Installing chipboard flooring and OSB
Chip board and OSB (“oriented strand boards”) have been the constant companions to floor- and wood flooring-layers for many years, as laying surfaces for all work in floor coverings and wood flooring. To guarantee a perfect result from installing the following floor covering, installers need to pay attention to a few points.
DIN EN standard 312, “Chipboard Requirements,” has been in place since November 2003, and DIN EN standard 309, “Chipboard - Definition and Classification” since April 2005. The TKB (Technical Commission for Building Adhesives) issued their fact sheet no. 10 with the title “Wooden Composite Boards as Laying Surfaces” in September 2009. OSB is also considered here by name. However, one still encounters outdated standards regarding the installation of chipboard in day-to-day work. This applies to the standard 68 771 “Wooden Composite Board Subfloors” (version 09/1973) and the standard 68 763 “Terminology,” and the resulting designations V 20, V 100, and V 100 G for floor construction. However, these regulations are obsolete and were replaced by the ones named above.
The current relevant standards for chipboard and OSB are:
- DIN EN 13986 “Wood-based Materials - Emissions Behaviour, Labelling, Evaluation, and Conformity” March 2005
- DIN EN 309, “Chipboard - Definition and Classification” April 2005
- DIN EN 312, “Chipboard Requirements” November 2003
- DIN EN 300, “OSB – Classification and requirement definitions” September 2006
- DIN EN 634/2, “Cement-bound Chipboard” Requirements, May 2007
- DIN EN 322, “Wood-based Materials - Using Darr Method to Check Moisture Content” August 1993
DIN EN 309, “Chipboard - Definition and Classification”
It contains an overview/classification of chipboards according to manufacturer procedure, format, size, board structure, surface quality, and intended use.
DIN EN 312, “Chipboard Requirements”
According to this standard, chipboard must consist of about 90% wood and wood-based fibres. The chips in this chipboard are bound with phenolic resins, isocyanates, melamine urea resins, formaldehyde tannin resins, or urea formaldehyde resins.
Chipboard is divided into types P1 through P7 based on their intended use: Type P1 - P3 is for general use in dry areas. Type P4 - P7 is for floor covering and wood flooring work with tongue and groove.
The definitive classes for floor covering and wood flooring work are:
- P4: Boards for supporting purposes for use in dry areas
- P5: Boards for supporting purposes for use in wet areas
- P6: High load-capacity boards for supporting purposes for use in dry areas
- P7: High load-capacity boards for supporting purposes for use in wet areas
DIN EN 300, “OSB – Classification and requirement definitions”
The standard defines the OSB as consisting of long, narrow, justified filings. The top layer filings are oriented square with the substrate layer. The filings in OSB are bound with different binding agents such as PF adhesives, PMDI adhesives, melamine or urea resins, formaldehyde-tannin resins, and urea-formaldehyde resins. In accordance with DIN EN 300, types OSB 1 - OSB 4 are divided based on intended purpose as follows: The higher the count, the higher quality and more durable the product is.
The definitive classes for floor covering and wood flooring work are:
- OSB/2: Tiles for supporting purposes for use in dry areas, manufacturing of packaging material
- OSB/3: Tiles for supporting purposes in wet areas
- OSB/4: Highly durable tiles for supporting purposes for use in wet areas
DIN EN 634/2, “Cement-bound chipboards”
This standard defines cement-bound tiles as being chiefly made of conifer wood shavings, Portland cement, and additives like hemp or flax (FBP). These tiles are already sanded at the factory and equipped with groove/spring. Their high dead weight and difficult workability are detrimental.
Installation of floor covering
Virtually all types of textile and resilient floor coverings, as well as wood flooring, can be installed on pre-made composite wood board screed constructions. This includes:
- Textile floor coverings
- Resilient floor coverings
- Cork floor covering
- Multi-ply wood flooring
- Solid wood flooring/solid boards
- Design interlocking covering
- Loose lay = loose laid floor coverings with base tie-in
There are limitations in installation for heavy wood flooring (minimum thickness). It is not recommended to install ceramic tiles and natural stone on this kind of pre-made screed construction!
