Sealing a seam in a vinyl floor is part of installing a new floor and also can be a good repair for a floor that was initially installed without seam sealer. If you are repairing an existing floor, it is important that you soften and flatten any curvature to the flooring before sealing the seam. The overall process, however, is not difficult with the proper tools and preparation.
Warm the edges of the vinyl with a hair dryer, making the vinyl more pliable.
Clean the subflooring under the seam to be sealed. This will allow a good bond between the floor cement and the subfloor.
Mask off the surface of the flooring. This will prevent any excess flooring cement from damaging the floor surface. Make sure the masking tape reaches the edge to be sealed.
Apply sheet floor adhesive, using a flooring paste spatula, to the flooring along the seam to be sealed. This will prevent the flooring from moving when sealing the seam.
Place books or other heavy objects along the seam. Use newspaper to protect the books from any cement that may seep up through the seam.
Once dried, remove the masking tape and apply seam sealant to the seam to fuse the vinyl. The exact procedure varies, depending on the sealant kit.
Be sure to line your seam with paper when adding books or other weight to the seam to assist in cement drying and curing. Talk with a home supply store about the type of seam sealing kit that is best for your type of vinyl floor. Not all seam sealers work with all floors.