Your contractor will sweep or scrub the concrete first with a dry brush, and then clean it thoroughly with trisodium phosphate (TSP) and warm water, then let it dry. TSP is a mostly alkaline solution that does a great job cleaning grease and oil off concrete surfaces. Brush painting concrete siding costs $138 per 100 sq. ft., roll painting costs $50 per 100 sq. ft., and spray painting $32 per 100 sq. ft.
After you have done the multiplication, subtract about 40 sq feet per window, and about 60 sq feet per door. Divide by 400 (interior paint covers 400 sq feet per gallon). The number that remains, is how many gallons you will need. If doing multiple wall colors, then you should do this process for each room (or sets of rooms) with a particular color. 
A gallon of paint costs $15 to $40 and covers about 350 square feet with one coat. Designer varieties can run over $100 per gallon. Your contractor pays 50 percent less than what it runs in a home improvement store. You’ll also need to spend another $20 to $100 on supplies like brushes, rollers, masking paper and plastic. A professional will have these items on-hand.
Give your fireplace mantle an accent paint color, as this adds a quick update without having to tear anything out. In the kitchen, give your cabinets a new look with a douse of kitchen cabinet paint for an affordable and satisfying update. Countertop paint makes kitchen countertops look new again. You can do it yourself with a countertop paint kit in less than a weekend. A worn-out bathtub can look new with a coating of bathtub paint. Even your tiles can get a refresh or touch up, try tile paint on your backsplash or shower. Pro-tip: Use semi-gloss paint for kitchens and bathrooms as they wipe down easily.
The following guidelines will set you up for success. First, start at the top and work down. Second, paint out of the sun’s glare, since the sun will cause the paint to dry too quickly and flake or blister. To avoid marks, try to brush from one wet surface onto another. If you do have to paint onto a dry surface, overlap the wet paint onto the dry surface by several inches.
For trim and doors, start with 1 gallon (3.8 L) of trim paint for every 600 sq feet of floor space. Purchase more at the store if/when needed. Trim is something that is difficult to calculate exactly, and it is more time-efficient to simply start with less than you need, and go buy more after you have used up the first round of paint and determined how much you will need to finish by seeing how much you have painted so far, compared to the gallons used.
Prepping a house costs anywhere from $0.50 to $2.50 per square foot. This is almost always included in the total project price. However, the DIYer might negotiate some discounts for completing this work on their own. Be warned, proper prep is key to the quality and durability of the finish. If you do this work yourself, the contractor might no guarantee to finished product.
Begin prepping your walls by removing any outlet covers or lighting fixtures (if possible). Next, inspect your walls for any defects. If you encounter cracks, dents, or holes in your walls, simply fill them in with caulk or spackling compound. There are also a number of DIY tips to fill nail holes. Once your repairs dry, smooth them down with sandpaper and wipe the walls down with a damp sponge.
Carefully consider the gloss level. The shiny gloss paints are easy to clean, but will make any wall blemish stand out. The flat paints will help disguise wall blemishes, but can be difficult to clean. Generally, you'll want glossier paints where there's lots of steam or cooking (baths and kitchens) and in high-traffic areas. Flatter paints are preferred for large walls and ceilings.
Do the cleanup. When the painting is done, send the painter home and do the cleanup work yourself. This will include rolling up drop cloths and collecting scrapings, removing painter's tape (use a hair dryer on low heat to soften the adhesive), cleaning paint brushes, rollers, and other tools, replacing electric switch plates, outlet covers, and light fixtures, and sealing any leftover paint cans and storing them in a dry, temperature-controlled location.
The Cutters. Someone with meticulous attention to detail and a steady hand should be assigned the job of "cutting in," or painting a straight edge where needed, such as along a wall where the ceiling does not get painted. Many products are available to assist, but none work as well as a person who's good at doing it freehand. Ensure this person is skilled (ask them to show you). A poor, jagged, wavy or splotched cutting-in job will jump out at you every time you walk by it. Why more than one cutter? This job is nerve-wracking and painful to hands and arms after a few days. You'll want to give this person a break after a few walls.
You might pay an additional $1 to $5 per square foot for optional repairs and updates. Consider having your molding, trim and baseboards checked while you have a professional in your home. This might be a good time to upgrade or repair any cracks, warps or other issues. Pros can usually touch up or replace these items for an affordable rate, and they may even package such fixups with your project.
Whether you decide to do the preparation work yourself or have a professional do it as part of your project, proper preparation makes all the difference in creating a smooth and lasting finish. Do it correctly the first time or you’ll quickly end up spending more to fix peeling and chipping paint. Follow this process before starting on your home's exterior. Keep in mind that the process may vary based on your siding materials:
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