Concrete footing blocks for decks are basic building elements that snap together to create structures. They resemble children’s toys in appearance. The severely concentrated weights at the bottom of wooden deck posts are meant to be dispersed into firm soil by means of these techniques. They have several advantages and disadvantages and are only one choice for supporting deck weight.
Concrete footing blocks for deck: what are they?
In many aspects, a deck footing block is merely a “precast foundation,” a sort of foundation approved by building codes. Despite not being cast in place, they are nonetheless subject to all of the same criteria as a normal footing with the same concrete mix used. They must be at least 12 inches below grade, or below the local frost depth, and have a suitable bearing area (the portion of the block that rests on the earth). They cannot, however, just be put in a grade level elevation.
Deck blocks should not be mistaken with true concrete piers, which can either be cast in place using precut rebar-reinforced plastic forms and weigh hundreds of pounds each or which can be placed and handled by the typical person. Precast concrete piers must be installed on the project site using a crane or backhoe.
Concrete deck blocks are really simple and resemble the cap on an inexpensive ballpoint pen. The concrete pier block has space inside for a wooden support post for a deck. The block’s concrete lugs function like the sidewalls of a pen cap. You can raise a deck off the blocks just as you pull on the lid to reveal the pen.
It takes a simple and efficient way to deck support.
Concrete deck footing block pros & cons
Concrete deck blocks have more cons than advantages. It’s crucial to understand that the pier blocks are small and provide the least amount of support needed for the majority of decks.
Pros:
Almost always, one person can handle the deck concrete footing blocks.
Concrete isn’t mixed on the job site.
They are affordably priced.
Cons:
There is no mechanical connection between the concrete pier blocks and the wood / concrete deck posts. Hope that the concrete lugs on the block don’t eventually fall off as the post simply rests on them.
The wood/concrete deck post must be partially buried since the blocks must be buried, making it vulnerable to moisture penetration and wood-eating insects. Pictures and accounts of ground-contact treated lumber that has decayed or been attacked by insects are all over the Internet.
Steel reinforcement may or may not be present in the blocks. Concrete’s strength in tension is just one-tenth that of its strength in compression. However, if need be, steel reinforcing should be placed into all concrete used to support decks.
Precast deck blocks as opposed to poured concrete footings
Precast deck blocks are probably best suited for regions where winter frost only reaches a depth of 4 to 5 inches into the soil. The USA has extremely few locations with this type of weather. Remember that the standard deck block has no mechanical means of attachment other than friction with the wood/ concrete deck posts.
Consider employing poured concrete footings or piers that you build on your construction site; you’d probably be better off. Before, accomplishing this required a tedious, multi-step process.
The pier’s hole, which is typically 24 inches in diameter, must first be dug, and only then can a concrete footing be poured. To finish, you would lay on your belly and reach into the hole to smooth and level the concrete.
Additionally, you would need to pause every now and again to properly install brief lengths of horizontal reinforcing steel before finishing with the remaining concrete. Two additional vertical rebar steel pieces should be installed once the footing is even and level in order to create a mechanical connection with the vertical concrete pier that will be installed the following day.
The vertical concrete pier form may be one you built yourself, or you could buy thick, circular cardboard forms and use a handsaw to cut them to the required height. The trick would be to strategically place the tube or form on the concrete footing and then fasten support boards to make sure it wouldn’t move while you filled the hole with concrete.
It is clear from this explanation that this strategy is still used today, but it is not simple.
Fortunately, a plastic deck pier form that produces the footing at the same time as you pour the concrete pier was just developed and launched. The horizontal rebar reinforcing arrives pre-cut and pre-bent, and the form clamps together in less than a minute.
This simple plastic shape only weighs a few pounds when constructed. It is simple for one person to pick up and chuck into a hole. By simply adding gravel to the bottom of the hole, you may modify the height of the pier to exactly where you want it to be. Additionally, lifting the form out of the hole to make modifications is simple.
The form is carefully backfilled with earth to keep it in place while the concrete is being poured after it is just where you want it. There are no annoying support boards to deal with. The shape is secured in place by the surrounding soil.
