Prep masonry surfaces for painting by removing all loose material with a stiff brush like a nylon-bristled scrub brush. If the masonry has been painted before, scrape off any peeling with a putty knife. Hose the surface down if possible, if you're inside and can't spray with a hose, use a shopvac to remove as much dust as possible. Prime any bare spots with a coat or two of latex or masonry primer and let it dry completely before applying the finish coating.
Let new masonry cure for at least 30 days before coating it with any sealers or paint. This will give it time to dry out sufficiently to ensure the new coating will bond well. To test for moisture tape a 2x2 foot piece of plastic over the new masonry and wait about 24 hours before removing it. If the surface under the plastic is darker than the surrounding concrete after this time then there is still too much moisture present and you should wait another two weeks or more until this test can be done without any significant change in the overall color.
Painting any masonry surface is difficult when trying to get good coverage. A bare surface is the toughest because it's so porous it sucks up every bit of moisture that comes in contact almost instantly and it will keep absorbing moisture until it is saturated. This can mean that a full roller of paint will not go very far and it requires many coats just to cover a few feet.
To make coverage easier try a few tricks, first, be sure you have a very thick roller, a nap of at least an inch will be needed to spread the paint into all the little pits and crevices. Use a latex coating and mist the surface with water just before applying it to make spreading easier. Plan to do two coats on bare masonry to catch all the missed spots rather than trying to cover every inch with the first coat. To improve coverage, a third coat will probably be necessary and will be essential to get a smooth, consistent finish.
Masonry is primarily susceptible to two problems: cracking and efflorescence. Efflorescence is the white powdery substance that bubbles up on surfaces like basement walls. It happens when moisture penetrates the wall, causing alkali in the portland cement to leaches out and deposit on the surface.
If moisture is a constant problem, that issue will have to be addressed before using this process for curing an efflorescence problem. Check downspouts and drains for the source of the water and repair the problem. If the ground slopes in toward the wall, mound it up so water will run away from the building.
To remove alkali efflorescence, use a weak solution of muriatic acid and water. Be very careful with the acid, it is very corrosive and will burn everything, including skin. Even a minor splash of the acid solution can do damage so wear long sleeves, gloves and eye protection. Use a nylon bristled brush to scrub very gently to minimize splashing.
Rinse the acid from the surface using lots of clean water. Watch the run-off; soak it up with absorbent rags and wipe all surfaces down well to prevent the acid from damaging things like adjacent metal surfaces, floors and vegetation. Most of the time this acid treatment will cure the efflorescence problem but if necessary, you may have to repeat the process a second time.
If you're going to deal with efflorescence on an interior surfaces where you don't want to use a dangerous acid, try using a strong vinegar solution in place of the muriatic acid. Boil a cup of vinegar down to a half cup. This will double the normal acid in the vinegar which may be effective on some efflorescence problems.
To paint the surface let the treated area dry well if you're using anything other than a water-based coating. Latex can go over a damp surface and in fact, the masonry should be a little damp to make painting easier and improve bonding.
To repair cracks in foundations, walls, slabs and walkways first be sure the movement that caused the crack has been stabilized. If the movement causing the crack is minimal, it may be possible to fill it with a concrete caulk that will move with the crack for a permanent seal. If the movement is more severe it may be necessary to reinforce the footer or foundation to stop movement. Multiple cracks are an indication of major problems with the stability of the structure and can't be repair with this process.
To repair cracks with mortar use a putty knife or screwdriver to scrape out all the loose material. Hose out the crack if possible, if not, use a shop vac or compressed air to remove all debris. Soak the crack completely using a spray bottle when working inside and a hose on exterior surfaces. Saturate the surface well just before applying the mortar patch. If a crack dries out before the mortar is applied, soak it again. You can't get it too wet but if it becomes too dry the new patch will not bond well.
Use a pre-mixed bag of mortar or mix your own using one part portland cement and three parts very fine sand. Use the finest sand you can get from your local home store to make your patching mortar bond well with the old masonry. Mix the cement and sand well first, and then add water to make a thick mud that holds its shape.
Use a putty knife to press the mortar into the crack starting a one end. Press mortar into the crack until it starts to ooze back out. Do this along the entire length of the crack and then go back to scrape off the excess. Finish the repair by applying a smooth coat of mortar to level the area out. As you work, keep the surface around the crack damp with a spray bottle of water. After the repair is completed keep the patch damp like this for about 3 days.
