Concrete is one of those fickle mysteries that even the most seasoned of DIYers have to take a moment and make sure they are doing everything correctly…too much water and it never sets, too little and you end up with a brittle product.
This is especially true when using concrete to build the posts for your new fence. They have to be sturdy and durable, which is why they need to be installed correctly the first time around.
Living in North Texas surrounded by farms and pastures I drive by fences made from all sorts of materials…concrete fascinates me, so I decided to ask some experts about working with concrete and put it all together here, check it out!
Why Do Concrete Fence Posts Crack?
The most common reason that concrete posts crack is due to either being poured too thin or the ground beneath them not being properly compacted. If there are any weaknesses in the surrounding soil, it will be noticeable when you pour your post because of how quickly and easily they can shift.
If this happens, just take a few steps back and think about what the problem might be. If you are not confident about your handle on concrete, call a pro! It’s much more cost effective to pay someone for their expertise than it is to have them come back out again because of something that could have been fixed right away by an expert who knows how to work with this material.
Concrete that is mixed too thinly will not be able to support itself, which is why it’s important that you get the ratio of water to concrete just right. If your mix seems too dry or crumbly when you are finished mixing in all of your ingredients, add more water.
Concrete can expand and contract depending on temperature changes so if there is not enough room in the form for that expansion to happen, then the concrete will shift and crack.
Adding reinforcement like rebar or wire mesh inside of your post is another way in which you can help strengthen it against any pressure from shifting soil conditions or temperature changes.
How Do You Repair a Cracked Concrete Fence Post?
In general, hairline cracks can be patched with a concrete repair compound. More serious cracks will need to be filled with either a mortar mixture or concrete or you’ll have to replace the post entirely.
If you are planning on patching your post, you should wait until the temperature is between 50 and 90 degrees Fahrenheit! If it’s colder than that outside when you go to do this project, then bring your bucket of dry mix out into the sunlight so that it can warm up before you begin working with it.
For more serious damage that compromises the structural integrity of your post, or if several posts are damaged then you may want to replace the fence with new concrete posts or call in a pro.
If You plan to tackle it yourself and the damage is a little worse than cosmetic, then there are some other steps that need taking care off first:
- Remove any splintered or loose concrete from around the crack
- Fill the gap with sand-mix concrete
- Pour new concrete mix into your form and allow it to dry
Unfortunately, this type of patching is only temporary. Once the concrete has dried there are no guarantees that it will stay put so you have some options if your new post doesn’t seem as sturdy as it should be:
- Reinforce with rebar or wire mesh
- Allow more movement in the fence line by adding a post shim to one side
How Do You Reinforce Concrete Fence Posts?
Typically, the best way to reinforce concrete fence posts is by adding rebar or wire mesh inside of a fresh concrete pour. Wire mesh will help to distribute the weight of your fence and prevent it from bending or breaking while rebar will add a bit more stability.
For this type of reinforcement, you’ll need a mix that is very stiff so that it can support some additional pressure without shifting. Adding too much water to your post mix could compromise its ability to hold up against pressure which is why it’s important to get this part right before you begin.
If your fence is really long, like in the case of a perimeter wall or if there are several posts that need refurbishing then adding reinforcement might be an ideal solution for sturdiness and longevity. This goes double for any post with hairline cracks because even though they don’t seem like very much, they can quickly turn into a problem with no warning.
If you are planning on reinforcing then make sure that to allow enough space for this addition in your form or else it will shift and cause problems while it’s drying. Also, be aware of what kind of pressure is being put on each section so that there isn’t too much strain placed upon one particular area.
Of course, all this is moot if the ground you’re putting your fence posts in isn’t stable. Even if you’ve reinforced your posts, they could still sink further into the ground because of shifting soil conditions.
This is why it’s important to make sure that there isn’t any water pooling around or under where you are placing these concrete fence posts. Water can cause the soil to expand and contract which will keep your posts from staying put.
If you are worried about the damage that has already been done, then adding pressure bars or burying railroad ties around these sections might be another option for reinforcing them against any future problems. This is also a good way of preventing further sinking without having to redo the entire fence.
Can You Straighten A Concrete Fence Post?
If your concrete fence post is strait but leaning, you can level it out and then re-pack the ground around it. You can also use a steel reinforcement wedge to keep the post 90* to the ground. If the posts itself is curved or bowed, you will need to pour a new post and replace it.
Unfortunately, there is no magic trick for straightening a concrete fence post. If the damage to your posts has been severe enough and you’ve already reinforced them as much as possible then it’s time to start thinking about replacement.
Replacing these fencing sections isn’t too difficult especially if they are located towards the middle or end of your property line and you aren’t trying to restore a whole fence line. However, if your posts are located at the beginning or end of a property then it might be more difficult and time consuming to replace them without having to redo all that fencing in between as well
Make sure not to use any non-bonding post treatments such as concrete repair caulk when replacing these posts. This type of caulk will only cause more problems in the long run because it won’t be able to hold up against pressure or shifting soil conditions.
Concrete fence posts are normally very sturdy structures that have a tendency to crack due to an expanding and contracting ground moisture content, extreme weather conditions, weight/pressure applied by leaning or bowing fence posts, and/or using the wrong type of concrete post mix.
How Do You Fix A Wobbly Concrete Fence Post?
Typically, wobbly concrete fence posts can be repaired using anchor plates or by digging the area around the posts out, surrounded the base of the post with pressure treated wood, refilling the dirt and packing it down very well.
If your concrete fence post has become unstable it could be due to pressure being applied in the wrong direction, also known as ‘axial load’. This type of stress happens when there is too much weight on one side of a straightened concrete post.
To fix this problem you can install an anchor plate that will allow for more even distribution across the length of the post. These are available in different shapes and sizes depending on your needs, but they all work to redistribute pressure across a wider surface area which will keep it from pushing itself outwards.
Unfortunately, anchor plates can only do so much if it’s already too late for your concrete fence post. If you’ve noticed leaning or bowing, then it’s already too late to do anything about the damage. In this case, you will have no choice but to replace these sections with a new concrete fence post in order to prevent further problems from happening in the future.
If the post has shifted due to soil expansion or other environmental factors, you can fill in around it with pressure treated wood. Once this is done you will need to remove some of the dirt back out so that there isn’t too much packed into one area.
Final Thoughts
Concrete fence posts can be damaged by an expanding and contracting ground moisture content, extreme weather conditions, weight/pressure applied by leaning or bowing fence posts, and/or using the wrong type of concrete post mix.
If you notice any damage to your concrete fence posts it’s important to act quickly in order to prevent more problems from happening in the future.
The best thing that you can do is replace these sections with a new one because there is really no way to straighten them.
Concrete posts are usually very sturdy structures that have a tendency to crack due to:
- Expanding and contracting of the ground due to moisture content
- Extreme weather conditions
- Weight/pressure (axial load) applied by leaning or bowing fence posts
- Using the wrong type of concrete post mix
If you notice any damage in your fencing it’s best not to attempt to replace these sections with any non-bonding post treatments because it will only cause more problems in the long run. The best thing that you can do is to install anchor plates or by digging the area around the posts out, surrounded the base of your concrete fence post; then refilling and packing dirt down very well.