RECOMMENDATIONS
FOR LAYING CERAMIC TILES
Ceramica Sant'Agostino intends this guide to provide some useful advice for
installing and cleaning its products. We believe that this manual will help to
prevent a number of problems which may arise during laying of the tiles, or even
earlier during preparation of the substrate or screed, which is the foundation for
achievement of the desired results in terms of appearance once the tiles themselves
have been installed.
To ensure that tiles are laid to the highest standards, these instructions cover the
following stages:
•
type of substrate;
•
stages of the laying process;
•
application method;
•
cleaning, care and protection.
1. TYPES OF SUBSTRATE
The substrate is the surface on which the floor is to be laid.
When laying tiles it is essential to consider the type of substrate, which generally
consists of:
i. Concrete substrate (screed laid over a reinforced concrete floor)
ii. Existing floor covering
i) LAYING TILES ON CONCRETE SUBSTRATES
The first operation required before the tiles can be installed is laying of the screed,
which must be of good quality and properly levelled if the final floor is to look good
and prove durable.
The screed is of variable thickness and generally consists of a mixture of water,
cement and sand, or a premixed mortar.
There are different types of screed:
-
BONDED: screeds which adhere directly to the supporting substrate.
-
UNBONDED: a screed at least 35/40 mm thick, laid on top of an additional layer
which separates it from the supporting structure. This separating layer may
consist of a vapour barrier or a layer of heat insulation/soundproofing material
(in this case, the screed is defined as a FLOATING SCREED). In addition, heating
coils can also be sunk into the screed (to create a HEATING SCREED).
When possible (depth available at least 35/40 mm) it is generally preferable to create
an UNBONDED SCREED, since it will be unaffected by the inevitable deformation or
settling of the load-bearing structures.
Bonded Screeds
If the depth available for creation of the screed is limited (<35 mm), the screed
must be bonded to the substrate. To ensure a strong screed well bonded to the
substrate, an anchor layer of cement slurry should be applied before the screed,
made by mixing a synthetic rubber latex such as MAPEI PLANICRETE with water and
the cement used for mixing the screed itself.
The screed is then laid over the slurry before it sets.
Unbonded Screeds
When laying this type of screed, the first step is the application of the separating
layer, consisting for example of polyethylene sheets which create a slip surface,
preventing the screed from bonding with the underlying substrate.
A layer of a soft material (e.g. expanded polystyrene 1 cm thick) must also be placed
around the walls and any pillars before the screed is laid.
In the case of FLOATING screeds laid over insulating material, a welded reinforcing
mesh must be inserted in the screed to reduce the load on the insulation, which
offers very little mechanical resistance.
For HEATING screeds of the sand and cement type, a superplasticising admixture
such as MAPEI MAPEFLUID N200 must be added to the mixture to ensure perfect
incorporation of the heating coils and improve thermal conductivity.
As an alternative, special cement binders such as MAPEI MAPECEM or TOPCEM,
or premixed ready-mixed mortars such as MAPEI MAPECEM PRONTO or TOPCEM
PRONTO, which do not require the addition of superplasticising agents, may also
be used.
When laying this type of screed, a depth of at least 2.5 cm must be ensured above
the heating coils, and before laying the tiles it is absolutely essential to switch the
heating system on to check its operation and complete drying of the screed.
Laying the screed for best results
Laying of the screed is of vital importance in the creation of a level tile installation
surface.
If pipelines are laid inside the screed, a depth of at least 2.5 cm must be assured
above them, and a light metal mesh must be laid across them to limit cracking.
Before the screed is laid, level marker strips must be placed for use as reference for
the creation of a flat, level tile laying surface; after this the screed can be laid and
then compressed and levelled with the aid of a bar.
The surface must be finished with suitable tools to create a smooth, perfectly level
surface; do not over-trowel as this will bring water to the surface, cause bleeding
and reduce the surface’s porosity too far.
Where necessary, when laying screed on large areas, create expansion joints
whenever possible by cutting the screed through about 1/3 of its thickness into
sections of about 20-25 m
2
(indoors) and 9-16 m
2
(outdoors).
