From Realtà Mapei International n° 66 - 15/12/2017

The Sagrada Familia

The Sagrada Familia today is a work in progress: Barcelona’s wonderful cathedral, renowned for Gaudì’s unique design, is gradually taking shape. Mapei took part in the installation of the heating flooring with its products for the installation of screeds and natural stones and with its solutions for ceramics for interiors and exteriors, along with its sealants and waterproofing products. The Sagrada Familia is due to be completed in 2025.

It all started in 1866 when Josep M. Bocabella i Verdaguer founded the spiritual Association of Devotees of San José, with a commitment to build a church dedicated to the Holy Family, and specific instructions that all the funds required should come from donations made by its followers. A few years later, in 1881, the association managed to purchase a plot of land where the sacred building would later be built. It was the architect Francisco de Paula del Villar y Lozano who initially presented the first design, which included three aisles, seven chapels and a spire. On the 19th of March 1882 Bishop Urquinaona laid the first stone of the Sagrada Familia Temple. A few years later a row broke out between Villar and the benefactors and, in 1883, its construction was entrusted to the architect Antonio Gaudí who decided to completely modify the previous design.

The Catalan architect redesigned a new layout for the basilica, this time based on five aisles, and made the entire structure more vertical and dominant. The intention of Gaudí was to make the Sagrada Familia visible from every part of Barcelona, which is why he chose to design a temple with a predominantly vertical aspect that would instantly stand out from the other civil and religious buildings in the capital of Catalonia. According to the original design, the Sagrada Familia was to have 18 towers between 90 and 170 m tall, with the last one intended to be the tallest tower ever built for a church.



From 1914, Gaudí decided to dedicate all his time working on the Sagrada Familia project and even had a small house built on the site itself so that he could always be present. On the 7th of June 1926 he was hit by a tram and died three days later. The whole of Barcelona was in mourning and the Pope agreed to Gaudí being buried in the crypt of the yet to be completed Sagrada Familia: the architect had forecast that the church would have been completed within 200 years but, unfortunately, he did not leave any complete construction drawings.

Various architects worked on the monument following his death and, since then, construction work has never been interrupted, not even during the difficult years of the Spanish Civil War. The forecast now is for construction of the Sagrada Familia, financed entirely by donations and money raised by selling entrance tickets, to be completed in 2025.


The Sagrada Familia has five main aisles and three transversal aisles which to-gether form a Latin cross. The five main aisles are 90 m long while the transversal aisles are 60 m long. The roof is still being built and the doors remain open during the day to allow visitors to enter. All this means that inside it is very cold, especially during winter. This is the rea-son why the architecture studio commissioned to follow the construction of the remaining parts of the church proposed installing a heated floor to heat the inside, thereby making the environment more comfortable for the workers and visitors.

In February, 2016 the architects commissioned to carry out a feasibility study, also invited the Technical Department from Rehau, the company supplying the heating system, and Mapei Technical Services to a series of meetings to study the possibility of installing a floor incorporating a heating system in the presbytery, which would then be extended at a later date to the other areas. After carrying out a series of site surveys, Mapei Technical Services presented a proposal for a complete installation system incorporating the supplied underfloor heating circuit.

The initial phase was to apply a new coating over a reinforced concrete substrate. The first part of the intervention was to lay the heating elements on the concrete substrate, followed by a screed covering the heating system.

After laying a metal mesh, the substrate was treated with the adhesion promoter PRIMER G in water dispersion diluted 1:1 with water. This product is an adhesion promoter that also anchors any residues of dust in place and has the capacity to prevent over-rapid absorption of water by the substrate before bonding.

At this point it was time Mapei products for the installation of ceramics and sealants were suggested:  NOVOPLAN MAXI cementitious levelling mortar was applied with a pump. This particular type of mortar contains fibre reinforcement, is free-flowing, hardens quickly and has been specifically developed to install compact underfloor heating systems with high thermal conductivity (1.727 W/mK). NOVOPLAN MAXI may be applied in layers from 3 mm to 40 mm thick and the resulting surface is suitable for installing ceramic tiles, natural stone and pre-finished wooden flooring.

Once the substrate was dry, natural stone slabs were installed using KERAQUICK S1 fast-setting cementitious adhesive with very low emission of volatile organic compounds (VOC). The joints were then grouted with ULTRACOLOR PLUS anti-efflorescence, quick setting and drying, polymer-modified mortar with BioBlock® technology to block the formation of mould and Drop Effect® technology to make joints water-repellent.

Once the intervention had been completed, the expansion joints were sealed by inserting MAPEFOAM closed-cell polyethylene foam cord along the bottom of the joints and then filling the remaining part of the joints with MAPESIL AC silicone sealant. The system proposed by Mapei was then tested to make sure it could withstand the weight of the fork-lifts used to carry out maintenance work in the Sagrada Familia.



Mapei Technical Services is also involved on a second intervention currently being carried out inside the Sagrada Familia to install the rest of the flooring. The stone type chosen in this case is considerably heavier than the previous one, which is why a different installation system was proposed.

After testing the stone in Mapei Research Laboratories to evaluate the risk of deformability and stain related to the bonding system, it was recommended to use Mapei Mapestone system for architectural stone paving. MAPESTONE 3 PRIMER cementitious bonding slurry was used to prime the surface of the substrate treated with NOVOPLAN MAXI cementitious mortar. MAPESTONE 3 PRIMER has the capacity to improve adhesion of the following layer of natural stone.

While the surface was still wet, a layer of MAPESTONE 2 fibre-reinforced cementitious mortar was applied.

A coat of MAPESTONE 3 PRIMER was applied on the backs so they would form a monolithic bond once installed.

As far as the external areas of the Sagrada Familia are concerned, Mapei Technical Services recommended using MAPESTONE TFB 60, a pre-blended mortar which is used to form screeds for architectural stone flooring with high compressive strength and good resistance to de-icing salts, freeze-thaw cycles and seawater.

Other products used to install ceramic tiles and trencadis (a type of mosaic used in Catalan modernism) in a hyperboloid tower were ELASTORAPID adhesive and KERACOLOR GG grout for joints mixed with FUGOLASTIC, while the roof was waterproofed with MAPELASTIC SMART two-component, high flexibility, cementitious mortar.

We will be sure to update you on how work is progressing in the next editions of our magazine!

For further information see

Starting on the screed

That's because for any type of flooring, being it ceramic, stone, textile, resilient or wood, the service life and functionality are highly dependent on the physical and elastic-mechanical characteristics of the substrate on which it is installed.

These properties must be defined according to a number of factors, such as the final use of the flooring, which basically means the type of flooring to be installed, the compressibility of the underlying layers and any deflections in the concrete floor slab.

Consult our technical documentation
to find out more on Mapei systems for radiating floor heating with high thermal efficiency and correct substrate installation.

On our dedicated section you can also consult Mapei suggested systems, among which a system for the installaton of ceramic tiles on heated screeds

Do you have any other questions? Contact us or find more material on this topic on our online documentation.

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