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Soil Conditions For Deck Footings

Before you can calculate the size of your footings, you will need to know what kind of soil is present in your yard. Most soils can be classified into three categories: gravel, sand and clay.

Gravel: This type is primarily composed of small stone pebbles that you can see easily with the naked eye. Gravel feels rocky. You cannot roll this soil into a ball. Gravel will drain water very easily and can support the greatest amount of load (3000 lbs/sq ft).

Sand: Sand is composed of tiny particles that are difficult to see with the naked eye. Most sand is tan or white in color. Sand has a rough gritty texture. If you try to roll sand into a ball, it will not hold its shape. If you add water to sand, it will run through very quickly. Sand can support a load of 2000 lbs/sq ft.

Clay: You cannot see clay particles without a strong magnification. Clay feels sticky and can easily be rolled into a ball. It doesn’t drain water very easily. Clay can be many different colors depending on what other minerals it is mixed with. It is the weakest common soil type supporting a load of 1500 lbs/sq ft.

If you are unsure what soil type you will be working with, always use the worst case scenario, which is clay, to make your calculations.

Red Clay Soil
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Red Clay Soil

This is an example of soft red clay soil from Georgia. This type of soil requires a larger surface area concrete footing to distribute the loads of the deck and prevent sinking better than other types of soil.


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Footing Installation

Soil Conditions For Deck Footings

Before you can calculate the size of your footings, you will need to know what kind of soil is present in your yard. Most soils can be classified into three categories: gravel, sand and clay.

Gravel: This type is primarily composed of small stone pebbles that you can see easily with the naked eye. Gravel feels rocky. You cannot roll this soil into a ball. Gravel will drain water very easily and can support the greatest amount of load (3000 lbs/sq ft).

Sand: Sand is composed of tiny particles that are difficult to see with the naked eye. Most sand is tan or white in color. Sand has a rough gritty texture. If you try to roll sand into a ball, it will not hold its shape. If you add water to sand, it will run through very quickly. Sand can support a load of 2000 lbs/sq ft.

Clay: You cannot see clay particles without a strong magnification. Clay feels sticky and can easily be rolled into a ball. It doesn’t drain water very easily. Clay can be many different colors depending on what other minerals it is mixed with. It is the weakest common soil type supporting a load of 1500 lbs/sq ft.

If you are unsure what soil type you will be working with, always use the worst case scenario, which is clay, to make your calculations.

Red Clay Soil
PinterestSave
Red Clay Soil

This is an example of soft red clay soil from Georgia. This type of soil requires a larger surface area concrete footing to distribute the loads of the deck and prevent sinking better than other types of soil.


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Cutting a Concrete Pad

Learn how to use a concrete saw to cut a hole in a patio slab to install a deck footing.

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Footing Size

Learn how large to make your deck footings. Use our table for maximum allowable loads to determine the proper size for your soil type.

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Retaining Walls

Avoid problems related to digging deck footings near retaining walls. Learn some tips from the pros for how to handle these difficult situations.

Next Step: Framing Articles
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How to Decorate Deck Support Columns

Browse some examples of decorative deck support posts for tall decks.

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