Attention to playgrounds!
Article by Messrs. C Mandanthi – V. Filipou (Department of Wood and Furniture Design and Technology of TEI of Thessaly)
Wood (round and sawn wood) and its products are now widely used in the developed countries of central and northern Europe, especially in outdoor playgrounds.
This is not happening accidentally, because wood is a natural and renewable material, beautiful aesthetic, elastic, with a high mechanical strength compared to its specific weight. It also has unlimited possibilities of use. The correct application of wood products to different constructions is not simple, since wood is a special material, anisotropic, hygroscopic, and requires a profound knowledge of its structure and properties. Unfortunately, in our country due to lack of training and knowledge, few construction companies use wood and its products in the right way.
Several companies, mainly importing, without having any technical staff specializing in wood technology, create sublimation and wood deforestation. Of course, in the years of the economic crisis, the situation became even more dramatic. The purpose of this article is to highlight those pathogens for which some, fortunately, few, playground companies are responsible.
It should also be emphasized that engineers (politicians, architects) should be trained more for wooden structures as well as for the behavior and properties of wood. Several times, studies of municipalities or bodies made for playgrounds contain a multitude of technical mistakes, and / or the appropriate materials are not prescribed as appropriate, depending on the type of construction or the instrument. But what technical points should be particularly taken into consideration?
Use of whitewood (spruce and spruce): Such timber should not be used in playgrounds. Glulam (composite), e.g. red pine, Oregon pine and impregnated pine are pretty good choices for their playgrounds and their organs. In Europe, the most suitable and used species are round, or sawn wood of laurel, pseudo-acuity, acacia and oak or chestnut.
Metal feet in the bases (near the ground): Metal feet in the bases are considered to protect wood from direct contact with soil and moisture. In view of the existence of a floor (proper drainage) defined by EN 1176-1, the metal feet should protrude from the horizontal floor level of more than 3 cm to protect the wood.
Glulam timber: Such timber should be used more often in playgrounds, especially in uprights (vertical wooden elements). Adhesive or composite wood must be bonded with resins for external use (see PRF, MUF, PUR, EPI) to withstand wet and dry climatic conditions. Also, when such timber is purchased, it must be accompanied by written certification.
The use of impregnated wood gluing should in any case be avoided due to the extensive detachment and tearing on the welding lines that occur after the impregnation of the composite timber.
Orientation of structures: A decisive factor that is not taken into account is the orientation that the various constructions should have. Many damage caused by atmospheric precipitation could be avoided if the playground companies incorporated into the study of the installation the correct orientation that the different structures should have in order to protect the bearing wooden elements from the weather conditions (severe northern rainfall, southern winds, solar radiation).
Dimensions of wooden elements: Many problems are also created due to the incorrect dimensions, and the general lack of standardization that exists. Mistakes in dimensions result either from splinter mistakes, since they do not calculate the right shrinkage, whether due to negligence, incorrect calculations, and sloppiness of the companies.
As a result of this, bad connections are often observed in constructions that discredit wood as a material and consequently the final construction.
Wood impregnation: The use of imported impregnated wood with unknown chemical substances and without documents is not permissible. Users (children) come into contact with wood components, and therefore it is imperative to use certified impregnating agents and / or finishing the impregnated wood components.
Also, most importantly, impregnated timber should be dried first (at least 3 weeks) before placing it on the playground. Often we have some examples of impregnated crowns, strongly drawn and deformed because they were mistakenly placed with high humidity of 30% and 40%. Therefore, there are few carefully crafted and quality wooden constructions of quality. Few, good quality companies in the industry over the last few years, despite the crisis, have invested in skilled staff as well as in appropriate equipment. This is a positive point, but it is not the rule of the Greek market. All the aforementioned data, which have been recorded through research at TEI of Thessaly (years 2014-2018), lead to the conclusion that special knowledge and experience is required in order to correctly implement a playground project, namely:
(a) a proper study has been carried out describing the technical specifications of the instruments necessary,
(b) to secure the most technically advantageous offers and not the cheaper,
(c) to control deliverables for their quality and
(d) provision should be made for a regular maintenance of playgrounds. The above to be implemented requires technical training, zeal and consistency, as well as professional ethics.