Building Site & Size Recommendations

Deck Heights

What is the Maximum height for a Floating Foundation Deck System?

The maximum height for the floating foundation deck system is 60 inches (5 feet). Any deck from ground to the top decking that is higher than 30 inches requires 2x4 diagonal bracing around the perimeter of the deck.

What is the Minimum height for a Floating Foundation Deck System?

Built to DekBrands specifications using 2x6 treated lumber for supports and decking, a Floating Foundation Deck System's minimum overall height is 13 inches. This is the height of the Dek-Block® pier to the support board (6") plus the height of the support board (5 1/2") plus the decking surface board (1 1/2"). Can I bury the Dek-Block® piers?

Can I use a 2x4 support boards (instead of 2x6) to lower the height of the deck?

I only have 6 - 8 inches from my back door to the ground. What can I do?

Sorry, but there is really no way using the Floating Foundation Deck System to get the deck to a 6 inch height. The lumber alone is 7 inches. Burying the Dek-Block® piers slightly may help in some situations.

Sometimes, there isn't a great solution for shallow heights. The best solution we have seen is as follows:

Dig a 4-6 inch hole that is approximately the width of the doorway and depth of 3-4 ft. Backfill 2-4 inches of the hole with crush rock, stone or sand. Place 2 inch concrete patio stones on the fill. On top of the patio stones place a support frame out of 2x4 or 2x6 lumber. It's always a good idea to use a stand off bracket to elevate the lumber from the patio stone slightly. Use decking boards to match the larger deck. After completing the small box step platform, build the "main" deck at the minimum 13 inch height around the platform.

Take a look at what others have done with this same dilemma.

Frost Heave

What does frost heaving and thawing mean?

Frost heave is caused by water that is trapped underground in layers of soil that have become frozen. When the water freezes, the mass of the soil expands, causing the surface to move vertically. If this process were to occur in an open field with undisturbed soil, the ground would rise during the winter and settling back down again in the spring as the trapped water thaws.

How much movement is created from frost heave?

Every region is different. The colder the climate the more the movement will occur. We are located in Minnesota. During the winter months, about 1/2 inch of rise will occur during extreme conditions.

Even if you live in a warmer climate like Texas, the principles are the same. The soil will expand and contract with temperature change. It will be dramatically less than a climate with frost, but movement does occur.

How does frost heave affect conventional deck construction?

When footings are not buried below the frost line or without smooth edges, damage can occur. During cold seasons, ice lenses form, exerting pressure against the rough edges of the concrete post, forcing it upward. A pocket will form under the post where the soil is not affected by frost. Dirt particles and water will then accumulate into this pocket. During the spring thaw, it is likely that the post will not return to its original position (due to the accumulation of soil deposits). When repeated throughout the life of the deck, this process of lifting the post can cause significant damage to the structural integrity of the deck.

How is frost heave prevented?

How does frost heave affect the Floating Foundation Deck Systems?

The Dek-Block brand pier sits on top of the ground, moving up and down just as your driveway or sidewalk would. The structure is part of a system and is designed to accommodate the frost movement. Not fight against it.

When building next to a door, place the deck height about 1/2 inch below the door's threshold.

Attaching the Deck

Can I attach the Floating Deck to my house?

No. Attaching the deck to your house is not recommended. Your floating deck will be raising and lowering uniformly during seasonal changes. This will exert tremendous force on both your deck and your house exterior, eventually causing damage to both. Even in the south were frost does not occur, there is still movement. Attaching a floating deck does not conform with any building code.

Can I attach the Floating Deck to an existing deck or porch?

No. Just like attaching the Floating Deck to a house, attaching a Floating Deck to an existing deck or porch that is built with conventional construction methods will have the same effect. Eventually both will be damaged due to seasonal frost heave. For more information on frost heave Click Here.

Will my deck move sideways or pull from the house?

No. When frost heave occurs, the forces in the ground have nowhere to go except up. The deck will move slightly up and down, but not from side to side. It will not pull away from the house.

Ground Preparation

Do I need to put anything under the Dek-Block® piers?

