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The Maintenance-Free Bathroom

By Joseph P. Joy
As published in Designing with Tile

Nothing is more frustrating to an owner of a newly installed tile covering than pre-mature cracks and on-going maintenance. This article will explore techniques to eliminate these cracks and regular maintenance except for cleaning of the tiled surface. The picture attached is an example of a bathroom that was constructed in a manner that cracks will not develop, will require no caulking and mold and mildew will not develop later.

The main difference this bathroom and any other is that proper planning was incorporated in the layout of movement joints and those movement joints were the pre-fabricated. Caulking was not used anywhere. First lets define a movement joint. They are a necessary component in any tiled installation. They are simply intentional interruptions in the tiled surface. In most cases, movement joints are filled with elastic joint sealants. Every one is familiar with the most common joint in any bathroom: the caulk around the bathtub. We are familiar with it because unsightly mold and mildew can attack it and the required maintenance is often tricky to do neatly.

Why movement joints?

Construction elements are subject to changes in shape. The most frequent causes for changes in shape are drying out of the sub-structure, the loading of construction elements, and changes in either the moisture content or temperature.

Moisture changes in concrete are caused by excess mixing water that evaporates over time, causing the construction elements to contract. This phenomenon is referred to as "shrinking." Typically under normal climatic conditions, the shrinking process is basically complete after two years. In addition, load-bearing construction elements are subject to increasing stresses as the building is progressively erected, and then through its actual use. The stress is caused first by the weight of the structure itself, and later by the working load imposed. Coupled with all this are thermal length changes. When temperatures increase, construction elements tend to expand, and when temperatures fall, they tend to contract. These temperature change-related processes are called "swelling" (expansion) and "shrinking" (contraction), and they change the dimensions of the construction element. With the warming of construction elements, "expansion" occurs, with cooling "reduction" (shortening) occurs. The degree of the deformation will differ depending on their expansion coefficient.

In addition one should also note that the above-mentioned shape changes can occur in combination. Stresses are generated by loads and shape changes of the construction elements, and by the differing behaviors of their raw materials. Theses stresses must be minimized in surface coverings through proper positioning of movement joints.

There are three types of movement joints;

Field Boundary Joints (surface control joints) divide the covering and should be installed from the surface of the covering down to the load-bearing substrate, or to the covering of the insulation or the waterproofing membrane.

Edge Joints, which delimit the covering at the interface with walls or construction elements that penetrate the covering, should be installed like the field boundary joints.

Junction Joints may be required between coverings or surfacings and adjacent to construction elements as well as fixtures. In general, movement joints in ceramic coverings are arranged: over structure joints at the same spot, at wall junctions, pillars or other construction elements which penetrate the covering surface (edge or junction joints), at points where the sub-structure materials change, at inner and outer corners of the covering, with continuous coverings at ceiling level (in general at the lower edge of the ceiling).

To create the maintenance free bathroom we will be only concerned with the edge and junction-type joints.

The theory:

In order to keep the movements occurring in the joint as low as possible, it has proven advantageous in practice to fill the elastic joints with flexible sealing material as late as possible. In so doing, one must ensure those shape changes of the adjacent construction elements have as far as possible been completed by this time.

And in practice . . .

In everyday practice at construction sites, however, it is found again and again that, under today’s tight scheduling pressures, this recommendation concerning the latest possible filling of the joints is generally ignored. Another factor is that returning several times to the construction site would generate significant additional costs for the installer. Another weak point in practice is the often omitted preliminary treatment of the surfaces to be joined with "primers" that ensure a better adhesion to the tile edges. All of these are facts that speak in favor of using maintenance-free movement joints.

The fundamental point is that movement joints should be dimensioned and structured in such a way that they fulfill their function as permanently as possible. That function is to absorb movements and shape changes of the construction elements adjacent to the joint and the joint sealant. The drawbacks of sealing material.

Until now, joint sealing materials have been used for narrow joint widths, as well as for joints that are exposed to only slight (or no) mechanical stress. Most often these are injectable sealing materials, including the alkaline or neutral cross-linking silicones, polyurethanes or acrylates. They are distinguished according to their physical - that is, the plastic or elastic sealing materials - and chemical characteristics, as well as according to the raw material basis, which fundamentally determines their properties. One advantage of the silicones is their easy processing, while their disadvantage is a tendency to develop mold on the joint surface over time. Other disadvantages are polyurethanes react sensitively to the effects of UV, and must therefore be protected by stabilizers. Until the development of a surface skin after their application, acrylates are sensitive to direct exposure to precipitation. Protection against moisture is critical during this curing period.
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Further, it should be observed that certain elastic joint sealing materials tend to release components, which are deposited in the edge area of the joint and on the adjoining surface. There, in combination with soot and dust, they form ugly streaks of dirt.

Nevertheless, all joints with elastic sealing materials, including even the "simple" silicone joint around the edge of a bathtub, have one thing in common : they can by no means be characterized as "impermeable". Therefore they cannot be regarded as an effective waterproofing measure. Joints that are filled with elastic joint sealing compounds, depending on the stress to which they are exposed, will require ongoing maintenance.

Maintenance-free movement joints

The goal of designers and installers should be to offer owners long-term, functional solutions which in terms of technology embody the current state of the art. What owner would not be interested in a Maintenance free bathroom?

For several years now, pre-made movement profiles are available for this problem area. They are obtainable for screed, covering, junction and edge joints. Typically, the products are made of recycled rigid PVC with movement zones of flexible polyethylene.

The most critical areas are the corners. The edge joints between floor tiles and skirting or wall tiles are also movement joints, for these are areas where relatively large movements occur. In addition, horizontal expansion-shrinkage stresses arise through various temperature influences. When a built-in floor heating system is added to the overall picture, the different temperatures in the covering construction produce more or less significant buckling and length changes of the covering surface. This creates movements on the edge joint. If such joints are filled with elastic material, they will inevitably split open. Apart from the ugly appearance, a gaping joint crack opens the way to dirt and cleaning water. Such areas quickly become infested with vermin.

In addition, there are special junction profiles for permanently flexible joining of tile coverings to construction elements and fixtures like bathtubs, door frames or window elements. These products have proven themselves to be UV resistant for years, and are therefore suitable for outdoor use. In addition, they are resistant against attack by mold and bacteria, as well as against the kinds of chemicals, cleaning agents and disinfectants that commonly come into contact with tiles.

Summary

It should be pointed out that the designers are principally responsible for the arrangement of the movement joints. As an industry we cannot delegate the responsibility. Too many opportunities have been lost to pre-formed plastic bath surrounds. Their popularity is growing because they have no ongoing maintenance costs. We have the tools to offer a tiled maintenance free bathroom, it is just a matter of getting the word out.



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