We are just finishing up the terrazzo floors for a stunning waterfront home at Sax Point in Victoria, BC. The house is over 100 years old and has a questionable subfloor that needed serious repair. All the cracks were cut with a crack chasing blade and filled with a specialized structural repair urethane. Multiple layers of patch and levelling were performed to bring it up a flatness level adequate for terrazzo.
Floor Prep
Extensive floor preparation was need as the floor had multiple floor coverings and many cracks.
Terrazzo for Lunch
The aggregates were carefully weighed out so every bag had exactly the same amount.
Crack Control Check List:
1. The saw cuts must be a minimum of 25% of the depth of the concrete. If you cut less than 25% it will be only a decorative cut. Material design experts say to cut 1/4 the depth at a minimum.
2. The relief cuts must be done before The majority of shrinkage starts. This usually means cutting the slab a day and a half after the poor is been finished. If the pour was done on a Friday, cutting would ideally take place Saturday afternoon or Sunday morning. Cutting done to early can spall the concrete and leave saw cuts with chipped edges.
3. When cutting in floors that utilized in floor radiant heating, consideration must be made as to how deep to cut.
Everyone has their own opinion about cracks in concrete, some say they don’t mind them, most people despise them. Cracks can and will happen, it is our goal to minimize them as much as possible Shrinkage is a main cause of cracking in concrete slabs. As the concrete hardens and dries, it shrinks due to the evaporation of excess mixing water. The wetter or soupier the concrete mix, the greater the shrinkage will be and the greater the likelihood for cracks to develop.
Using concrete with a low water-cement ratio and not adding excess water at the Jobsite will help to keep shrinkage in check.
There is virtually unlimited options for integrating glass, metals or specialty stone into a concrete floor.. How the glass is applied, the quantities of glass used, and the mixes of colors chosen can provide a unique and signatured decorative concrete product for those up to the challenge.
The most common applications of integrating these specialty materials in decorative concrete are (1) seeding and (2) mixing integrally. First, the seeding concept:
Seeding glass means sprinkling, broadcasting, or spreading glass onto the surface of a concrete floor, slab, or other surface. The advantage of seeding glass is that the quantity of glass used is reduced relative to other methods. Also, you can continue to use a traditional 6-bag or other traditional concrete mix that you’re used to and simply add the glass as a decorative accent to your project surface. The disadvantage to seeding is that it’s tricky to uniformly spread the glass on your concrete surface.
The second most common application is integral mixing. Integral mixing means replacing all or a portion of the aggregate in a concrete mixture with recycled glass chips. If you have your own proprietary mixture, simply subtract your original aggregate (pea gravel) amounts by weight by the amount of glass added to your mixture. The advantage of mixing integrally is that the glass aggregate mixes uniformly in the batch of concrete and is obviously uniformly segregated in the finished concrete product. The disadvantage is that much more glass is needed in a batch of concrete relative to seeding/broadcasting.
Use your imagination, the concrete floor is your canvas.
Sub Heading
Decorative cuts can be routered into any concrete floor. Currently, the trends are towards minimalist open floor plans with restrained patterning, although borders, or grid patterns can be helpful when a floor has bad staining, many patches or undesirable areas. Breaking up the surface with a geometric, or grid pattern will draw the eye away from potentially unsightly imperfections. When refinishing floors previously installed with carpet, tack strips around the edges usually spall the concrete and need to be patched. A border around the edge can take care of these areas that may stand out in a finished floor. Cuts can be a great way to distinguish areas, create tactile strips at stair landings and provide colour separation.
Refinishing your basement?
Have low ceilings? Moisture issues? Have dogs? Tenants that trash your floors? Hot water tank flood? Concrete breathes and may be the right flooring for your basement.
Stone Design has started polishing the floors of the Crag X climbing gym on Pandora Street. This stunning architectural space was left with a garage floor finish and the management decided it was time for an upgrade. As avid climbers, Stone Design brought in a bunch of climbers friends and got to work after hours to bring the floor up to a level of the architectural space around it. This process will be a multi phase process, starting with the front entrance. During phase 2 the original bad patches will be cut out and repaired, and the control joints will be addressed. Phase one involved a light cream polish to remove staining, and the cure and seal that was put on at time of placing the concrete. The wet polish was taken to 100 grit and a concrete densifier was applied. From here we polished to 800 grit and sealed the floor.
We are proud to be well under way on the floor for Victoria’s hottest new restaurant – the Boom + Batten. Victoria Stone Design worked with the Farmer Construction concrete finishing crew to seed the water front slab with specialty granite and glass aggregate.
A black integral colour was added to the 28 MPA concrete. One yard of green 1″ BC granite aggregate, combined with #3 black glass was added to seeded into the concrete slab after it was bull floated. A Squamish aggregate provider batched a special band of stone that the author came across when climbing the chief recently.
This West Coast contemporary home showcases charcoal polished concrete floors. Only resin diamonds were utilized for a “cream polish”, as the homeowner wanted the floor to be as dark and rich as possible. It was poured on a plywood t&g base at 2″ thick and had minimal cracking. The slab was placed with integral charcoal pigment and power troweled incredibly smooth. By starting with the right diamonds, the patina and colour was retained, and small imperfections removed.
It is not surprising that the popularity of polished concrete for residential floors has grown in conjunction with advancements of in-floor heating technology.
Conventional underfloor heating systems use either electrical resistance elements (electric systems) or liquid flowing in pipes (hydronic systems) to heat the floor. Both types can be installed as primary heating systems or as localized floor heating for thermal comfort. Polished concrete can be integrated with both hydronic and electric heating systems.
