TN 05.23 Tiling A Small External Patio & Ground Floor Terrace

There are five key elements to a successful installation
1. A fully dried, cured and rigid concrete base
2. A DPM in the assembly to protect from rising dampness
3. Protection of the building - i.e. falls away from the property and sealing/waterproofing the junction with the property
4. The correct choice of products
5. Weather conditions when fixing

CONCRETE OR CEMENT: SAND SCREED BASES

When tiling any external patio area, it is important to remember that the substrate can support the chosen finish and any static or dynamic loads applied to it i.e. concrete of suitable thickness.

Concrete should be cured and left for a minimum of 6 weeks before any finish is applied directly. A longer period will be required in poor drying conditions and colder temperatures. Where required apply a levelling cement; sand screed.

Before laying ceramic tiles or natural stone, new cement: sand screed should be covered and cured for 7 days followed by a further 14 days of continual air drying; a longer period may be necessary in poor drying conditions or seasonal effects.

Concrete and Cement: Sand Screeds shrink during the drying process which can cause cracks to appear. Tiles, therefore, may crack if the concrete and/ or screed is not allowed to dry out properly prior to installation.

1. DAMP PROOF MEMBRANE (DPM)

Direct to earth sub-floors must incorporate an effective DPM.

Check if there is a DPM incorporated within the existing concrete or screed base. If this is not the case, to offer protection to the tiling layer above, consideration should be given to the use of a surface DPM i.e. BAL DPM, applied in a two-coat application i.e. blinding the second coat of BAL DPM with suitable aggregate i.e. BAL SAND. This is to provide a mechanical key prior to applying the screed or tiling.

To allow direct fixing, the floor should have a surface tolerance of SR1 i.e. when a 2m straightedge is placed on any part of a floor, the gap below the straightedge should not exceed 3 mm. NB. For small localized repairs in limited areas of the concrete or screed floor, consideration may be given to the use of BAL XL FLOOR ONE, applied up to a maximum 25mm as a separate operation. Allow to dry prior to waterproofing and installing the tiles.

2. FALLS

Falls in sub-floors should be between 1:35 & 1:80
Water must always be encouraged away from buildings

To provide a smooth and flat surface prior to the commencement of tiling and to adjust floor levels, if required, consideration should be given to the application of an unbonded cement: sand screed. Unbonded screeds should be laid to falls i.e. minimum thickness of 50mm up to a maximum 70mm. A bonded cement; sand screed (25mm to 40mm thickness) may be considered to create falls, but only if there is a DPM incorporated within the concrete substrate.

BAL QUICKSET CEMENT, when used as a replacement for Portland cement will allow tiling to commence onto an unbonded cement: sand screed after a minimum of 48 hours or 4 hours for a BAL QUICKSET CEMENT bonded screed (minimum 3 weeks for all Portland cement: sand screeds).

3. PROTECTION - WATERPROOF TANKING
Check the suitability of any existing waterproof coverings to be used for tiling first.
To protect the floor substrate from penetration of water from above, consideration should be given to the use of BAL TANK-IT, a two-part cementitious waterproof tanking system, suitable for use in external areas.

4. TILE ADHESIVE

The sub-floor onto which it is intended to lay tiles must be sound and suitably stable for the purpose intended. The floor’s surface must be dry and clean. All efflorescence, laitance, dirt and any other barriers to adhesion should be completely removed using suitable mechanical methods.
To allow direct fixing, the floor should have a surface tolerance of SR1 i.e. when a 2m straightedge is placed on any part of a floor, the gap below the straightedge should not exceed 3mm.
The adhesive should be applied to the dry base in areas up to 1m².
Unless a waterproof tanking system is applied, for porous bases, a skim coat of adhesive should first be applied before combing the remaining adhesive while the skim coat is still wet.
- Any depressions (ribbed, keyed profiles, etc.) to the backs of tiles will be filled with adhesive.
N.B For large format tiles buttering the back of the tile with a thin coat of adhesive is recommended, ensuring that any indented back profiles are filled before placing the tile onto position on the adhesive bed.
- Tiles will be firmly pressed into position with a twisting/sliding action ensuring that as far as possible no voids are left beneath the tiles

Table 1: Adhesive Selections

* Use of BAL ADMIX AD1 may be considered to enhance bond strength, improve flexibility and reduce water absorption. (Dilute 1 part BAL ADMIX AD1: 3 parts water by volume).