It's not really necessary to put anything under the Dek-Block® piers. They can sit directly on top of the soil or grass. Use a tamper or drop the Dek-Block® pier a couple of times to compact the top few inches of the top soil. Following DekBrands spacing requirements, the weight is spread evenly over multiple Dek-Block® piers and not concentrated onto only a few locations.

Can I put anything under the Dek-Block® piers if I want to?

Yes. But, if you do put anything under the Dek-Block® piers it should be compacted or tamped before placing any piers. Crushed rock, sand or gravel are great bases.

Can I build on new construction or recently backfilled ground?

If the ground where you plan to build your deck was recently backfilled, you need to let the ground settle before building. Typically 70% of settling occurs over the first year. We recommend you wait a minimum of 2 years before building a Floating Foundation Deck on recently backfilled ground near the foundation of your house.

Will my deck sink?

Even on poor soil conditions, your deck will not sink. DekBrands Floating Foundation Deck Systems are designed as a "weight distribution system", spreading the weight EVENLY across the ground. It is essential that you follow the layout provided in the plans or the recommended spacing of Dek-Block® piers.

There is a simple non-technical method to determine if your soil is suitable for a DekBrands Floating Foundation Deck System: the shoe print test. Under normal situations, if a person's shoe sinks into the ground more than 1/2 inch while they are walking, the soil may not be suitable for construction and corrections need to be made.

What do I do if the ground is sloped?

If you need to have Dek-Block® piers placed on sloping ground - you should cut into the soil so that the Dek-Block® pier will be resting flat and level. Only remove the soil under/around the pier. You do not need to level the entire site.

Can I bury the Dek-Block® piers?

It is not recommended to bury the Dek-Block® pier more than 2 inches for climates that have seasonal frost. Areas that are without frost (such as Arizona, Florida, Southern California and Texas) can bury the Dek-Block® pier if needed up to 4 inches. Be sure to leave at least 2 inches of the Dek-Block® pier exposed between the ground and where the support board will sitting. This will allow for air flow in preventing rot and insect attraction.

If the Dek-Block® pier were to be buried in climates where frost occurs, the Dek-Block® pier will slowly creep up and out of the ground over time. Take a look at what occurs with frost heave.

Anytime the Dek-Block® pier is buried, verify there is proper drainage away from the pier and hole. Otherwise, you will have a small holes to collect water under your deck.

What about using a weed barrier or fabric?

Typically nothing will grow where the sun does not shine. If you'd like to, you may want to place a weed barrier along the outside edges of the deck once the framing is complete. Placing a landscaping fabric before start can be a mess. It is real easy to rip or trip on the fabric while building the deck.

Over a Patio

Can I build over a patio or stoop?

Yes. As long as the patio or stoop is not frost protected (using footings buried down to the frost line - very uncommon for patio's). A patio or concrete slab is very similar to a Floating Foundation Deck System, it rises and falls uniformly during seasonal ground heave.

My concrete patio or stoop has less than 13" between the ground and the door.

The floating foundation deck system sits at a height of 13" when properly assembled with 2x6 support boards and decking. Your building site needs to have this clearance plus a 1/2 inch for a space between the deck and the doors threshold. If you need a deck that is lower than 13 1/2" due to the placement of doors or other structures on your home consider building with these methods.

1) You can build directly on top of patios using blocks of wood or stand off brackets between your support frame and the concrete. We do not recommend this method for areas larger than 20 sq. ft. Click here for a good example of building over a concrete stoop.

2) If the area to be lower than 13" is greater than 20 sq. ft. you can build your deck with a landing around your door. This will allow you to step out of your house at the current ground level, and then step up onto the deck that can be built at the proper height of 13". The image below shows one home owners solution, your landing can be any size needed.

Can I build my Floating Foundation Deck half on a patio and half on the grass?

Yes. As long as the patio meets the criteria above (not frost protected), there is no problem building the deck half on and half off of the patio.

Building on a Roof

Can I use this Floating Foundation Deck System to build a deck on my roof?

No. A roof is typically designed only for the weight of the materials on it, snow loads and the weight of people for repair, etc. Adding a deck and a greater number of planned people can be a significant change in structural loads than what a roof is built to accommodate safely. This type of application absolutely needs to be reviewed by an engineer BEFORE PROCEEDING.