In early houses every feature had a practical origin, and wide-board painted wood floors were no exception. The majority of floors were constructed of wood planks from 8" to 18" wide, because narrow boards were expensive to prepare in a pre-industrial era and therefore reserved for the best rooms. Though many wood floors were meant to be unfinished, care was also a practical concern and these boards were often painted to ease cleanup and protect the wood. Simple as they are, painted wood floors are historically significant parts of many old houses and they deserve good stewardship. With quality materials and proper preparation, you can revitalize your painted wood floors and preserve them for many years to come.
Preparation Is Everything
Restoring a painted wood floor is time-consuming, so be sure to set aside several days for completing the necessary steps and several more for your room to be off-limits to traffic. What is a week or two when a good paint job will last decades?
Floor work is a hands-and-knees endeavor, so invest in knee pads. Make sure you have proper equipment for personal protection too: gloves, safety glasses, a suitable dust or vapor mask, and a filtered vacuum. Methods for identifying lead paint hazards fall outside the scope of this article, but it is always a good idea to test painted surfaces in older buildings before disturbing them. Lead paint test kits are readily available and fairly inexpensive.
Floor preparation begins by going over the floor with a hammer and punch to set any nails or plugs that protrude above the surface. Next, address the gaps. Small gaps may merely be unsightly, but gaps wider than 1/4" can be a nuisance, catching shoe heels or pet paws. There is no way to reverse gaps caused by compression set (gaps caused by seasonal changes), but you can improve them by cleaning and filling. First remove built-up debris between the boards to the extent possible. Your objective is to remove all the junk along the sides and down in the gaps between the floor boards. Any tool that fits the gap will do. We use a linoleum knife that we have sharpened into a hook. Ready-made tools (such as the 3-in-1 tool from Hyde) work well, as does a screwdriver.
Keep a vacuum cleaner handy to pull out additional loose debris after you dig. This is an important—though unglamorous—step. The better you clean between the boards the better any fill-in repairs will hold and the longer your refinishing job will last.
Before repainting, you must sand the floor for best adhesion. You are not trying to remove the old paint layers, just give the surface "tooth." (You won't need to prime. Even on bare wood, most floor paints don't require primer.) We use a random-pattern orbital power sander that attaches directly to our HEPA-filter vacuum cleaner. However, you can use any power sander or even sand by hand. (We start with 60-grit paper, then go back with 80-grit, followed by 120-grit to remove any sanding marks.) Vacuum as you go and when you have completed sanding, continue to pay close attention to the gaps between boards.
Then thoroughly wash down the floor by hand with a big sponge and a cleaner that will remove old wax, grease, and general grime. We use TSP (trisodium phosphate), Spic 'n' Span, or Dirtex, and then rinse thoroughly with clean water.
Filling the Gaps
Filling large gaps prior to painting will protect your boards from the damage of future debris build-up, as well as make the floor much easier to clean. We have had success with a commercial caulking system used in many construction applications; it accommodates the floor movement while it fills and seals the gaps. We back the gap with a closed-cell foam backer rod that prevents three-point bonding, then caulk to fill and seal the edges of the gap. (We use products from Sonneborn, but there are many caulking systems available.)
The methods we use are best undertaken in fall and spring when the gaps are midcycle—that is, when the wood is neither at its maximum nor minimum dimension. Summer is a poor time to fill gaps because the wood is fully expanded.
First, pick a rod diameter that will fill your crack snugly without being forced into the space. Next, fill 2/3 of the depth of the crack with the foam backer rod, pushing it down firmly with a blunt tool that will not cut the foam. Then, wearing solvent-resistant Nitrile or PVC gloves, fill the remaining gap with a one-part urethane caulking (such as Sonolastic NP-1) until it is flush with the surface. You may want to mask the wood on each side of the gap with ultraviolet-resistant tape (such as 3M Long Mask) to make this step easier. Once you run the caulk, use a finger or scraper covered with a thinner-soaked rag to push the caulk into the gap. (You use thinner because urethane caulks set up with water.) You can fill any split boards in your floor at this time.
Remove any excess from the wood surface with a thinner-soaked rag. Caulk left on the floor becomes sandwiched between the wood and paint and will move independently, causing the paint to crack. It is fine to paint over the caulk between the boards.
Properly applied, the caulk will move with the wood. The correct caulk will not adhere to the backer rod, so it is not as likely to crack from the dimensional stress of a three-point bond. The better you cleaned out the debris along the sides of the boards and inside the crack, the better your caulk adhesion will be. Over time, the caulk may split some, but this flexible filling is still better than hard debris that can damage your boards. If you use caulk that is close in color to your paint any cracking will be less visible. Otherwise opt for black, the least obvious color.
At this point leave your floor alone for a couple of days to allow the caulk to completely set up. It will still be soft, so be careful where you turn your feet or place your knees. We usually damp-sponge rinse the floor one more time now to remove additional dirt and lint and encourage the caulk to set up.
The Painting Process
Now you are ready for paint. When it comes to deciding between oil-based paint and water-based (latex) paint, generally we prefer oil for any high-traffic areas and most woodwork. When you consider that a floor is probably the most demanding surface for paint, the extra work and wait required for oil-based paint is worth it. All floor paints have an exceptionally glossy sheen because they are formulated with resins that set up harder than regular paint for additional durability. (There are latex floor paints, some with cross-link activators, which we have only used in low-traffic areas.) A good neighborhood specialty-paint store is invaluable to help you understand the paint brand options.
Wear soft clothing, socks only (no shoes), and an organic-vapor charcoal mask (different from a HEPA filter mask). Always have handy a rag with thinner on it and a vacuum cleaner because there will be lint and dust that magically appear. You can create your own tack cloth for picking up lint as you go along by putting just enough floor paint and thinner on a rag to make it sticky. We use a roll-and-brush technique to apply paint because a roller helps put down the paint evenly, and brushing offers a nice finish appropriate for older buildings. Two coats of paint will be necessary.
First edge around the room and any pipes, radiators, and other floor penetrations using a brush-size you can control. Begin rolling from one edge, on one board, working in as far as your natural reach. We prefer to use a 4" foam roller (because it leaves no lint), and a 3"- to 4"-wide china bristle brush. A wider brush fatigues your hand faster, but it requires fewer strokes, so brush width is a matter of personal preference. You want to lay down enough paint so that your brush moves smoothly without "chattering" (skipping), but not so much that it floats on top of a puddle of wet paint (painting the puddle).
It is best to paint one board at a time; two to three boards are okay for a more experienced painter. Remember, you can't go back to a board once you have left it if you want a smooth, lapless job. If you try to fix an error once the paint has set up (within only a few minutes), the sheen will show an obvious mark.
Allow several days for this coat to set up, then lightly scuff-sand the floor with 220-grit paper to take off any raised grain or foreign particles that may have shown up on the paint and to leave a good tooth for the next coat. Remember, the paint is still rubbery so don't be too aggressive! Gently vacuum and use your tack cloth to wipe the floor down again.
Afterward, apply the final coat using the same techniques as for the first coat. This final coat should set up for a good week, and it will take a month for two coats of oil paint to cure fully. During this time the floor can feel firm and dry, but it will still lift easily with a heel turn or while moving furniture. (We test paint softness by pushing a thumbnail into the paint in a room corner or other inconspicuous spot.) If you want to move back in, put your furniture on pads or casters and lay down paper for extra security while walking on your beautifully painted wood floor.