| Floor Finishes |
Concrete floors are surfaced with a wide
range of materials, these include tiles , terrazzo, magnesium oxy chloride
, granolithic and cement/sand
finishes.
Granolithic and sand / cement floor finishes are laid in-situ
in one of four ways:
Monolithic , Separate, Unbonded and floating.
Monolithic construction is where the topping coat is placed on top of the
still green concrete base, this has to be done within three hours of the
laying of the concrete base so that the concrete and the topping set together
to form a perfect bond .
In this type of floor construction the average
thickness of the topping coat should be about 15mm and the size of
the bays can be up to 24 sq. meters.
Separate construction is where the topping
surface is laid on a hardened concrete base
in such a way as to obtain the maximum possible bond .
In this type of floor construction the thickness of the topping coat should
be on average 40mm when the concrete base has been hand hacked
, and bays can be laid up to 14 sq. meters.
If the concrete base has been mechanically hacked the thickness can be reduced
to 25mm and bay sizes can be increased to 16 sq. meters.
Unbonded construction is when it is inadvisable
to try to bond the topping with the existing concrete . There are many
reasons why a good bond cannot
be achieved , among these are that the floor may be to old , the concrete
may be covered with oil or grease, or the concrete may be suspended and
movement may occur .
In such cases the new topping coat should be completely
separated from the concrete base by covering this surface with a waterproof
membrane . This type of topping coat needs to be at least 75mm
thick to resist loading stresses , the maximum size of the bays should
be limited to 9 sq. meters.
Floating floor construction is where a
resilient quilt of 25mm thickness is laid with butt joints and turned up
at the edges against the abutment
walls the screed being laid directly over the quilt.
The main objective
of this form of floor screed is to improve the sound insulation properties
of the floor. In this type of floor construction the topping coat should
be on average 65mm thick.
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| Floor History |
Up to the nineteenth century the ground floors of most small
buildings were formed directly off the ground, the soil being rammed until
it was
firm and on it were laid flagstones or bricks to form a hard surface.
This sort of floor was unsatisfactory, because the moisture which was
continuously withdrawn from the soil below the building made the floor
damp and cold, and a great deal of heat was required to dry out the
damp air in the ground floor rooms.
During the nineteenth and early years
of the twentieth centuries, when many of the central town and city dwellings
were built, it was common practice to construct the ground floor of timber,
raised above the level of the ground inside the building. This type of
floor is called a raised ground floor and it's great advantage is that
the space between the raised timber ground floor, and the earth below,
prevents much dampness from rising to the floor above.
Because of the
unhealthy conditions in which many people lived, due to dampness from
floors formed directly off the ground, the first Model Health Byelaws,
1936, required all inhabited buildings, built after that date, to have
a continuous layer of concrete spread between the external walls of the
building to
prevent dampness rising from the ground into the building.
This layer
of concrete spread over the site of the building had to be 150mm.
Some years after the Second World War the acute shortage of timber in
this country, and later the sharp increase in building costs, made it either
impossible,
or at the best very expensive, to construct raised timber ground floors
and the solid ground floor came into common use.
This is a floor formed
directly off the site concrete which is surfaced with some hard, smooth,
attractive floor finish.
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