On average, it takes no longer than 10 minutes to complete snapping the form together and begin pouring concrete.
Purchasing precast concrete deck piers is a third choice. These are very heavy, combined with reinforcing steel, and available in a variety of heights. Only equipment like a backhoe or a crane that can lift the pier and carefully lower it into the footing hole can be used to set them.
To accurately measure the depth of the hole bottoms, you usually require a laser level or a builder’s transit level. A precast pier should only be lowered into a hole once. All of the piers must be plumb, level, and in alignment with one another. Since it is difficult to accomplish, a professional is best suited to carry out this method.
When to use deck concrete footing blocks & how to do it
There are inconsistent regulations across the country about how to attach the deck support post to the concrete footing blocks. Since there is often no physical connection between the post and block, they may not be permitted in some areas with strong winds and worries about uplift pressures.
We don’t want the post to be kicked out when subjected to lateral forces, like when a post is struck by a lawnmower. As a result, lateral restraint at the base of a post is required by building codes. Although concrete lugs that surround the post are frequently protruding on pier blocks, it is questionable if these lugs are strong enough.
In general, low or ground-level decks are most suited for pier blocks because smaller construction materials are more prevalent and extra posts and blocks won’t look out of place there. Ground-level decks also pose less of a risk for post uplift and lateral stresses.
Can concrete footing blocks support a lot of weight?
Given that a concrete footing block typically has a footprint of 12 by 12 inches, it can hold a sizable amount of weight. 144 square inches make up this. An architect or engineer may specify a deck pier footing with a typical diameter of 20 or 24 inches. As a result, the 20-inch footing has 314 square inches of bearing on the soil, whereas the 24-inch footing has 452 square inches.
The majority of homeowners neglect to consider the soil’s ability to support the weight of the deck. The main issue you should be thinking about is that. Your local building inspector should be quite knowledgeable about the soils in all the communities they evaluate, so they can provide you with a wealth of information.
Poor soil is frequently easy to spot. The worst soil is topsoil since it has a lot of organic matter and air. These two qualities imply that topsoil is compressible. When you build on the soil, you don’t want any compression to occur. If the earth smells like a swamp as you dig, that is also a poor indication. There is probably a lot of decaying organic matter in the soil.
A layer of hard clay or potentially a mix of sand and gravel that Mother Nature has compressed over thousands of years is sometimes encountered while digging below the topsoil. Many times, thousands of pounds per square foot can be supported by these soils.
While clay or sandy clay may be able to sustain 2,000 pounds per square foot, some sandy gravels may be able to withstand 5,000 pounds per square foot. Now that you know that a square foot is just 144 square inches, you should be able to see why it makes sense for your deck footing to be 20 or more inches in diameter.
The amount of weight that pier blocks can support is constrained by their limited bearing surface.
How many deck blocks do I need?
You must perform a lot of math to be on the safe side. You must determine the deck’s weight. This can be determined using online weight charts for composite decking, railings, treated lumber joists, and other building materials. When you host a large party, don’t forget to include the tons of weight that will be on the deck.
The next stage is to as accurately you can ascertain your soil’s potential bearing capacity. Estimate the soil’s capacity at only 2,000 pounds per square foot to be conservative.
Imagine for discussion’s sake that your deck would weigh 12,000 pounds when fully occupied by people and furniture. You would require six deck pier blocks as a bare minimum, assuming that the load is distributed equally across all of the support posts. Eight or 10 would be preferable because it’s ideal to be extremely conservative.
Concrete deck blocks should be spaced how far apart?
The distance between the deck blocks may be placed up being 6 or 8 feet. There is no absolute rule. An engineer trained in residential structural design has the knowledge and abilities to choose the spacing. If you’re unsure, spend the money and engage the help of a specialist like this one who can provide you with a precise plan outlining how and where to lay the concrete pier blocks.
What goes under deck footing blocks?
Typically, the soil and concrete footing blocks are in direct contact. It is essential that the soil be solid and compacted as a result. When digging, if there is loose soil at the bottom of the hole, it needs to be removed or compacted with a tamper.
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