Before laying the floor tiles, it is essential to check that the substrate is:
-
MECHANICALLY STRONG: the screed must be solid throughout its depth
and have satis factory mechanical strength. As a guideline, the compression
strength of a screed on which ceramic tiles are to be laid must be at least 20 N/
mm
2
in residential buildings and 30 N/mm
2
in commercial premises.
-
CLEAN: there must be no grease, oil, wax, rust, paint, plaster marks, loose parts
or anything else which might prevent optimal bonding of the floor covering.
-
FREE FROM CRACKS: any cracks or gaps in the screed before laying must be
carefully filled with suitable products, e.g. MAPEI EPORIP.
-
CURED: The screed must have stopped shrinking due to water loss before the
tiles are laid, as otherwise cracking may occur after installation of the floor
covering, damaging it by causing it to detach or break. The curing time for a
conventional sand and cement screed is about 7-10 days for every centimetre
of its thickness (e.g. 28 days for a screed 4 cm deep). Curing times can be
reduced by adding special products of the type listed below to the screed mix:
To correct any unevenness in the ground slab or existing floor, a layer of levelling agent should
be used.
When installing tiles indoors, excellent results can be obtained with the aid of levelling cements,
such as:
-
MAPEI-ULTRAPLAN (for thicknesses from 1 to 10 mm)
-
MAPEI-MAXI-ULTRAPLAN (for thicknesses from 3 to 30 mm)
3. PREPARING THE SUBSTRATE
Before applying the levelling cement, check the conditions of the substrate and proceed as
indicated in the table below
5. INSTALLING THE TILES
Porcelain tiles have vitrified surfaces with virtually no porosity even on the underside (the side in
contact with the substrate/screed); this means that the tilebonds less effectively with traditional sand
and cement mortar.
We therefore recommend laying with adhesive, which offers better guarantees of good results than
the conventional method.
The products chosen for laying the tiles must be selected to suit the deformability and characteristics
of the substrate, the size of the tiles and the laying environment (see tables on following pages).
It is always best to lay tiles with wide joints, and plan expansion joints between them (about every
20-25 m
2
indoors and every 9-16 m
2
outdoors).
The laying procedure consists of the following stages:
a. preparation of the substrate
b. preparation of the adhesive
c. application of the adhesive and laying of the tiles
d. grouting of the joints
e. suggestions for laying outdoors
f. cleaning (page 606)
We will now examine these steps one at a time:
a. PREPARATION OF THE SUBSTRATE
The surface must be perfectly flat without cracks or flaking, and absolutely clean; all loose parts must
be removed with great care. When laying on special types of surface such as gypsum plasters a primer
must be applied if a cementitious adhesive is to be used.
b. PREPARATION OF THE ADHESIVE
This step is necessary when using powder adhesives or dual compound adhesives (ready-to-use paste
adhesives only need stirring).
The aim of the adhesive preparation stage is to obtain a perfectly smooth, fairly fluid mixture which
will be easy to apply and in which all the ingredients will be able to perform their functions effectively.
In this stage it is vital to follow the producer’s instructions with regard to proportions and application
methods. Remember that once the mix has been prepared, it can only be used for a limited time
(known as the “pot life”). This parameter may depend on ambient conditions, and the temperature in
particular, but reference should always be made to the producer’s technical specifications.
c. APPLICATION OF THE ADHESIVE AND LAYING OF THE TILES
Spread the adhesive on the substrate using a toothed trowel. Choose a trowel which allows the
underside of the tiles to be wet effectively. For outdoor ceramic floor or wall tiles, tile sizes above 900
cm
2
, floors subject to heavy loads or when applying in swimming-pools and pools, also spread the
adhesive on the back of the tile to ensure that it is wet completely.
When laying tiles take care to comply with the adhesive open time stated in its technical information,
remembering that it will vary depending on ambient conditions during laying and the type of
substrate.
Keep checking that no skin has formed on the surface of the adhesive and that it is still fresh; otherwise
refresh the surface by running the toothed trowel over it again.
The adhesive’s adjustability time, during which corrections can be made to tile positions, is also stated
in its technical information.
d. GROUTING OF THE JOINTS
This should be done using a rubber or plastic trowel, to ensure complete, even, compact filling of the
joints between the tiles.
Joints should be grouted with specific coloured premixed fillers, since they offer considerable
advantages over the cheaper sand and cement grouting cements, including the possibility of colour
matching with the tiles and lower porosity, meaning a reduced tendency to trap dirt.
