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One of the most troubling aspects of floor failures is the improper use of floor patch products.  These problems range from delamination of the patch to the substrate, powdering of the patch, tracking of rolling loads in the patch, and indentations into the patch.  The majority of these are caused because the person applying the patch put too much water into the mix.  When too much water is used in the mix water is non-compressible and where the excess water was after drying it will leave voids in the set product. (Photo 1)    The more voids in the set product, the weaker the product becomes.  Conversely, a floor patch mixed properly will be the high compressive strength it was intended to have. (Photo 2)

Let’s take a hard look at some of the techniques of using a floor patch:

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Substrates need to be free of residuals that will prevent a good bond of the floor patch to the substrate.  These include: concrete sealers, curing compounds and parting compounds, oils, waxes, silicones, soap, dirt residues, laitance or anything that might prevent a good bond. Shiny concrete should be roughened up in order to achieve a good mechanical bond. Photo 3 shows a case of hard trowel finished concrete with an over-watered patch and rolling loads.

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When should you use an additive?

Many installers use an additive for all circumstances, which is not necessary.  When you use an additive with floor patch you will give up compressive strength for flexural strength.  There is a time when that is necessary.  For instance, if you are going over a wood substrate, skim coating an adhesive residue or you are using the floor patch as an embossing leveler, this is where you need flexural strength.  If you are going over a concrete substrate you need to give up flexural strength for compressive strength.  Then the floor patch should be mixed with just plain water.  It would be alright to use the additive as a primer, but not in the mix.

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When should you use a primer?

The purpose of a primer is to enhance the bond to the substrate.  It will also stop the absorption of the mix water into the substrate, causing the floor patch to set too fast.  I feel this is why many installers add additional water to their floor patch so it will go further and not set up so fast.   Many times you can use just plain water as a primer.  It will wet-out then substrate stopping the rapid absorption of the substrate.  If you are on wood substrate, care must be taken not to over-wet the substrate. (Photo 4) 

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Substrate preparation

The norm is to buffer sand the substrate to remove and contaminates lumps and high spots. (Photo 5)

Thoroughly remove any debris from cracks or joints by digging the soil and debris out and using a vacuum to get it out of the void. (Photo 6)

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Mixing Procedure

The following is the procedure for properly mixing the floor patch to the already prepared substrate.

1. Use a clean plastic container

Mixing should be done in a clean container and NOT on the floor.  Many installers make the mistake of mixing their floor patch on the floor.  The reason for this is the floor patch is not mixed uniformly and many times the residue left behind is an area of bonding concern or failure. 

2. Add a measured amount of water to the container  (water goes in first)

Determine the floor patch manufacturers mix ratio and add the water first.  Adding the water first allows for a more thorough mixing of the floor patch.

3. Add a measured amount of floor patch powder to the water

Next add the powder to the water.  This too needs to be measured, remember the strength of the hardened product depends on the mix ratio of powder to water.

4. Use a drill motor to thoroughly mix the power and water together

Many installers tend to omit this process.  The whipping of the water and powder together breaks the surface tension of the water and actually thins out the mix. (Photo 7) 

5. Wet out or prime the area to be patched

As I indicate above, the wetting out or priming of the area to be patched stops the absorption of the substrate from absorbing the water in the mixed floor patch. (see Photo 4) 


When using a floor patch, it is important to monitor all of the temperatures to ensure that the patch performs properly.  Installers want a floor patch that sets up quickly, but in reality the slower a patch sets the better the integrity of the patch.  Temperatures play a huge role in this equation. Monitor the temperature of the powder, water, substrate and ambient room temperature.  You want them neither too cold nor too hot. Too cold retards the set and too hot accelerates the set.  Stay within the manufacturer’s recommendation for temperatures.

The preparation of substrates to receive any type of flooring materials is an arduous process.  Installers need to complete this task properly to give a proper foundation to the floor installation.