How to Prevent Sagging & Sinking Decks

Before you dig your frost footings, you will want to make sure the soil is properly compacted to support the deck load. Often when new houses are built, the process of digging the foundation disrupts the soil and leaves the yard unsettled. This means the entire yard will slowly drop in elevation relative to the house.
It is not uncommon for this to cause patios and driveways to crack. Likewise, if you anchor a deck to footings that are built on soil that is not properly compacted, your deck will probably sink. Needless to say, this is something you want to avoid. If you suspect your soil is unsettled, you will either have to wait for the yard to settle or dig the footings to a depth where the ground is compact. Certain kinds of soils are more problematic than others. Clay soils are particularly prone to shrinking and swelling. If you live in a new house, you may want to talk to your builder or local building inspections department to see if they have any information or suggestions. You can mark the level of the yard as it meets the house where you will be building your deck and observe it over a couple of months to see if you notice any change. If you have reason to believe settling may cause you problems, you may consider hiring a soil engineer to assess the situation, but this will result in an added cost to your project.
Cutting a Concrete Pad
Learn how to use a concrete saw to cut a hole in a patio slab to install a deck footing.
Soil Conditions
Learn how soil conditions can affect the size of your deck footings. Do you have gravel, sand or clay soil?
Deck Footing Depth
Find out how deep you need to dig your footings in your area. Look at our U.S. map of extreme frost penetration.
How to Decorate Deck Support Columns
Browse some examples of decorative deck support posts for tall decks.
How to Connect a Notched Wood Post to a Beam
Learn how to install a notched wood support post to cantilevered beam connection using lag bolts, through bolts with washers or structural screws.
How to Build a Freestanding Deck
You may need to build a freestanding deck if you can't attach a ledger board to the house. Learn how to build a self-supporting deck.
More Helpful Resources
Explore Articles by Topic

Footings
Information related to installing frost footings for decks

Framing
Learn structural framing methods

Decking
Learn about wood and composite decking materials

Stairs
An in-depth look at the complex issue of how to build stairs

Railings
How to install guardrails and handrails to meet IRC code

Features
An overview on water drainage, benches, planters and lights

Design
The basics of deck design

Planning
Learn about permits and working with contractors

Porches & Patios
Build a covered deck to enjoy all seasons

Ledger
Proper attachment techniques

Care
Maintain your deck to maintain your investment

Materials
An overview on water drainage, benches, planters and lights
How to Prevent Sagging & Sinking Decks

Before you dig your frost footings, you will want to make sure the soil is properly compacted to support the deck load. Often when new houses are built, the process of digging the foundation disrupts the soil and leaves the yard unsettled. This means the entire yard will slowly drop in elevation relative to the house.
It is not uncommon for this to cause patios and driveways to crack. Likewise, if you anchor a deck to footings that are built on soil that is not properly compacted, your deck will probably sink. Needless to say, this is something you want to avoid. If you suspect your soil is unsettled, you will either have to wait for the yard to settle or dig the footings to a depth where the ground is compact. Certain kinds of soils are more problematic than others. Clay soils are particularly prone to shrinking and swelling. If you live in a new house, you may want to talk to your builder or local building inspections department to see if they have any information or suggestions. You can mark the level of the yard as it meets the house where you will be building your deck and observe it over a couple of months to see if you notice any change. If you have reason to believe settling may cause you problems, you may consider hiring a soil engineer to assess the situation, but this will result in an added cost to your project.
Cutting a Concrete Pad
Learn how to use a concrete saw to cut a hole in a patio slab to install a deck footing.
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.
Installing footings on a sloped yard
Our inspector explains how to install concrete deck footings on uneven ground.
How to Decorate Deck Support Columns
Browse some examples of decorative deck support posts for tall decks.
How to Build a Freestanding Deck
You may need to build a freestanding deck if you can't attach a ledger board to the house. Learn how to build a self-supporting deck.
Roof Top Deck Construction
Rooftop decks transform otherwise wasted space into beautiful planes for entertaining, dining, relaxing and even gardening. The views will make your deck the talk of the neighborhood and draw frequent guests to your home or business.
Explore Articles by Topic

Footings
Information related to installing frost footings for decks

Framing
Learn structural framing methods

Decking
Learn about wood and composite decking materials

Stairs
An in-depth look at the complex issue of how to build stairs

Railings
How to install guardrails and handrails to meet IRC code

Features
An overview on water drainage, benches, planters and lights

Design
The basics of deck design

Planning
Learn about permits and working with contractors

Porches & Patios
Build a covered deck to enjoy all seasons

Ledger
Proper attachment techniques

Care
Maintain your deck to maintain your investment

Materials
An overview on water drainage, benches, planters and lights