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Designing Buildings for Polished Concrete

A Practical How-To from Holly Dumont

Designing Buildings for Polished Concrete:
 
 
The highest quality diamond ground and polished concrete floors in new structures do not occur by chance. Coordination, beginning during the schematic design phase and continuing through the development of the construction documents, must occur between the Architect, Polished Concrete Expert, Interior Designer and Structural Engineer. This collaboration must take place in order to successfully integrate the polished concrete deliverable into the design of the facility. The information in this document is provided to specifically support the development of construction documents when Polished Concrete floors of the highest quality are the desired end result.
 
Thickened Slabs:
Where ever possible always thicken the slab rather then providing foundations under heavy or load bearing walls when polished concrete is the end deliverable. This will ensure your polished floors will be blemish free at both faces of that wall. The concrete installer will not spend the time to bring the cream to the surface along foundation walls thus the area along said wall can not be polished. If the wall must have a traditional foundation; exterior load bearing walls for example, use a 6” stripe of epoxy paint along that wall at the dull area. This solution is inexpensive and aesthetically pleasing. As a surface finish the epoxy will not wear off as the 6” area along the face of a wall is too close to be a traffic zone - foot or vehicular.
 
Expansion Joint(s): 
During the schematic design phase the building envelope and structural grid are developed. At this time the Architect must know approximately where the expansion joint(s) will be in order to integrate Polished Concrete into the design of the facility. As the building design moves forward with more detail the location of expansion joint(s) must be identified and coordinated with the Architectural interior walls. These walls want to be designed to hide the expansion joint(s) in areas that will have Polished Concrete as finished floors. Areas of the facility that may have carpet or other floor finishes would be ideal to cover expansion joints. This understanding must occur early in the schematic design phase with the Design Architect, Structural Engineer, and Interior Designer.
 
Finish Schedule:
The finish schedule, located in the constriction documents, is another place for bidders to see Polished Concrete as a deliverable. A floor plan identifying the specific floor finishes; using shades of gray and cross hatching; is invaluable to the Owner, Owners rep and bidders, Structural Engineer and Architect. That drawing will be used to provide the basic outline of the proposed Polished Concrete area and provide the starting point for the Control Joint and Pour Sequencing plans. Get you Interior Designer involved early or have your Design Architect act as your lead Interior Designer.
 
Control Joints:
The structural documents will have a floor plan showing the slab(s) on grade and or on deck. These documents must coordinate with the Architectural drawings for wall locations to determine control joint placement. The Structural Engineer and the Architect must collaborate to create the control joint floor plan. The recommended rule of thumb “note” to be placed onto the structural floor plan is as follows: “The polishing contractor will determine and submit for approval the final control jointing pattern. The pattern shall result in rectangular panels with ratio of long side to short side not to exceed 1.5 to 1 ” Typically the contractor will use the plan provided. However, if they provide their own the Architect must check it against the wall layout to insure accuracy. For example, saw cuts 2” away from a wall are not desirable because the joint and or wall may not be plumb and straight making the mistake imposable to hide. Rule of thumb is to line your control joints up under you walls or several feet away just in case one or the other isn’t perfectly straight. Control joints at columns in an Administration type building are best brought up as close as possible and stopped. 
 
Pour Sequencing:
The construction documents must also include a drawing showing recommended pour sequencing for polished and non polished concrete areas. This document breaks up the concrete floor into zones with shades of gray and cross hatching defining recommended pours. The Architectural walls and control joint pattern are used as a guide. The Architectural walls will sit on these cold joints hiding them from view where ever possible. If this document is not provided the risk of cold joints running down the middle of an exposed polished area exists. If your company or firm requires a pre-pour coordination meeting, as defined in your Project Manual “front end” or “boiler plate” contract documents, you may provide this drawing at that time rather then as part of the construction document bid pack.
 
Un- Polished Slab Areas:
Be sure and identify slab areas on the structural floor plan that are not to be ground and polished. On the Pour Sequencing Plan identify these areas as first pours. They need to be poured and cured out earlier as they will be used for staging tools and equipment throughout the project. Once the remainder of the concrete floor is diamond ground and polished no tools or equipment will be stored on them– they are finished floors and must me treated as such.
 
Pre-Pour Meeting:
Another way of handling pour sequencing for Polished Concrete is during the pre-pour coordination meeting. If, in your “Project Manual” contract documents  or “front end” a requirement for a pre-pour meeting currently exists simply put a note on the structural floor plan requiring the coordination of floor slab pour sequencing with the Owner at the pre-pour meeting. Be sure the Owner or assigned Owners Representative has the pour sequencing drawing as defined in the “Pre-pour meeting” paragraph to present at said meeting.  If a Pre-Pour meeting is not currently required in your contract documents, adding it is highly recommended. The Construction Manager and or General Contractor, concrete provider(s), subcontractor(s) installing the concrete, Concrete Polishing provider and Owners Representative must discuss schedule, concrete delivery, mix design, pour sequencing requirements, specification requirements like FF & FL, testing requirements, placement methods, finish requirements, pure wet curing requirements, saw cutting & control joint pattern, diamond grind and polishing est. This pre pour meeting provides these represents the first and only opportunity they will have to sit down in one room together to discuss the project before work begins. It is the bridge for communication that supports the desired end deliverable- Polished Concrete floors of the highest quality.