As the world of Residential Vinyl continues to evolve with more and more fiberglass backed floors, seam cutting procedures have basically remained the same. Whether it is a fiberglass-back, felt-back, or vinyl-back rotovinyl sheet floor, the seams of these products must be overlapped and double cut.
What still surprises me today is how many installers still are straight edge and butting seams. The straight edge and butt seam procedure was only intended for the Interflex or perimeter bonded products such as Armstrong Timespan or Mannington Gold. With the Interflex or perimeter bonded products, the straight edge and butt seaming method was required.
With these products, you had the ability to pull an open seam together with masking tape until the perimeter adhesive set up. These products were like rubber bands. They could be stretched and pulled where they needed to be, then they would tighten up.
With the fiberglass-back, felt-back, or vinyl-back products today, these flooring products to not have the capability to have an open seam pulled together, any fullness will not go away. If you do straight edge and butt the seams and try and close an pull together an open seam, you are creating fullness within the product and at some point and the seam will eventually fail.
When wet setting or installing dry to the touch, fiberglass-back, felt-back, or vinyl-back products, the seams should be double cut dry. If you double cut the seam with wet adhesive beneath it, when you remove the scrap piece of the seam, you are also removing the adhesive right at the most critical place of the installation, the seam.
I have researched the proper seam cutting method from many vinyl flooring manufacturers which I have listed below.
- Double-cut seams are generally used on heterogeneous products and felt-backed rotovinyl materials. These are materials which can be cut through two thickness in one cut. Install the first piece and bring the second piece into place in the room. It is best if the first piece has adhesive spread under the half along the wall to keep it in place. The seams will be cut dry (without adhesive under them), so the area approximately one or two feet back from the seams will not be spread with adhesive. The second piece is overlapped to the first one at the factory edge. If you are installing patterned goods, the overlap must be the correct amount so the pattern will match. Now secure the second piece by spreading adhesive under the half along the wall.
- Place a 2″ or 3″ wide piece of scrap under the seam area before the seam is cut. This will save the point of the knife when you cut through the two pieces of material and it will also produce a slight fullness to the seam. This is important because when the two edges are pulled back to finish spreading adhesive under the seam, the face can be compressed, causing the edges to be slightly apart when placed back into the adhesive. After the scrap is in place, put the straight-edge in place at the area where you want to cut the seam and cut through both pieces in one cut. Hold the knife straight up and down. If you are right handed, the scrap piece you are cutting off the top should be on your right hand side. After the adhesive is spread, roll the seam into place. After hand rolling seams into place, roll again with a 100-lb. roller. Apply appropriate seam treatments as recommended for the product being installed.
- The most accurate method for cutting seams in felt-backed and fiberglass-reinforced vinyl back products is double- cutting. When double cutting, both sheets are cut at the same time. This ensures the edges of both sheets are cut exactly the same, with no gaps or fullness. Many of today’s resilient flooring patterns feature very narrow grout or design lines. It is very difficult to align and cut these narrow lines in the exact center. Because the grout or design lines are often the focal point of the pattern, it is extremely important to maintain the exact width of these grout lines throughout the entire installation. The most accurate method of maintaining the line width is to make the seam cut along the side of the grout line.
- Cut the seam net, not full. Keep the knife blade parallel to the straightedge, at a 90° angle to the floor covering. Position the knife to allow as much of the cutting edge of the blade as possible to come in contact with the floor covering. It is difficult to keep the utility knife steady if only the point of the knife is riding on the floor.
- After adhesive is rolled on and completely dry position the flooring by over-lapping the seam edges. (Make sure to match pattern.)
- With a straight edge and a sharp utility knife, cut through both layers of flooring material (double-cut) at the designated match point. Make sure the utility knife blade is held in an upright position for a clean 90 degree cut.
- OVERLAP AND DOUBLE CUT SEAMING PROCEDURE
- This method of seam cutting is recommended for cutting seams in White Shield felt-backed products
- DO NOT USE THE STRAIGHTEDGE AND BUTT METHOD FOR SEAMING CONGOLEUM WHITE SHIELD FLOORS. THIS METHOD IS KNOWN TO CONTRIBUTE TO SEAM OPENINGS ON FELT-BACKED FLOORS.
- Overlap material for double cutting
- Seams are cut using the double-cut method only. Do not straight edge and butt seams. Once seam overlap is achieved, place strips of masking tape across the seam to prevent shifting.
Please remember, just because your installers says they have always straight edged and butted their seams, that does not make it the correct method. There is always a reason why manufacturers have certain recommendations.