Introduction of Stem Wall
Nowadays, it is very essential that the foundation of the structure should be strong and solid so that it can prevent the settlement of the foundation of the structure.
The Stem walls are considered the backbone of the foundation. The stem walls are part of the slab foundation system, which is often composed of concrete and rebar. If the foundation laid isn’t strong enough to stand the weight, there won’t be any point in erecting fancy buildings. Stem Wall is the same foundation at issue.
In this article, you will learn about of stem walls and the Types of stem walls and their advantages and disadvantages, and concrete stem wall Design.
What Is Stem Wall?
The Stem walls are the common structure that connects the foundation of the building to the walls. The walls are used for the crawl spaces, both vented as well as unvented.
The stem walls are a common type of foundation in the united states. The stem walls are short and attached to the concrete footing. The stem walls are generally used in houses with crawl spaces that are either vented or unvented.
Stem walls are constructed in order to provide support to the walls of any building. As normal, these walls are quite short and are made of cement/concrete and steel.
The construction of Stem Walls may entirely be upon the architects but usually, they are necessary for earthquake-prone areas. Other than this, they are used for houses with crawl space that allows air to circulate right beneath the house/building.
The stem walls are solid and transmit the load from the house to the footing and then distributed to the large area.
Types of Stem Wall
The construction of stem walls is mandatory in certain circumstances. Here we lay down three types of Stem Walls with the intent that it would help you reach the perfect type for your building or house.
1. Masonry Stem Wall
Typically, masonry stem walls are opted for as it’s the best choice for all types of residential houses, regardless of where they are located. However, there is one disadvantage and that is, it needs more supervision and construction resources.
2. Wood Stem Wall
If you are looking for a relatively easier, time-saving, and cost-effective alternative, this one sounds about good.
Wood stem walls work out the best for vented crawl-space construction. However, if one goes for this alternative, they must pay meticulous attention to trivial details coupled with optional vapor retarders.
3. Concrete Stem Wall
Alternatively, one can opt for a concrete stem wall, especially if the region they reside in is storm-prone, as such walls can support any building even through grisly weather. However, this may ask for constant attention, especially when the mixture/cement paste is being made.
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Purposes of Stem Wall
Stem Wall provides support to the walls in perpetuity. Once these mini supporting walls are constructed, you barely need to worry about the building/house that will be relying on them. Other purposes of the same are mentioned below:
- Stem Wall wards off the possibility of structural damage to the house especially when the region is vulnerable to natural calamities. At times, water ends up making its way through the holes and cracks of the wall. In such cases, the stem walls support the structure throughout by not letting the water penetrate the structure.
- Poor construction and execution of stem walls are bound to tamper with the foundation, at times lifting it up which exposes it to the possibility of getting flooded out.
- Stem Walls help to level off the appearance of buildings or houses, thus making it more pleasing to the eyes. Once the base is lifted upwards, the chances of deterioration of the walls by rodents and insects significantly abate.
- The stem wall will help to protect the houses by lifting the base of the house and walls are protected from floods and other aggressive environmental conditions.
- The Stem walls allow easy access to plumbing, wiring, and other mechanical systems compared to the slab foundation.
- It is used to raise the foundation of the building, which helps to increase the beauty of the structure.
- Stem wall will help to keep the structure together and prevent any type of settlement of collapse.
How Are Stem Walls Foundation Constructed?
The construction of such supporting stem wall foundation may vary, however, the following are the few common steps that need to be undertaken when building them:
- To begin with, weed out any wild plants, grits, and other unwanted debris on the site. All the unwanted plants which are present on the site are removed and the site is cleaned properly.
- The next step of the stem wall foundation is to nestle the subgrade. For this, get a plate compactor and add pertinent materials to the soil with the purpose to achieve the perfect soil. However, if you are working on bigger projects, you will be needing bigger equipment.
- Once the above step is executed pouring footings. Bear in mind, the concrete bases for the stem walls must go 12 inches beneath the undisturbed soil and frost line, failing to do this will lead to pushing up of footings. The size remains the same width-wise as well.