To repair damaged and crumbling stucco, make a compound of 1 part portland cement, 3 parts fine sand and enough water to make a thick paste. If you need to match the natural color of your existing stucco because it's not painted, look for a sand color that's comes close and vary the ratio slightly until you mix the color you want. To see the final color of your stucco mix you will have to let it dry completely which will take 24 hours or more, so you may want to mix a small amount of paste to start and let it dry before deciding on the right ratio of sand to cement to achieve the desired color.
Mix your stucco paste thick enough to stay on a vertical surface without sagging. If you make a mistake and make the paste too thin, mix more portland cement and sand together and then add it to the paste to thicken it. Once it is mixed the paste will be workable for about an hour.
To make stucco repairs remove all loose material from the damaged area using a putty knife or similar tool. Then use a stiff brush or broom to remove dust and wet the surface with a spray bottle or compression sprayer of water. Apply the stucco paste while the surface is wet and shape it to match the existing finish. As the new patch sets and cures keep it wet with the water sprayer soaking it 3 or 4 times a day for three days. This will prevent cracks from forming as it dries.
Replace bricks that have come loose on steps and other minor masonry structures with a pre-mixed mortar. If you don't have the original brick to replace, you should try to find one that closely matches or the difference may be distracting. If the structure you want to repair was build before the late 1800's, don't use modern mortar and bricks to repair it. Because modern masonry is much harder than the older version, the patch will crush the surrounding, older structure as it moves naturally over time. Also don't make repairs to older structures if freezing temperatures are likely for several days to keep ice crystals from forming.
Soak the replacement bricks in a bucket of water for a couple of hours before replacing them. This will encourage a strong, permanent bond with the new mortar. This is the most important thing you can do to make sure the replaced bricks stay put. If you're repairing an older structure, especially one with noticeably soft bricks, don't soak them as long or they may absorb excess water.
Also soak the wall where you're working using a spray bottle or a hose to soak the surface repeatedly. The more water you can get it to absorb the more likely the repair will be a success. If the replacement brick has old mortar on it use a cold chisel to chip it off, also clean mortar off the wall where you are replacing working. Soaking the brick in water overnight may help to loosen the mortar and make it easier to remove. Use a hammer and chisel blade joint knife to get as much of the old mortar off as possible. The more you can remove the better the repair results.
If you're working with a new structure, you can use a bag of pre-mixed mortar to make this repair. If you have an older structure built after the Civil War you can use a mortar mix of 1 part lime, 1 part portland cement and 6 parts sand. Mix the lime and cement before adding the sand. For structures older than 150 years or so, use a lime mortar for repairs to avoid damage to the original masonry. A general lime mortar mix is one part lime and 3 parts sand. After mixing your dry ingredients add water slowly and mix to get a mud that scoops easily and holds its shape.
Heap the mixed mortar onto the replacement brick and the wall, on all sides to get good coverage. Press the replacement into the mortar and shift it back and forth until it settles into it's original position. Scrape off the excess mortar as it oozes out. Use a flat screw driver or a mortar pointing tool to level the mortar joint to a little below the brick face. Wipe any mortar off the face with a wet rag of sponge before it sets. Be careful not to disturb the mortar between the bricks with the rag.
Lay all the missing bricks in this manner and let the mortar set for about 24 hours before touching it. If the replaced brick is on an incline and likely to sag, support it with a board or something else that will hold it in place until the mortar can set. Be careful not to disturb the repair while doing this.
There are a number of coating products made for masonry surfaces. These include alkali-resistant primers, sealers, waterproofers and floor paints. In addition to these specially made coatings, common latex paint is a suitable coating for concrete and brick walls.
Alkali-resistant primers are made using chlorinated rubber and are primarily used on surfaces that have a chronic problem with efflorescence.
Sealers are normally clear and are used to prevent staining, stop crumbling sand debris and to make cleaning the surface easier. The use of clear sealers is particularly helpful for interior, exposed brick walls where the look of the natural surface is enhanced while making the wall smooth and debris free.
Waterproofers are made by mixing portland cement with a latex paint base to create a thick coating that will block moisture from escaping. These coatings are used mostly on basement and exterior walls. When properly applied these waterproofers will bond with a surface preventing future blistering and peeling. Use two coats on bare masonry and keep the coating moist with a light spray of water for 2 days as it cures. These coatings should not be applied over previously painted surfaces.
These coatings are available in epoxies, urethanes, latexes, alkyds and rubber-based enamels. Of these, the epoxies are the most durable and resistant to abrasion and sub-surface moisture. Urethanes and alkyd-based coatings work well in garages and workshops that see a lot of traffic. For interior basement floors in living areas, latex floor paint will work fine.