Four Tips To Consider If You Want Concrete Under Your New Deck

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If you're putting in a new deck, you may want to add concrete underneath it. Depending on the height of your deck, the concrete slab can serve as a ground floor patio under the deck, or it can provide a stable spot to store items without worrying about mud or dirt. If you are building a deck over an existing slab of concrete, you can even anchor the deck directly to the concrete. 

Before you get started, you should consider the following tips. These tips can help guide your designs in the right direction, and they can help you figure out which questions you should be asking your deck installer.  

1. Pour the slab first.

Ideally, you should put in the concrete slab before you put in the deck. This approach gives you the ability to move freely around the area. In contrast, if the deck is put in first, you may not be able to get the concrete mixer under the deck, and you may be stuck doing the whole job while hunched over.

In cases like that, you may want to skip concrete and opt for patio stones or gravel instead. That provides the same effect as concrete, but these options are easier to deal with in relatively cramped quarters.

2. Consider making the slab smaller than the deck.

If you're able to put in the concrete slab first, make sure that you get accurate deck measurements from the deck installer before you start working on the concrete. Ideally, your concrete slab should be slightly smaller than the surface area of the deck.

By using a slab that is smaller than the deck, you allow the deck's supporting posts to be sunk outside of the slab. This is important because if the wood ages and needs to be replaced, you don't want to end up breaking the slab to remove the posts.

3. Surround posts with styrofoam.

If you want your concrete slab to be the same size as your deck or even larger, that can be possible. However, in this case, you need to have your deck installer on site when the concrete is poured. Ideally, you should put something around the deck's supporting posts so that they don't bind to the concrete. For example, a thick layer of rubber or styrofoam can work.

Once the concrete has set, you can remove the styrofoam or rubber. However, don't just leave the area around the deck posts empty. Instead, pour gravel or sand in there. That keeps the deck posts stable while still allowing for concrete expansion due to frost or freezes. Additionally, if you have to replace the deck posts in the future, you can remove them without worrying about breaking the slab.

4. Get creative with existing concrete slabs.

If you already have a concrete slab in the area where you want to put your deck, there are a few different options, and you may want to talk with your deck installer about which one is best for your situation. In some cases, you can put a deck directly over the slab — this even works for slabs that are old and cracked. In other cases, you may want to explore a setup similar to those discussed above where the posts are just on the outside corners of the deck, and the deck is raised.

If you want the deck to be the same size as your existing concrete pad, you may be able to hire a concrete cutter to remove some of the concrete. Then, your deck installer can put the posts into the new holes. However, this is a delicate job that typically requires the help of a professional. 

For more ideas on putting concrete beneath a deck, contact a deck installer from a company like Rainier Fencing & Decking. They can help you narrow in on the best options.

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1 February 2017