Can You Pour Concrete Over Grass?

 Why you shouldn’t pour concrete over grass

The first thing you need to do when preparing to pour concrete is to make sure that you have a flat area of compact earth that is free of stones and debris.

 

Grass regrowth can lead to cracks

If you are going to pour concrete onto an area where there has been grass, then you need to prepare the area first so that it is ready for the concrete.  To do this, you need to remove all of the grass and its roots by digging a few inches into the soil.

 

This should prevent the grass from regrowing and it is essential as grass and weeds can easily grow up through any small cracks in the concrete and push their way up, making a small crack much bigger and more noticeable.

 

You will have an uneven base

You must create a strong and sturdy base to pour the concrete onto or you will just end up with a number of problems after it has set.  As the concrete begins to dry, it settles down onto the earth.  If the base underneath is not even before you begin then the concrete will not set even and you will end up with cracks in the concrete or slanted slabs.

 

Gravel or sand base

Concrete must have a base of either gravel or sand before you pour it on top.  This is important because sand and gravel does not get affected by the weather and does not exhibit any changes as the weather changes.  As it does not expand or contract then it should not cause the concrete on top of it to crack.  Also, if you do not use a gravel or sand base, but pour the concrete onto a grass base, then the earth and grass underneath the concrete are more likely to move, which can cause problems for your concrete.

 

However, if there is gravel and sand already in your soil then you don’t need to use more to create a base.  In that case, you can just remove all of the grass and so long as your earth base is even then the concrete can be poured straight onto it.

 

Can you ever pour concrete over grass?

There is always the risk of cracking if you do pour concrete straight onto grass as the grass will always try to find a way back up to the surface through your concrete.  However, sometimes you might have no other option but to do it - if you don’t want to remove the grass, or you are unable to remove it for some reason - and if that’s the case then there are occasionally times when you can pour the concrete straight on.

 

l Make the concrete more than six inches deep - there are never any guarantees that it will entirely prevent the grass from growing through the concrete and forming cracks, but generally the deeper the concrete, the harder it is for the grass to grow and the longer it will take it to reach the surface.

 

l It’s temporary - if you don’t plan on leaving the concrete down for more than a couple of years then the grass won’t be a problem.  In this case, you can pour the concrete on and it will set and do the job you need it to until you’re ready to remove it.

 

l You don’t mind the work - if you’re quite happy to put in the time and effort needed to maintain the concrete by repairing the cracks as soon as you find them then there’s no reason why you can’t pour the concrete straight onto the grass.

 

l You don’t mind cracks - if you’re only using the concrete for small projects such as  an outdoor utility area or around a mailbox then a few cracks probably aren’t going to be an issue for you.

 

How to pour concrete onto grass

If you have to pour your concrete straight onto your grass then you can prevent problems later on by doing a few things.

 

Planning ahead is a good place to start - knowing exactly where you want to put your concrete before you begin to put it down can prevent you from ending up being unhappy with it once it’s too late to do anything about it!

 

Best concrete to use on grass

It is essential that you have the correct mix of concrete for the job you want it to do.  You also need to make sure that you buy one that is designed for outdoor use - one that is fast-drying and requires little preparation is ideal.  Consider the following when choosing your concrete:

 

1. Quick-drying: Ideally the concrete should be a mix that will take 24 hours or less to dry as this reduces the risk of footprints or other marks being made in it, and also means that you’re not having to worry too much about unpredictable weather.

 

2. Easy to use: A mix that doesn’t take a lot of preparing makes life a lot easier, and concrete that only needs mixing with water to prepare it should reduce the risk of any errors being made.

 

3. High quality: There’s no point in buying something that is low-quality and ending up with it not being right for the purpose it’s intended for.  Therefore, your concrete should be a combination of sand, water, stones and concrete “paste”.  A mix that contains approximately 15% concrete and a high percentage of rocks is the best to use.

 

Till the grass

Tilling the grass where you’re going to pour your concrete can really make a difference as it shreds the roots and should prevent the grass from growing back.

 

Pour the concrete

1.  Mix the concrete with water at the recommended amount and ensure that it is mixed thoroughly as it’s really important that you make it correctly.

 

2. Use some wooden boards to mark the area where you are going to pour the concrete.  This will give you straight edges and prevent concrete from going anywhere it’s not supposed to.

3. Pour the mixed concrete into the area that you have marked out so that it completely covers the area.  Make sure that it doesn’t overflow the boards or push them out of place.

 

4. Make sure that you pour the concrete so that it is at least a few inches deep to help prevent it from cracking once it has any weight or pressure put on it.

 

5. Allow the concrete to dry before removing the wooden boards.

 

Tip

If the concrete is uneven around the edges then some decorative stones or something similar can make it pleasing to look at and hide any faults in the concrete.