The frost line is simply the deepest point in the ground to which ground water will freeze. It’s also referred to as the frost depth. When water changes from liquid to solid, it expands 9% in volume.

How far down is the frost line?

The line varies by latitude, it is deeper closer to the poles. Per Federal Highway Administration Publication Number FHWA-HRT-08-057, the maximum frost depth observed in the contiguous United States ranges from 0 to 8 feet (2.4 m). Below that depth, the temperature varies, but is always above 32 °F (0 °C).

Where is the frost line in the ground?

What is the Frost Line? The frost line is the deepest depth at which the moisture present in the soil is expected to freeze. Once the bottom of your footings is buried below the frost line, the residual heat in the ground below the footing will ensure the soil below the footing will not freeze in the winter.

How deep do you have to dig for deck posts?

Dig the holes six inches deeper than the required frost line depth for your area, and slightly wider than the concrete footer tubes you’ll be using.

How deep do posts need to be for a deck?

Set footers a minimum of 6” below the frost line for your area to prevent movement during freezing temperatures. Pour about 6 inches of all-purpose gravel into postholes and pack the gravel tight by using the end of a wooden post.

Does a French drain need to be below the frost line?

A properly installed French drain will begin at the depth of the base of the perimeter beam and is installed with a 1% minimum slope (1 inch in 8 feet). This is usually below the frost line. Generally, those placed below the frost line tend to provide year-round performance, especially in cold regions.

How far below frost line should deck footings be?

By code, the bottom of a footing must be at least 12 inches deep and below the local frostline—whichever is deeper—and bear on stable, undisturbed soil that is free of organic matter. And the code requires a minimum compressive strength of 2,500 psi for the concrete.

What diameter should deck footings be?

The diameter of the footings commonly range between 8 and 24 inches. Most builders use 12-inch diameter footings. The most-common square footing sizes are 16 x 16” as well as 18 x 18” and 20 x 20”. Before calculating the size and number of deck footings, you’ll need to know the type of soil you’re building on.

How deep should Sonotubes be?

Determine how deep you want your tubes. Dig down to the frost line before pouring the concrete. Frost lines vary depending on your region. Start by assuming you want a 10-inch diameter Sonotube that is about 3 feet deep.

What size footings do I need for a 6×6 post?

FOOTINGS: – Poured concrete footings should be a minimum of 8” wider than the posts (4×4 post – 12” min. width, 6×6 post – 14” min. width), a two level deck or deck with roof – 24”x24”. – The bottom of the footings must be a minimum of 36” below finish grade level.

How deep does a water line have to be in the ground?

Exterior piping may be either buried or installed aboveground and shall be well supported and protected against mechanical damage. Underground piping shall be buried not less than 18 inches below the surface of the ground unless otherwise protected.

What is the ground temperature below the frost line?

Ground frost occurs when the ground contains water, and the temperature of the ground goes below 0° C (32° F).

How does frost penetrate the ground?

As the mean air temperature drops in the fall of the year, the surface of the ground will freeze. With the lower air temperatures of approaching winter, the freezing plane slowly penetrates the soil. In a fine-grained moist soil a peculiar phenomenon occurs. At the freezing plane, the water in the soil turns to ice.

Why deck posts should not be set in concrete?

A deck post should always be placed on top of footing, not inside concrete because it can break. The photo on the left shows a post set in a bracket that has been mounted to the top of a footer. The photo on the right shows a post that has concrete poured around it, which can lead to a crack like you see here.

Can I set deck posts without concrete?

Plastic piers require the digging, but unlike footings, there is no concrete involved. The pier is put into the hole and attached the post, giving you your deck without wasting hours installing footings.

How many footings do I need for a 12×16 deck?

A standard deck will need four footings parallel to the house, but they will need to be temporarily braced by 6 inch-by-6 inch posts. Using doubled boards, you will then need to build beams on the top row of the posts to frame the edges of the deck. These must be topped with adjustable post caps.