, for example) called a ‘ground-bearing slab'.
Additional structure is sometimes installed over concrete slab subfloors in order to provide a level foundation that’s suitable for the installation of underlayment and flooring. This type of structure may be used when bearing conditions require it or groundwater is present.
Placing a solid subfloor over the joists, covering it with underlayment and then layering that with flooring provides a more stable surface. It also helps to assure that the joists support most of the load of the floor.
[edit] Types of subfloor
Plywood is the most common material used for subfloors. Plywood has several properties that make it a useful and popularfor this purpose, including:
- High strength.
- High panel shear.
- Flexibility.
- Moisture resistance.
- Chemical and fire resistance.
- Impact resistance.
- Insulation.
The thickness of a plywood subfloor depends on the distance between joists. Thinner plywood can be used when joists are close together, but slightly thicker plywood is recommended when there is more than 40cm between joists.
Subfloors can also be made from oriented strand board (OSB). OSB has similar properties to plywood and is suitable for load-bearing applications. It can be more cost-effective than plywood. Impermeability to water can be achieved through the use of additional membranes.
Another type of subfloor is high-performance engineered panels. Like plywood and OSB, these panels are designed for load bearing applications. They have built in moisture resistance and are manufactured with special resins to reduce other issues - such as swelling - associated with some subfloors.
[edit] Problems with subfloors
Issues with subfloors can arise due to problems with installation, use of unsuitable materials or damage caused by dampness. These problems can be minor (resulting in squeaking or sagging) or they can be major (resulting in significant movement or total failure).
Moisture is one of the most common problems associated with subfloors. Signs of subfloor moisture problems include:
- Sunken sections.
- Squeaking.
- Smelling damp.
- Shifting or bouncing floors.
- Rocking or loose fixtures and fittings.
- Cracking tile flooring.
- Dipping or buldging.
- Bubbling linoleum floor.
A vapour or moisture barrier installed over the subfloor can sometimes help to reduce seasonal fluctuations brought about by changes in humidity and heat, but serious moisture issues may require more significant remediation measures including subfloor replacement.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
The average kinetic energy of molecules
Temperature in buildings, explained on DB
Women and unequal pay in project management
Main barrier to entering the profession, new study reveals.
IHBC’s response to Parliamentary Committee
On Levelling-Up and Regeneration Bill.
Finalists for 2022 CIOB Awards revealed
Over 70 managers and organisations shortlisted for the 14 awards.
Types of building sensors on BD
From biometric to electrical current, chemical and more.
Government mandates detectors in rented homes
Changes are due to come into force on 1st October 2022.
80% of major government projects are rated red or amber
Heed advice and insight of this report IPA tells the government.
The end of the games but continued calls for action
From the Commonwealth Association of Architects.
CIOB respond to the government call for evidence
For the Levelling Up, Housing & Communities Committee.
How are buildings and their occupants responding to extreme heat?
BSRIA's Technical Director reflects on recent weather patterns.
Landownership in England in 1909
A national valuation to fund old-age pensions.
The world’s largest Commonwealth memorial to the missing.
Long after the end of the defects liability period.
BSRIA Occupant Wellbeing survey BOW
Occupant satisfaction and wellbeing in buildings.
Geometric form and buildings in brief
From the simple to the complex.
Understanding the changing nature of insulation
And the UK Government guidelines.
Three year action plan to improve equity, diversity and inclusion
Commitment agreed to by major built environment bodies.
The Construction Route – what needs to change?
Electrical skills, low carbon, high-tech and the building services revolution.
Deep geothermal power possibilities
Ultra-deep drilling with millimeter-wave beam technology.
BSRIA Briefing 2022- From the outside looking in
Looking at the built environment from space.
Competence requirements for principal contractors and designers
BSI standards 8671, 8672 and 8673.
Bringing life to burial grounds.
From failed modernism to twenty-minute neighbourhoods.
Design chill and design freeze
The gates process and change control.