Types of construction for flooring structures with chipboard and OSB
Chipboard or OSB are used in three different constructions in normal building practice:
1. Floating installation of tiles in one- or two-ply design (precast screed construction)
With floating installation, it’s especially important to pay attention to moisture protection, avoiding cross joints, edge distance, a professionally prepared substrate, and minimum thickness. This means that a moisture-barring film will be installed on the supporting substrate and the wood moisture adjusted to the manufacturer's recommendation. Cross joints must be avoided at all costs, and the tiles will be installed with the top side facing up (see below). The edge distance to adjacent components must be at least 10 mm! If groove-and-tongue tiles are used, please make sure that the joints are hammered down correctly and dense. For a two-ply tile installation, watch that the tiles do not mismatch each other by more than 1/3 to 1/4 of the length of the element. In addition, they must be adhere correctly and screw-fixed or clamped into the screen to make sure of the bond. The two-ply installation of tiles prevents the individual tiles from showing under the floor covering to be installed later. This defect can occur fairly easily in one-ply installation.
2. Construction on joists or battens/sleepers
When installing on joists or battens, pay attention to the centre-to-centre distance of the timbers, the moisture protection in the construction design, and adequate edge distance. This means that the clear span of the joist should be about 40 cm each and not exceed 50 cm. The construction should be ventilated from below to avoid damage from condensation. The tile thickness must be measured so that the envisaged levels of traffic can be safely absorbed. A film must be applied to the joist to protect against creaking. This goes without saying, but is often done incorrectly: The tiles must be installed with the correct side, labelled as such, facing up.
3. Setting the tiles on the existing floorboard constructions
When setting tiles on an existing floorboard construction, it’s important to make sure that the beam construction is ventilated from behind. Will be screw-fixed in the screen (30 cm x cm/40 cm x 40 cm). A mix of bonding and screw-fixing can also be used as an alternative. The end joins will be fine-tuned to a distance of about 10-15 cm! Even if protection against creaking (film) has been installed, noises may occur. The client should be informed about this. It’s important that the construction as a whole is sufficiently bend-proof for the anticipated traffic loads. Make sure there is adequate edge space, as with all types of construction.
Complaints and their causes
If chipboard and OSB are not installed conforming to standards, this can lead to complaints later on. What does this look like? How can they be prevented?
- Board joints showing: The cause here is usually a one-ply chipboard installation, or the tongue/groove areas haven’t been glued enough. Often, there is no sufficient rear ventilation.
- Warping of floor covering or even the entire construction: Usually the edge distances or the edges areas are spackled in such a way that ventilation from behind is not guaranteed.
- Bulging and bubbling of the adhered/installed floor coverings: The reason for this is that the wrong primer has been used, and the levelling compound is breaking away with the floor covering as a result.
- Creaking of the substrate/wooden composite boards: The cause is often wood-on-wood construction. A film to prevent creaking must be installed between the joist and the board.
- Odour/mould formation: This occurs due to interactions with the binding agent used on the chipboard or OSB, or with old adhesives.
Three cases of damage from practice
Case 1: Bulging of the newly installed PVC sheet flooring
Bulges form shortly after installing PVC sheet flooring. Different causes can be responsible for this. It may be that the wrong size of notched trowel was used, so that an incorrect amount of adhesive was applied. Another possibility is that the tongue/groove areas weren’t glued correctly, and old layers between adhesives weren’t removed properly, causing an interaction. Furthermore, the gaps in the joist were filled in with debris. However, this was very damp and caused the turbulent surface. An electronic wood moisture measurement showed that the wood moisture on the joist was three times as much as the data measured on the joist.
Case 2: Tile edges are heavily showing
The cause for this type of damage is that the tile is lying single-ply on the substrate and was not installed properly as tongue-and-groove. It was subsequently set up with a cementitious levelling compound before the floor covering was installed/adhered.
Case 3: Warping throughout the construction
It could clearly be determined for this damage that all the perimeter joints for acoustic insulation were sealed with a low-slump, cementitious mortar so that the tiles could not get any ventilation from behind or expand and shrink.
The instances of damage above show that it is essential for the flooring or wood flooring installer to pay attention to the following points when installing floor coverings on chipboard and OSB if they want to achieve a professional end result:
- The chipboard or OSB construction must be visually assessed to check that it meets all contents of the standards. This applies especially if the flooring or wood flooring installer did not install the construction themselves.
- Sufficiently dimensioned perimeter joints for acoustic insulation to adjacent components must allow the construction and the floor covering to expand and shrink.
- The joist distance should be between 40 cm and 50 cm.
- The boards must be installed in such a way that the upper side of it faces up.
- Pay attention to the quality of the boards.
- Precast screed must be covered with the applicable floor covering immediately!