Below are some guidelines concerning the type of grout which can be used:
•
Residential buildings:
MAPEI KERACOLOR FF – or MAPEI ULTRACOLOR PLUS (CG2 under EN 13888)
•
Commercial buildings:
KERACOLOR FF – MAPEI (CG2 under EN 13888), with suitable liquid additives such as MAPEI
FUGOLASTIC – MAPEI or ULTRACOLOR PLUS – MAPEI (CG2 under EN 13888).
For special fields of application, when a watertight, non-absorbent grout with high resistance to acids
is required (e.g. masonry kitchen worktops, shower cubicles, etc.) dual-compound epoxy mortars such
as MAPEI KERAPOXY or KERAPOXY DESIGN MAPEI can be used.
587
586
INDEX
TYPE OF SUBSTRATE
_____________________________
Normal and fast-setting
cement screeds
_____________________________
Existing floors
SUBSTRATE PREPARATION
_____________________________
- Loose surfaces must
be removed or, where
possible, consolidated
with PRIMER MF or with
ECOwPRIM PU 1K;
- Spread QUARTZ 1,2 or
clean, dry sand over the
whole surface treated with
primer while still fresh.
In all cases, good quality
cement screeds must first
be treated with PRIMER G
diluted 1:2 with water
_____________________________
Treat with MAPEPRIM SP or
with ECOPRIM T after cleaning
with suitable detergents and
mechanical sanding.
TIME REQUIRED
BEFORE LEVELLING
_____________________________
Depending on temperatures,
on
surfaces treated with PRIMER
MF; levelling compounds can
be applied after 12-36 hours.
_____________________________
The levelling compound must
be applied on ECOPRIM T dry
as soon as the MAPEPRIM SP
becomes transparent, (while
it is still sticky and will receive
imprints).
MAPECEM/MAPECEM PRONTO
Special premixed mortar
and binder for screeds,
fast-setting and fast-drying,
with controlled shrinkage
Time required before laying:
3 hours
TOPECEM/TOPECEM PRONTO
And binder for
screeds, normal-setting and
fast-drying, with controlled
shrinkage
Time required before laying:
24 hours
ii) EXISTING FLOOR COVERING
For ceramic tiles to be installed over an existing floor covering, the paving already in
place must be perfectly bonded to the substrate and free from cracks.
If these conditions are met, the substrate must be prepared by cleaning the old
floor with a water and caustic soda solution or an alkaline detergent (such as FILA
DRASTIC, diluted at from 1:2 to 1:5 depending on the degree of dirt), followed by
rubbing down if necessary.
If these initial conditions are not met, the tiles which are becoming detached must
be removed, any cracks in the substrate must be filled by casting MAPEI EPORIP, the
existing floor covering must be cleaned as described above, and the gaps created
must be filled using a fast-setting levelling compound such as MAPEI ADESILEX P4
or MAPEI NIVORAPID.
2. SUBSTRATE FLATNESS
As already stated, it is essential to ensure that the subfloor is flat and level to obtain
optimal results when laying edge-ground tiles. Otherwise, the defects in the
subfloor would create unacceptable geometrical errors in the finished surface.
4. APPLYING THE LEVELLING AGENT
a. Apply a single coat of the cement mix with a large metal trowel or scraper, keep ing the
trowel at a slight angle to obtain the thickness required.
Thanks to their self-levelling properties, ULTRAPLAN and ULTRAPLAN MAXI are able to
eliminate undulations in existing floors or screeds, and even the smallest flaws.
b. In case of large surfaces, do not level over the expansion joints in the substrate/screed.
Other recommendations when using levelling compounds are:
1. the times required between application of the levelling compound and laying of the tiles
are:
2. fast-setting thixotropic levelling cements can be used to correct flaws in small areas of
substrate. We recommend: 2. fast-setting thixotropic levelling cements can be used to
correct flaws in small areas of substrate. We recommend:
ULTRAPLAN 10
_______________________________
About 12 hours
ULTRAPLAN MAXI
_______________________________
About 2 days
NIVORAPID – MAPEI
_______________________________
For thicknesses up to 20 mm
PLANIPATCH - MAPEI
_______________________________
For thicknesses up to 10 mm
