TN 10.23 - Heavily Trafficked Floors & Hard Wheeled Traffic

INTRODUCTION
Ceramic tiles are easy to install, hard wearing, durable and perform well under heavy pedestrian and wheeled traffic. However, in the case of heavily loaded trolleys with small hard wheels, excessive forces can be exerted which could result in impact damage.
DEFINITIONS
BS 5385-3 defines the difference between light and heavy traffic as follows:
Light Traffic = Low density foot traffic e.g. domestic and office locations
Heavy Traffic = High density foot traffic and/or heavy static (standing) or dynamic (moving, dropped or dragged) loads e.g. supermarkets, shopping centres etc.
TRAFFIC AND LOADING CONSIDERATION FOR TILED FLOORS
The following advice is given in BS 5385-3; 2014 Design and installation of internal and external ceramic and mosaic floor tiling in normal conditions – Code of practice;
“6.4.2 Traffic and load conditions
“Floor loading should be considered as heavy if heavy cleaning equipment, hard-wheeled trolleys, etc., are to be used.
Light loading should be considered as normal low-density pedestrian traffic, e.g. domestic and office locations.
Heavy loading areas should be considered as where high-density pedestrian traffic, and/or heavy loads, static, moving, dropped or dragged, are likely to occur, e.g. in supermarkets, shopping malls, engineering premises and garages for heavy vehicles.
6.4.3 Resistance to mechanical failure
6.4.3.1 Resistance of tile bedding
NOTE 1 Where heavy loading is likely, and particularly where the moving of heavy loads is contemplated, adhesion to the base is crucial.
The tiles should be solidly bedded so that, as far as possible, they are free from voids to ensure good adhesion to the base.
NOTE 2 Greater resistance to loading can be achieved by the use of thicker flooring tiles with increased impact resistance, bearing in mind also that the joints between the tiles are usually the most vulnerable part of the flooring [see 6.4.3.2c)3)].

6.4.3.2 Resistance of tiling
Abrasion, compression and impact can operate singly, but they are often to be found in various combinations; the relevant mechanical properties of flooring should be considered and are as follows:
a) for resistance to abrasion: physical toughness of the flooring itself and a surface free from irregularity in level;
b) for resistance to compression: strength and thickness of tile, solidity and strength of bed and compressive strength of sub-floor;
c) for resistance to impact: in addition to the properties given in a) and b), the following factors are also important:
1) Within the normal tolerances of the flooring tiles used, the individual tiles should be laid to a true plane. Therefore, a true base to SR1 is a necessary pre-requisite.
2) The flooring tiles should be solidly bedded so that, as far as possible, there are no voids beneath the tiles.
3) Joints between ceramic tiles should be as narrow as possible, but not less than 3 mm, appropriate with the tiles and grout being used.
4) The maximum joint width should not exceed 10 mm. Proprietary grouts specially formulated with enhanced resistance to impact and abrasion and low shrinkage should be used”.
IMPACT DAMAGE
Historical research carried out by the British Ceramic Research Association (BCRA) on The Impact Resistance of Ceramic Tiles and Flooring using both the dropping ball and Schmidt Concrete Hammer method defined the following areas;
Heavy duty areas, such as Factory loading areas, and garages
Normal or medium duty areas, such as pedestrian walkways and lightweight trolleys.
It is important to note that all floor tiles should be fixed in a solid bed of tile adhesive. The use of certain types of levelling clips could pull up the tile edges from the adhesive bed creating voids.
Any voids will be potential points of weakness under load.
Tile edges are particularly vulnerable to impact damage caused by hard wheeled traffic particularly when adjacent to flexible movement joints.

HARD WHEELED TRAFFIC CALCULATIONS
The static force exerted by wheels on a flat, even floor depends upon;
1. The weight of the trolley/vehicle
2. The number of wheels
3. The contact area between the wheels and the floor surface e.g. point loading vs.
evenly distributed load
Here is an example calculation to illustrate the effect of contact area of the wheels on the floor;
1. A 5 wheeled trolley with a total load of 400kg. Each wheel is 50mm wide with an approximate contact area with the floor of 5mm
Area of contact for each wheel with the floor = 50x5mm = 250mm²
Force exerted (Newtons) = 400 x 9.81 Newtons = 3924N. For each wheel = 3924 = 785N
5
The force exerted per wheel is therefore, = 785 = 3.14N/mm² or 455 psi
250
If the contact area of the wheels was 10mm x 50mm i.e. 500mm², the static load = 785
500
= 1.57Nmm² or 228 psi (Half the load per each wheel).
As the contact area between the wheels and the floor increases, the impact of the load on the floor decreases and vice versa.
For an increase in the number of wheels with the same contact area per wheel and load (400kg);
2. An 8 wheeled trolley with a total load of 400kg. Each wheel is 50mm wide with an approximate contact area with the floor of 5mm
Area of contact for each wheel with the floor = 50x5mm = 250mm²
Force exerted (Newtons) = 400 x 9.81 Newtons = 3924N. For each wheel = 3924 = 490.5N
8
The force exerted per wheel is therefore, = 490.5 = 1.96 N/mm² or 284 psi
250
Further advice can be found in BS 5385: Parts 1-5 the code of practice for wall and floor tiling and further advice should be sought.
TECHNICAL ADVISORY SERVICE
For free expert guidance on the use of BAL products, or any aspect of ceramic tiling with BAL products, contact the BAL TECHNICAL ADVISORY SERVICE on 01782 591120.

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