Quarter round molding doesn't get a lot of attention, but those tiny little strips along the bottom of your baseboard do serve an important function. While most people know this trim can cover unsightly gaps along the floor, they may not know that installing quarter round can actually save you money!
Any gaps along your exterior walls will allow cold air to come into your home. This often happens when two different materials line up, such as your floor and walls. Check your baseboards to see if you have quarter round installed and if not, look for gaps where they meet up with your floor. For gaps 1/4" and under, simply installing quarter round will help seal the area and prevent drafts. If the gaps are bigger than 1/4," I would recommend filling them with a spray foam first. You can buy a small can at most hardware stores and do this yourself—just remember that it expands, so don't over spray an area! When it sets, use a utility knife to cut the foam flat.
Choosing a Style
Quarter round looks like it sounds: imagine a round wooden dowel cut into four quarters. It can cover up to 3/4" gaps, but is available in smaller sizes. Measure the widest gap you see between the floor and baseboard and make sure you buy trim that will cover it. A good rule of thumb is to have something that is at least 1/8" bigger than the space you are covering. Shoe molding serves the same purpose, but is available in different styles if you don't like the look of quarter round. If you have straight or angled trim in your home, a linear shoe molding might look better.
You'll want to consider what kind of trim is already in your home and whether you should stain or paint your new additions. If the baseboards are stained, then you'll have to match the color and possibly the grain as well if it's a particular kind of wood. If you have any extra trim lying around, take that into a paint store and see if they can help you find the right color and grain to work with. You'll want to stain the molding before you install it.
If your trim is painted, you can buy primed MDF or pine. Expensive hardwoods like oak or maple aren't normally painted, but if yours are then I would recommend buying finger-jointed pine as it's a lower cost alternative to buying hardwood and then painting over it anyway. MDF can be even cheaper, but may not last as long as it's an engineered wood. (Remember that "white" comes in different shades, so getting a paint chip from the trim you are matching is ideal in order to color match perfectly.) Pre-primed trim can save you some time in the long run.
Once your molding is picked out, it's time to install! Measure the length of your baseboards in feet and add 15 percent to the amount when purchasing at the hardware store. Start in one corner and work left to right. I tend to work within one section and write down a few measurements as I go. Cut a 45 degree angle for the corner pieces, unless your walls are not right angles. If that is the case, you will need to figure out the appropriate angle. Remember to mark your trim and cut from the long point to short point for angles. I place an "S" or "C" next to my numbers to indicate whether I am going from a straight or corner cut. A straight cut will be used when butting up to door trim, or you might use a return angle to finish off a run if you like that look better.
You can use a miter saw or a miter box to cut the trim—it just depends on your experience with power tools. (The box is substantially less expensive to purchase than a power saw.) To install your pieces, use either a compressor and brad nail gun or hammer and finishing nails. The brad nailer will make the job go a lot faster, but if you don't have it already, a hammer is just fine for a DIY application. Choose finishing nails that are long enough to secure your molding in place. Normally 3/4" or 1" nails will suffice. Brad nailers use 18-gauge "brads" and the same length can be used. Nail into the body of the trim every 12 inches, and in smaller areas at least one at each end. Nail in one piece at a time, making sure the second will line up properly before continuing. Always aim for a snug fit that doesn't bow. Cut pieces a little long for your first few attempts to get a feel for it.
Once the area is properly trimmed, there will be a few finishing touches to tackle. If painting, you can fill the holes with spackle. I use painter's caulk to cover the thin space where the baseboard and quarter round meet. For stained trim, you'll need to find a product to fill the holes that will match the stain color you've used. I wouldn't recommend caulking at all between the baseboard and molding as it doesn't finish well. If there are large gaps, add a few more nails to get a tighter seal between the two pieces of wood instead.
Installing quarter round is a DIY project that you can tackle on a weekend. It may end up adding aesthetic value to the look of your baseboard, but it's guaranteed that sealing up the gaps will help you save on heating bills when cold weather comes around.