Fixing Cracks In Walls Before Painting

Cracks can appear in walls for a number of reasons and can happen at any time. Most cracks appear due to natural movement in the structure. This is nothing unusual as all houses go through a settling in phase. The result of structural movement is cracks in the walls, thankfully “Fixing Cracked Walls” is a relatively simple process if you follow the steps below.

Step 1: Expose The Crack

Cracks in walls come in all shapes and sizes. The purpose of exposing a crack, meaning increasing the size of the cavity, allows for better adhesion to the filler. Fixing a very fine crack in a wall or ceiling can be difficult if the crack is not opened to allow for the filler to be pushed deep into the crack.

Bigger cracks already have a larger gap, but may have loose plaster surrounding the crack. All cracks should be scrapped, removing loose debris and creating a clear crevice for the filler.

You can use either a Stanley Knife or a Painters 12:1 Multi Tool to open up cracks in the walls or ceiling. Once the crack has been opened, use a Dusting Brush to remove dust and debris from the crack.

Step 2: Filling The Crack

This process depends very much on the depth of the crack with regards to what product or products you would use. For that reason I’m going to break down the explanation into two parts. First we will repair fine cracks in the plaster and then move onto filling deep gaps, holes and chases. Please note that some of the products below are for INTERIOR plaster repairs only.

How to repair fine cracks?

One of the best fillers that I have used consistently over the last few years is Toupret Interior Filler. Mixes effortlessly, drys fast and can be easily sanded to a professional finish ready to be painted. You don’t need to prime the filler before painting as it doesn’t flash.

How to repair deep cracks or holes?

The process of filling a deep crack is the same as above to an extent. If there is an actual hole in the wall, maybe from an electrical socket that is no longer required. Or a wall that has been chased for new cabling, these examples of deep gaps, holes cannot be filled with Toupret Interior Filler on its own.

I’ll use an example from a previous job where I tracked a wall to move a plug socket. Once the plug was moved and the electrical conduit was in place. I mixed up some Bostix Cementone General Purpose Cement, just add water and mix into a smooth consistency. Be careful not to add too much water, It should stick to your Flex Jointing Knife without sliding off.

The reason for using a ready mixed cement is 1) You don’t have to worry about mixing the correct ratios of sand to cement 2) Its inexpensive 3) Fills large gaps and holes with ease 4) Can be drilled once fully cured.

If for example you only have a one or two deep holes that need repaired and you don’t need 10kg of cement. Then another option is to purchase a ready mixed filler like, Ronseal Big Hole Filler. It comes in a handy 1.2 litre tub, ready mixed, simple to apply, dries fast, ideal for small repairs.

fixing cracked walls

Depending on the size of the repair you can use one of two products, Toupret Interior Filler or if you have a larger area that you need to plaster. Gyproc Easi-Fill is an excellent product for larger plaster repairs. Similar qualities to toupret, mixes easily, dries fast and sands easily.

Deep Gap Repair Tip

Leave your general purpose filler or big hole filler 3mm shy of the surface to allow for your finishing products, (Toupret or Easy-fill).

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What Tools Do I Need?

How To Fill Cracks In Plastered Walls

Now that you know what products and tools you require to repair either fine cracks or large holes. There is a process to successfully using both tools and products to achieve a professional finish.

1)  Always open fine cracks using your stanley knife or edge of your painters 12:1 tool. This allows the filler to be squeezed deep into the crack resulting in a permanent fix.
2)  Mix your filler firmer for large holes and soft for fine cracks.
3) Use your flex knives to compress the filler into the crack or hole. The larger flex knife is generally used to pass over the filled area smoothing out the compound so thats its relatively flush with the surrounding surface.
4) Large cracks, gaps and holes will need filled more than once. Don’t try to fill a large gap or hole in one go as the filler will sink when dry, wait until dry and fill the hole again.

How To Fill Cracks In Walls Before Painting

After the filler has dried, sand using 120 Grade Sandaper (medium), continue sanding until the edges of the surrounding surface start to show. Use the touch of your fingertips to test smoothness and for any bumps or unevenness. It helps to wrap the sandpaper around a Sanding Block or Hand Sander which 1) Saves the hands, especially if your sanding a large area 2) Helps to acquire an even finish (level), no bumps or raised areas.

If the plastered area is particularly rough with an excess amount of filler. Start by using a coarse Sandpaper 80 Grade (course) until nearly level, then move up the grade to 120 (medium). This will speed up the process of sanding by initially removing more material.

All sandpapers are graded. The reason for grading, is to help the consumer understand which sandpaper should be used for a particular surface, sandpapering grading explained. Simplified, the lower the number, the courser the sandpaper.

Painting Over Filler

In some cases depending on the product used, Toupret Interior Filler for instance, does not require priming before painting. Personally from experience if you are repainting a wall that has had plaster repairs, it is good practice to mist coat the fresh plaster.

Use a ratio of 60% contract matt to 40% water, allow to dry and then continue to paint as normal.

If your intending on wallpapering, dilute some wallpaper paste to a thin consistency and coat the wall. This will allow for better adhesion when hanging the wallpaper.

Fixing cracks in walls like a pro requires a combination of right tools, products and little patience.

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