Sealants – Post Laying

Sealants – Post Laying

Sealing on site prior to laying is the next best option to buying the stone pre-sealed by the
factory, although conditions will need to be right for the works to be carried out. Sealers need
to be applied under clean, dry conditions, ideally indoors, with sufficient space to unpack,
clean (by brushing) each slab, apply the sealant and store the sealed slabs on site, under cover,
for at least eight hours while the sealant dries.

Skill, care and assiduity are required to successfully apply sealant on site. The sides and
bottom of the slab should not be sealed. Sealing the sides may prevent the jointing compounds
from gripping the paving, and the slabs are likely to be compromised by working loose.
The slabs should not be laid until the sealant has properly dried.

If it is not possible to pre-seal the paving on site, but have to rely on sealing after laying, it
is important that the stone is as dry as possible, as any moisture remaining within the slab
will be sealed in. Similarly, any marks that remain after laying may also be sealed under
the treatment.

Sealant repels water, and will make cleaning operations more difficult once applied. If it is
necessary to clean dirty stone by vigorous scrubbing, another coat of sealant may be required
to protect the surface.

Patio sealants should not be applied when the temperatures are lower than 5 degrees, or above
35 degrees, so care should be taken to ensure the work is carried out on a clear, dry, warm
day, once the paving is completely moisture free. It becomes weather-proof after eight hours,
but avoid working if heavy rain is forecast. Even a light shower may require a second coat of
sealant once the weather improves – in which case, avoid creating any stains which may affect
the efficacy of the previous application.

If the paving shows signs of efflorescence, whereby salts migrate upwards through the stone,
avoid sealing until the phenomenon disappears, as the treatment will seal the salts in, leaving
white chalky marks on the surface of the slab.

Always follow the recommendations shown in the manufacturer’s instructions. They may
suggest leaving the sealing until three months or more from laying to sealing, as this will
allow for any efflorescence to have disappeared.

The more porous the paving involved, the more sealant will be required, so there are no
fixed rates of cover of application. Softer sandstones will absorb far more sealant than harder
stones, and experience will be your guide.

You will need certain equipment and protective items when applying sealants. These will
include personal protective equipment, namely gloves, face mask and safety glasses at a
minimum, cardboard or plastic sheeting to protect walls, windows, paintwork, plants and
other items that may be affected by the spray.

A suitable, clean, low-pressure sprayer and/or a set of suitable brushes will be required,
keeping all animals and children safely out of the way. Start from the furthest point away from
your exit to avoid walking in the finished working area. Wear clean shoes to prevent making
any marks if you are obliged to walk on newly treated areas.

Apply in two coats; the second when the first is touch dry. After a quarter of an hour (sooner if
dry) apply a second coat, which should also need fifteen minutes to dry. Always clean off any
excess sealant. Failure to do so may result in a sticky shiny mess, taking effort to remove.

If left too long, excess sealant will be almost impossible to remove. Once dry, the area may
be considered weather-proof after eight hours, and fully cured after thirty days. Therefore, it
is important that everybody concerned appreciates the time scales involved, and refrain from
too much activity for a month after applying the sealant.

The application of sealants will not prevent moss, lichen, weeds etc from appearing on
the paving, but will make their removal much easier.