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Polymer toppings cure quickly, which
is a major selling point when there's not much time to do
the job. Some of the products I use can support foot traffic
in 3 or 4 hours and develop compressive strengths of 3,000
psi in 3 hours, 6,000 psi in 24 hours. Overlay products come
in two types, trowelapplied and self-leveling. It's usually
more economical to use trowelapplied toppings: They generally
cost less up front, and unlike self-leveling products, they
can be applied in a thin even coat. It usually takes more
material to do a self-leveling overlay because the topping
might be 3/8 inch thick at one end of the room and 3/4 inch
thick at the other.
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| Spreading self-leveling
toppings (top) has to be done with care. It's important
to work out any air bubbles, but the material shouldn't
be touched once it starts to set. A gauge rake (above)
is a handy tool for spreading trowel-grade material. Adjusting
the wire bales on each end raises or lowers the blade,
making it easier to spread an even coat of material. |
Trowel-grade materials also have longer
working times; some can be stamped or textured before they
set. To maintain a consistent thickness, we spread the overlay
with a gauge rake or notched trowel. Afterward, we go over
it with a regular trowel to produce the texture and finish
we want. Some trowel-applied materials are referred to as
microtoppings because they can be applied in layers as thin
as 1/16 or even 1/32 inch.
Self-leveling overlays set up very quickly,
which makes them tricky to use. It takes some experience to
know when to stop spreading self-leveling overlay. The material
starts to set in 10 or 15 minutes, so you have to work fast
to maintain a wet edge as you work your way across the floor.
Spreading puts the material where you need it and removes
air bubbles that can cause imperfections. But you shouldn't
touch the surface after the polymer starts to set. If you
do, it leaves a mark that's hard to repair. If you do it right,
the floor will be dead flat and have a glossy sheen.
Self-leveling overlay is soupy
when it's wet, so you should make sure there are no leaks
or holes in the substrate. We recently missed a small nail
hole in a bathroom floor and ended up with a cone-shaped depression
where the overlay leaked out. We happened to be using a product
that's difficult to patch. The client was very particular,
so we ended up tearing out and redoing that part of the job.
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