First, check the height of the sub-floor. It should be consistent for both the new and old flooring. If it isn’t, you’ll need to either add or remove a layer or two of plywood. Keep in mind that it is extremely difficult and also more expensive to install hardwood flooring over a concrete sub-floor.
The profile, also known as the thickness, of the new wood floors should match that of the existing floors. Do err on buying planks that are thicker in order to accommodate for sanding down the floors at the end of this process.
A flooring professional can tell you the species and grade for your existing floor and make recommendations for the best match. Whether wood is rift, quarter or plain sawn will also make a difference.
Probably the simplest of all steps: Simply measure the width of a board from the existing floors. If your new flooring will run parallel to the existing planks, a slight difference in width may not be noticeable.
If your new hardwood boards are going to run in the same direction as the ones in your existing floors, consider using the weaving (also called lacing and threading) method to blend in new flooring. When weaving, you must use boards that are of the same width as existing ones and you will need to sand and refinish the affected existing boards. This is going to be a more labor-intensive process, and, thus, a costlier one. In order to weave in new boards, the seams of existing boards must be cut so that you can take out planks and replace them with new ones.
For the best match, you’ll need to strip the old flooring and finish both the old and new flooring at the same time. This is especially great for old hardwood floors that are due for a refinish. If this isn’t an option, you can stain the new boards to match the old ones. A flooring professional can mix a custom stain for you to ensure a seamless transition.
Although adding and matching new hardwood flooring is a labor-intensive task, the results are often well worth the effort.