There are several reasons as to why you might see ugly cracks and holes appearing in plaster walls. Plaster walls look magnificent when new, but with age it requires a fair bit of touching up so that your house keeps looking stunningly beautiful. As architects would put it, while the house settles down on its foundation, cracks start to become visible on plastered walls. However, before getting on with the repair, let us try to understand why your walls develop cracks in the very first place. Reasons for Cracks on Plaster Walls It is of ultimate importance that you find out the exact reason behind the visible cracks as otherwise a deep-rooted and unattended problem will make the cracks recurrent no matter how many times you bring yourself to repair them. Here are some factors that could be the culprit behind your damaged walls.

• It is a known fact that wood absorbs moisture and inflates and contracts seasonally. So, the wooden frames of doors and windows in your house are no different. But plaster is not absorptive and neither expands nor contracts. So, if the minimum space between your wooden frames and plastered walls is not left, the plaster will crack with the repeated movement of the wood. Plaster on wooden walls also suffer the same fate.
• With time, the tension that holds the house together is also gradually released. As a result, cracks start to appear on walls with the growing age of the walls. Also, there are active gravitational forces, foundation motilities, as well as soil shifts that can lead to the walls showcasing cracks in them.
• Climatic factors also influence clefts to appear. Gales, humidity, drastic temperature alterations, change in soil consistency, dampness―they are all in some way or the other responsible for damaging your walls.
• Finally, occasional movement of very heavy furniture around the house or mounting of extremely heavy picture frames on a newly plastered wall, before it has set in well, can also lead to ugly scissures. Of course you may also damage a wall by accidentally hitting it hard with a piece of furniture or anything heavy for that matter.
• Lastly, your plaster will develop cracks if the builder does not keep the brick and cement walls well-moistened during the construction of the house. This is something I have noticed in my house. What happens is once the moisture dries out, the cracks start to rear their split faces. So, make sure that your walls are regularly watered while the house is still being made.

Now that we have a fair list of what could possibly plague the beauty of your plastered walls, let's get to repairing it. How to Repair Wall Plaster Small Holes For this you will have to purchase some spackle, which is a powder containing gypsum plaster and glue. When mixed with water this spackling compound forms a plastic paste. Do not use canned and premixed compounds as they do not last. Also, remember to mix only the amount you need as these compounds have a fixed period within which they dry up. So, if you mix more you will be wasting. Once you have this paste fill the tiny holes in the walls with these and then smoothen with a spatula. See to it that you make the surface absolutely plain. Allow this to dry for at least 12 hours. After this period you may notice that some spackling shrinkage has taken place and there's a slight dent in the places you filled yesterday. Apply a second helping of the spackle and make the surface even once more. Once it has dried up, scrape the area mildly with an emery paper and then apply primer and paint. Big Holes First vacuum the edges of the hole in the plaster so that all loose particles are removed. These particles can actually come in the way of the binding between the new patch and the wall. Now, make a plaster patch, in the shape of the gaping hole. See to it that the rims of both the hole and the patch fit into each other perfectly. Now, moisten the rim of the hollow, place the patching plaster onto the hole and use a spatula to cover the entire area with a spackling compound and smoothen the area. Allow it to dry for a day. The next day you may apply a coat of joint compound, and then dry the area again. You can smoothen the area with a sandpaper after that, and then apply primer and paint. Hairline Cracks To deal with wall plaster repair of hairline cracks, you need to first fill the cleft with a fine coat of spackling compound. Then on top of this you must place a drywall-reinforcing tape or a fiberglass mesh tape. The first tape variety is a better option and the repair job lasts quite long. The purpose of this tape is to buffer or shock absorb the pressure on the walls if the house is not on a stationary mode. Run a putty knife over this tape to smoothen it. Now, apply another thin coat of spackling and allow it to dry completely. Then reapply two more coats, but always allow the previous coat to dry first. Also, each coat should cover a little more area than the previous one. Then use an emery paper with a grit of 150 and make the area even, and then if you want apply primer and paint it up! Large Cracks and Loosened Plaster First take a 3/16" masonry drill with a carbide tip and drill holes into the plaster at an even gap of every 3 to 4 inches. Make sure that you do not drill through the wooden lath. The holes must be all over the wall wherever there's a crack. Now, remove the loose dust from these holes with a vacuum and then squirt some liquid conditioner into every hole. Make sure that you wipe away all the excess dripping conditioner from the wall and then fit a tube of a strong adhesive agent into a caulking gun. Now place the nozzle of the tube in every hole and pull the trigger fully in each hole. Next, screw in plaster rings into maximum number of tiny holes, with a drill driver. This will ensure that the plaster coat is absolutely clinging to the wooden lath again. Once you feel that the glue has dried up, take out all the plaster rings and even the area with an emery paper. Then apply a smooth coat of spackling compound on this, and let it stand unperturbed for 12 hours. Then you can use sandpaper on the area once more and apply a second finer coat of spackling compound on this. Paint if you wish after that. Knapped Plaster Corners For this you will have to do the usual dusting of the loose particles and then lightly moisten the corner with a sprayer. Next use a 6" spatula to fill up the crevice with spackling compound. Use a ruler to then make the filling level with the rest of the wall. Now, when the compound is semi-solid, moisten your finger to achieve the perfect angle in tandem with the rest of the wall. Of course, you must apply a second coat if you notice compound shrinkage on drying, but scrape the area first and then dampen the region a little before coating it again. In case you have a brick wall, then the crack could be deeper than the plaster. In such a case, remove the cracked plaster area. The bricks should be visible through it. Once you see the crack, use a coal chisel to create a slightly wider furrow. Then fill a grout bag with molder mix and fill the furrow with the mix. Finally, take a stick a painter uses to stir material and poke the mix into the furrow a little so that it sets better. Then scrape the area once the molder's dry and then accordingly plaster the area. So, you see, repairing plaster walls may be little messy, but it isn't difficult at all. Of course, you'll need to cover the surrounding walls and the floor with plastic sheets and tape them into position. Also, it would be safe to inform you that do not use a vacuum to clear the dust unless your vacuum filter is really fine. Otherwise the dust will reach the motor and ruin it. Use gloves, eye guards and masks to avoid suffocation or dust allergy. Interior painting plans should be executed once all repair work is over. It is understandable that the average cost to repair wall plaster will go down if you do the entire job alone. Professional help will make you shed out at least USD 400 to USD 700 depending on the wall plaster repair you get done, and the area that you live in. But a home job will cut the cost down drastically. So, what's keeping you? Hurry up! There are a lot of cracks to mend.