5. GROUT

Before grouting all adhesive must have dried properly. Thicker beds of adhesive and lower temperatures will increase drying times.

Joints between the tiles which should be a minimum of 3mm may be filled using any of the following grouts (See Table 2 below):

Table 2: Grout Selections

In the case of dark coloured tiles which absorb heat, a cementitious based grout would contribute towards restraining the tiles/natural stone. This would then counteract against the anticipated increase in the amount of thermal and moisture movements. In this case consideration, should be given to the use of an elastic, neutral curing silicone based joint filler e.g. BAL MORTEC® SOFT between the tile/ stone joints.

6. MOVEMENT JOINTS

Movement joints will be required and should be incorporated as per British Standard BS 5385-3. These joints should be a minimum of 6mm cross section.
- Perimeter movement joints and upstands i.e. drain housings/perimeter walls may be filled with either BAL MICROMAX SEALANT or BAL MORTEC® SOFT sealant.
- Intermediate movement joints should be incorporated within the tile assembly at intervals not exceeding 3 m dependant on trafficking, and selection of tiling.
- Intermediate joints may need to be filled with either a) harder-wearing and more durable material, e.g. an epoxy polysulphide, or b) a suitable pre-formed strip.
- Note 2.5 m intervals are required for dark coloured tiles.
WATCHPOINTS
• A solid concrete base should be chosen which should be preferably mesh-reinforced. It may be possible to fix directly to the surface of the concrete if it is sufficiently flat and even. A levelling cement; sand screed laid to falls may be required.
• Ensure that all substrates can support the anticipated loading e.g. static load i.e. weight of tiling and the dynamic loading i.e. foot or wheeled traffic etc.
• Backgrounds, tiles, tile adhesives & grouts must be stable to changing weather conditions and thermal fluctuations, water penetration and frost.
• All materials selected should be water and frost resistant.
• Tile, Stone and Mosaics with any form of mesh backing or agglomerate stone including quartz are not recommended for use externally.
• Ensure suitability of any waterproof coverings to be used for tiling first i.e. BAL TANK-IT
• Falls in sub-floors should be between 1:35 & 1:80. Water must always be encouraged away from buildings
• Do not carry out work unless the temperature is above 5°C and rising. The temperature range for which tiling can be satisfactorily carried out with normal methods and materials is between 5°C to 25°C.
• Areas of potential water penetration should be protected. This is to prevent ingress from water/dirt/contamination.
• On large exposed ground floor terraces, it would be recommended to consider using a subsurface drainage system i.e. GUTJAHR at ≥ 10m².
• In line with The Tile Association (TTA) advice in the technical document Cleaning and Maintenance of wall and floor tiles; “The use of steam cleaners is not recommended as they can cause stresses of the tile which may result in adhesion failure”

• The use of excessive high-pressure jet washing could abrade the grouting material in the joints.

Please note that the success of external floor tiling will always depend upon ensuring that water can drain away free and effectively. Therefore, suitable precautions should be taken to ensure this happens, otherwise the longevity of tiling cannot be guaranteed.

Detailed instructions on the use of all products mentioned within this document can be found in the relevant data sheets and reference should be made to them for further information. All the BAL Technical Data Sheets and Material Safety Data Sheets can be downloaded from our Website, www.bal-adhesives.co.uk

TECHNICAL ADVISORY SERVICE
For free expert guidance on the use of BAL products, or any aspect of ceramic tiling with BAL products, contact the BAL TECHNICAL ADVISORY SERVICE on 01782 591120.

THE BAL 25 YEAR GUARANTEE
BAL products are supplied with a 25-year product guarantee. For further details and/or copies please contact the Company’s marketing department.

NOTE
The customer must verify the suitability of any information, opinion, recommendation or advice (“information”) provided by the Company for the particular application for which any goods are intended to be used and the Company accepts no liability (whether in contract, tort or otherwise) whatsoever for any loss, damage or expense arising from the misuse of any information it supplies, nor for the use of any information in or for applications which are unsuitable or inappropriate. Building Adhesives Ltd operates a continuous research and development programme and reserves the right to alter or to update information from time to time.

“Note: Any advice, opinion or information is given to assist the use of the Company’s products on the basis that the user will ensure its suitability for the application intended. In particular the Company cannot accept liability for loss or damage which may arise from incorrect use of its products or from poor workmanship. The Company operates a continuous research and development programme and reserves the right to update information without notice.”