How To Repair the Surface of a Concrete Wall to Repair Crumbling

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    One of our friends asks about a border fence that they have in their backyard made of concrete that they believe needs repair. The wall has been in place for some time and it seems that the previous home owner has painted it and an grown ivy against the wall so the current owner is wondering if they can complete a repair on their own to clean it up and stop it from deteriorating.

    On first look it may seem that this wall is damaged but consider what we have been told. The wall has been in place for many many years. It probably dates back before the 1960’s. Second it has been painted and as you can see the paint is discolored so the paint is old .. at least many years. and finally there has been enough time after the wall was painted for ivy to grow on it. This means that another 5 years or so passed between the time the wall was painted and the ivy grew to a height of 6 feet tall.

    So, when you consider these factors you can probably assume that the wall is in pretty good repair. It is not actively losing large chunks of concrete and the damage may not even be damage.

    When concrete is poured it is contained in forms. Many years ago these forms would have been made out of wood. Today they are aluminum. When the forms are set in place and filled with concrete they need to be vibrated so that voids and other textures that look like this wall don’t happen. This texture may not even be damage but if there are signs of deterioration the wall seems to be structurally sound. There are no large chunks or cracks at this point.


    Making Repairs to the Face of Concrete Walls

    The first thing that you want to do when considering a repair to a concrete wall is to make sure that you are not trying to patch something that will simply fall down in a short period of time. Eventually a all structures will deteriorate Concrete is a pretty permanent product and should last many decades. Water that gets into cracks can cause them to grow and the faces of concrete walls can have the cement binder leached out over many years leaving them weak.

    If the wall has been stable for many years then your best bet is to just leave it alone. If it is painted in our friends case then the the surface should repel water and reduce deterioration but if you want to attempt a fix you can do so by skim coating the surface with mortar.

    There are additives and specific mixes of mortar that are specifically used for this type of repair. Some coatings are also used in a way similar to applying primer to a interior home wall before you paint.

    To begin you want to remove paint and any loose concrete from the surface. Do not get carried away and get aggressive you just want to remove as much as you can so the new mortar will stick to the old.

    Next you want to mix up a batch of mortar and to do so you can purchase premixed in a bag or mix your own by using 1 part cement to 3 parts sand.

    Now you should apply water to the wall where you will be applying the mortar. The wall needs to be moist so that the old concrete won’t leach moisture out of the mortar that you apply and cause the repair to fail. Apply small amounts of water over a short period until it has absorbed water deep into the wall.

    To apply the mortar start at the bottom of the wall and use a un-notched trawl to force it into the wall as hard as you can with some level of reasonablity. You don’t want to knock the wall over or cause damage but you need a firm hand. If the damage is deep then apply a skim coat about a half inch thick and come back and re apply more after you have hit all the other areas that need repair.

    To make the surface smooth you can very lightly moisten the surface with a spray bottle and trawl until smooth. DO NOT USE A GARDEN HOSE do not apply too much water.. you just want a very light mist to allow you to smooth the surface before it cures.

    Once the wall is cured you can follow up with a concrete paint to protect it an match the rest of the wall.


    Final Note

    In the best situation concrete repair is difficult to depend on because concrete does not accept repairs very well. If you moisten the wall surface before applying mortar and make sure it is clean of paint and loose concrete then your results should have a good chance.

    However you must consider that a wall that has been in place for probably 50 years or more and does not show dramatic signs of deterioration and has been pretty stable for at least 5 years back to when it was last painted should not be messed with.

    Sometimes fixing things that are happy and working makes more problems for yourself.. however if you know there is damage that needs repair you can attempt it before taring the whole wall down and doing another pour which is very expensive.



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