With over 20 years experience with SD Concrete as both a designer and floor installer, I have been involved in over 300 residential concrete floor installations. I have seen many installation methods, some with better results than others.
Hydronic systems and the complex heating systems that work with them are usually installed in new construction. They are generally not a good choice for renovations.
pumping SCC concrete over hydronic system
Renovations of kitchens and bathrooms are usually to refresh and renew, they do not typically include heating system overhauls. This is why electric heating systems have been so popular with renovation contractors and home owners in the past ten years. There is a big difference in overall floor thickness with each system. Typically hydronic systems utilize conventional concrete at an average thickness of 1.5” – 6” whereas electric systems use self levelling concrete mixes, and have a total thickness (including heating) of 3/4” – 1”. There is no ‘one fits all’ solution. When choosing heated concrete flooring systems, one needs to consider: insulation and performance, energy efficiency, weight of materials, and overall costs of both the floor finish and heating system.
HYDRONIC HEATING SYSTEMS
Hydronic heating is ideal for homeowners that do not like forced air heating, and want to keep their home at a consistent, comfortable temperature. Hydronic systems can use a single source or combination of energy sources to help manage energy costs. Heat pumps or solar panels can be integrated into these systems to help save energy costs. Excluding the cost of the concrete (which is a necessity of the in-floor heating system), polished concrete typically ranges from $5 – $10 per sq/ft.
Process with slab on grade
hydronic heating layers
level grade
6 mil vapour barrier
2” xps foam
rebar / mesh
pex tubing
concrete pour – 1.5” – 6”
hydronic advantages
standard grey polished concrete
cost effective for new builds when it is integrated into the heating system in the planning stages.
if a concrete slab is to be used in the construction, the concrete is already built into the budget.
extra thermal mass of the concrete slab helps with energy efficiency.
improved air quality compared to forced air.
SCC (self consolidating mixes) can be utilized where placement/ access is difficult.
hydronic disadvantages
initial costs for the system can be significant.
not efficient for small renovations.
using it for intermittent heating is not efficient. The system is designed to run at a constant temperature.
takes up to 7 hours to warm up when first turned ON.
Polished concrete aesthetics for hydronic systems
Conventional concrete is typically poured at a 4″-6” thickness for hydronic applications. The concrete can be poured as a monolithic pour, or done as two separate slabs, one to encapsulate the heating system, the other as the finished flooring. Both methods have their advantages and disadvantages, consideration to construction process and schedule will likely determine the best process for your project.
Integral color
1/2 white 1/2 grey portland cement with terrazzo
White or grey portland concrete can be utilized for the cement base color. White portland cement only comes in bags in the pacific northwest, and can double or triple the cost of the finished product. Titanium Dioxide can also be used to lighten the color of the concrete, it too is quite costly. Integrally coloring concrete to a darker or warm shade is quite simple, Davis Colors , or Interstar, both have great color charts and cost effective products.
Seeding the slab
glass cast into tru self levelling
Freshly placed concrete can be seeded with glass, stones, steel fillings or pretty much any hard material. They seeded materials are then floated into the surface and revealed through the grinding and polishing process.
Topical coloring can be done after the slab has cured and during the polishing process. These dyes penetrate into the concrete pores and are further protected with densifiers. This is not a process that wears off with time.
If you want to heat a small zoned space like a single bedroom or bathroom, electric in-floor heating can be a great choice. These heated floors are powered by electric cables or mattes of electrically conductive plastic built in to the floor. Electric mattes or cables integrate well with homes that use forced air heating. When going over top of plywood sub floors, membranes are essential to control cracking in the polished concrete overlay.
There is very little information available related to concrete overlays and electric heating systems. Search terms such as: heated concrete overlays, self levelling heated floors, embedding electric heating in polished concrete overlays, and thin heated concrete floors yield pretty much useless information to date (currently Feb 2017).
Calls to the large manufacturers: Mapei, Rapid Set, and Ardex didn’t produce any useful information. Using self levelling concrete to cover heating cables is far from a new concept, using it as a finished polished concrete floor with electric matt systems is where there is a lack of information. To date, Stone Design has completed 8 projects of various types and sizes that integrate electric heating systems and polished concrete overlays. These have been some of our most stunning and near perfect floors to date.
costs – $10 – $16 per sq/ft
electric heating advantages
can go over plywood sub floors. great for renovations.
nuheat cables ready to be covered
small areas (100 sq/ft+) can be done reasonably efficiently.
head room – max 3/4″ total thickness with integral heating system.
no special considerations for structural load.
minimalist aesthetic.
quick turn around – can be polished in 12-24 hours.
self levelling products are expensive. when encapsulating heating cables, thicker pours are needed.
floor prep for wood substrates requires an epoxy and/ or anti fracture membrane.
aesthetic options with electric systems
Heated polished concrete floors tend to fit aesthetically with most natural materials. The base ingredients (cement, sand, and aggregate), are found in nature and do well surrounded by similar materials. This means that modern homes, and their simplistic minimalist design are often complimented by polished concrete. Most engineered self- levelling concrete products contain very little aggregate, so grinding further into the slab does not mean larger aggregate. Polished self-levelling floors are usually more consistent and uniform when compared to conventional concrete. A cream finish aesthetic, without the busy look of sand and aggregate is much easier to achieve with self levelling products. Many customers ask about white or cream colored floors, achieving these aesthetics are completely possible with concrete overlays.
Polished concrete is a natural integration of design and function. In floor heating necessitates encapsulation of the heating elements, why not use this as the finished surface, and forgo adding more materials to the substrate?
