Expansion joint: What is it and what is it for?

When two built volumes adjoin, differences in settlement or expansion can generate concentrated stresses in the party wall. For this reason, expansion joints between buildings are resolved by leaving a 10-20 cm gap free of rigid materials, protected on the roof with sloping gutters to drain water, and on the façade with metal or PVC profiles incorporating rubber strips. This ensures that each building evolves without transmitting movements to the neighbor or allowing leaks at the meeting point.

However, not all gaskets serve the same purpose and are not placed in the same location. There are three main types:

1. Structural joints. They are the extension, in the ceramic tiling, of the joints foreseen in the supports and underlying structures (slabs, columns, beams). These joints must be respected in all their depth and width, crossing all the layers of the system – from the tile to the bonding mortar or any decoupling or insulation sheet – so that each fragment can move independently, without transmitting forces to the adjoining panel.

2. Perimeter joints. They delimit the edge of the tiling from rigid construction elements -walls, columns, closings- that do not share the same capacity for movement. Thanks to this separation, displacements of the wall do not affect the flooring or the baseboard, and vice versa. In dwellings, when the surface to be covered is less than 10 m², these joints can be eliminated for reasons of design or hygiene, provided that the tiles are 5 mm from the vertical element. In any other case, the perimeter joint must be at least 6 mm wide and reach the separating layer to fulfil its function.

3. Intermediate joints. They divide the tile covering into smaller pieces – usually rectangular or square – so that each tile fragment can react to thermal and humidity changes with less effort. In installations without radiant heating, they are usually spaced every 8-10 m linearly, with depth also down to the separating layer. In floors with underfloor heating, this subdivision is adjusted to grids of about 25 m² (or every 5 m linear) to accommodate the temperature and movement of the heating system.

Given that a tile covering is, in reality, a multilayer system (tile, adhesive, distribution mortar, decoupling or waterproofing sheets, insulation), the correct execution of these three categories of joints-structural, perimeter and intermediate-is key for each layer to fulfill its mission without interfering with the others. In this way, internal stresses are minimized and the useful life of the pavement and the building itself is maximized (they are a perfect complement to decoupling sheets that protect the ceramic and the structure).