A random or light random machine polished concrete finish is typically a much better option than burnishing a floor.
Care needs to be taken not to confuse a burnished finish with polished concrete that has a light random (salt and pepper) finish. A burnished finish is achieved by cleaning and then sealing a well finished slab. It is important to understand that a burnished finish does not have the durability of polished concrete.
For a floor to be suitable for burnishing a mechanical, powered trowel (helicopter) is used repeatedly by the concreter to create a finish that renders with a level of sheen. Screed marks and footprints must be removed during the helicopter process before the concrete sets.
Uneven trowelling will result in an uneven floor. If the concreter leaves small dips or humps in the floor they will be highly visible in the finished floor. Similarly the slab must be trowelled as close to the edges as possible.
It must be stressed that slabs tend to have a darker centre and lighter edges. There is very little consistency in the finish. If the area to be burnished is large don't be surprised if the irregularities and inconsistencies are unappealing.
(View unappealing burnished floor photos)
The job of the concreter is to achieve an even finish with a level of sheen. This can pose a further problem with the choice of a sealer that can bond with the glossy concrete surface so careful consideration is required on the type of sealer specified.
Burnished floors are sealed at the end of the building process so can be susceptible to staining. If the floors have not been protected during building construction stains from spilt liquids or wet timber and sawdust can leech into the concrete. As no grinding is involved these stains will remain visible in the finished floor!
We have frequently been asked to inspect floors completed by other contractors who are in dispute with owners who are disappointed when their burnished floor fails to meet their expectations.
It is often the case that a floor grinded back to light random exposure and finished as polished concrete is a far more successful, durable and satisfying result for both the building contractor and end user.
The disappointment on the face of the new owner of a burnished floor can contrast dramatically with the happy face of the owner of a light random polished concrete floor. This type of finish usually looks more like the glossy photo of the light grey floor that inspired a burnished finish in the first place.
This is not to say that a suitable burnished floor for Industrial and Commercial applications cannot be achieved however it is always advised to employ a very experienced and dedicated concrete slab concractor. If a slab intended for a burnished finish has been trowelled impeccably the concrete polisher's job is then only to thoroughly clean, lightly buff and then coat the floor with either an oil based or acrylic sealer.
A burnished finish incurs fairly large costs from the concrete slab contractor as they do the bulk of the work to achieve the burnished finish so it is wise to make sure you understand what the end product may look like. There are many hundreds of variables in concrete colour variations, stains, helicopter and screed marks that are visible in a burnished floor. We are able to demonstrate a few types of variables one may encounter in a burnished floor in example installations we have on display in our showroom.
If a slab has not been meticulously finished by the concreter one might choose instead to finish the floor as a light random or full exposure polished concrete.
