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| The stains and dyes
used to decorate overlay concrete penetrate, the surface
of the material, making them as durable as integral color.
A top coat of sealer enhances the color. Skilled applicators
can produce concrete floors that are indistinguishable
from stone, brick, tile, and slate. They can also create
murals or abstract patterns while maintaining the look
and texture of a monolithic pour. |
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Isolation
membrane. Unless you take
preventive measures, the cracks and control joints in the
existing slab will telegraph through the new polymer topping.
The overlay might hide them for a while, but they will eventually
show. When the existing slab has control joints, we cut new
ones at the corresponding locations in the polymer topping
or install a crack isolation membrane (NobleSeal CIS, Noble
Co., 800/878-5788, www.noblecompany.com). We use the membrane
when the location of existing control joints would interfere
with the decorative pattern, on the finished slab. Control
joints are still required, but the membrane allows you to
choose where to put them. We also use the membrane when an
otherwise sound substrate has a crack.
Primer.
Once the substrate is clean and dry, you need to apply a specified
primer or bonding agent. These materials can be brushed, rolled,
or sprayed onto the surface. With shotblasted or especially
porous concrete, we may have to use two coats. Polymer overlay
can be applied directly to the primed concrete substrate.
If a crack isolation membrane has been installed, it has to
be coated with the bonding agent.
Wood-ftamed
floors. Wood-framed floors have some give, so we always
inspect them carefully with an eye toward future problems.
Because the overlays are relatively light and flexible, most
floors that are framed to code are strong and stiff enough.
The subfloor should be of the required thickness and material
per the overlay manufacturer - usually 3/4-inch plywood. It
should be solidly nailed or screwed to the joists. Some manufacturers
recommend adding a layer of 1/2-inch plywood underlayment,
with staggered joints. We always use crack isolation membrane
on wood floors, with diamond lath nailed over it,
Mixing
and Applying Polymer Concrete
Like conventional concrete, polymer concrete is made by mixing
wet and dry ingredients. Some overlay products come bagged
in dry ready-mix form, with the polymer already in t he dry
ingredients - all you add is water. In other cases, the polymer
comes in a liquid form and is fieldmixed with water and typical
dry ingredients - cement and sand, as well as crushed stone
or aggregate when the overlay
is exceptionally thick. We use such a thick overlay when we're
leveling floors that are seriously out of whack. Some products
can be built up in layers, but it's easier to do a continuous
pour and put aggregate in the material that goes in the low
spots. This is possible because overlay is mixed on site in
small batches.
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