- Stem walls are alternatively known as “two-pour foundations” as the first pour goes for the footing and the second for the stem walls.
- While the construction of the stem walls above the footing is being carried through, one must shovel in vertical bars to make sure the base is steadfast.
- After reckoning with and performing the above-mentioned steps, secure a sill plate to the stem walls using anchor bolts and you are good to go.
Advantages of Stem Wall Construction
There are multiple advantages of the Stem Wall as discussed hurriedly in the previous sections. There are some pronounced advantages as well and those are:
- The primary advantage of Stem Walls is that they are solid and can carry the weight of a house by distributing the weight to a much wider area.
- Stem Walls construction prevents mishap or dismantling of the house in catastrophic situations by raising the base higher.
- Over and above, plumbing, wiring, and other important work can easily be carried through.
- And finally, the more the house is lifted, the better it looks to the outsider’s eyes.
Disadvantages of Stem Wall Construction
There are a few disadvantages of this much-celebrated support system and those are laid out below:
- The predominant disadvantage of such a construction is that it takes time and once the work gets approval, it has to be brought to a satisfactory end. You cannot leave it halfway through.
- Another major downside of such a support system is that human resource is a necessity and you will be needing a lot of it.
- Lastly, if you are planning on getting one of these built, be ready for a backfilling.
Stem Wall Foundation Cost
The cost of the Stem Wall foundation can vary from region to region. The only thing that is fixed and is likely to charge you a good amount is the concrete, anchor, and other materials you will be needing in this process.
If we tote up the stem wall foundation cost of human resources and machinery(if working on a bigger project), the overall cost significantly shoots up.
Compared with other houses, stem walls require lots of effort, and money, depending on which foundation you required for your structure. The cost of the stem wall generally ranges between $7,000$ to $21,000.
Stem Wall Vs Crawl Space
Stem Wall and Crawl Space slightly differ from one another. A crawl space foundation supports the house by ground level by 2 meters approx. whereas stem walls, on the other hand, provide long-term support to the house/building by distributing the weight of it to a relatively wider area. This is the prime difference between the two.
The similarity, however, lies at the heart of its nature to hold the house upright.
Stem Wall Vs Retaining Wall
Stem Wall is one of the main components that make up a retaining wall, the other components are the toe, the Heel, and the Shear Key. Over here, the stem wall is backing the backfill whilst the other three are the portions of the footing at the front side backfill side and under it as well.
As mentioned above, a stem wall is no different than a retaining wall, and if anything at all, it is a part of it.
Monolithic Slabs Vs Stem Walls
The aforementioned foundations are the most popular on the market right now. Let’s decide whether the former is one upon the other or the latter.
1. Flat Land Requirement:
Over here, monolithic slabs take the cake as all they need is a single pour and are also laid faster than the latter, for the latter requires intensive labour.
2. Calamity Proof:
As for this, Stem walls can be blindly pitched on as they provide support to the house by elevating it a tad bit.
3. Sound Structure:
Flood-hit zones having houses built over stem walls are less at risk of getting engulfed by the waves.
Concrete Stem wall design
The Design of the concrete stem wall is as follows:-
The design of the stem wall foundation details is the same as the retaining walls. It has a strip footing or a pad footing at the bottom with loading applied on the top of the fill material.
Design Code For Concrete Stem wall:
Most of the designs of the stem walls follow IRC 2003 Code.
1. Concrete Stem Wall Height:
According to the, 2003 IRC Code, the maximum height of the stem wall should not be more than 4 feet. For the stem walls having a height of more than 4 feet, there should be additional reinforcement should be provided.
2. Width/Thickness of Concrete Stem Wall:
The minimum width of concrete stem walls is 6” for single-story buildings.
3. Footing Pad for Concrete Stem Wall:
The bottom footing pad in the concrete stem wall is 12” minimum while for two stories it is 15” minimum.
4. Depth of Concrete Stem Wall:
The thickness of the concrete footing pad is between 6 inches to 7 inches. The minimum depth of the stem wall footing pad from the grade to the bottom of the footing is 24”.
5. Pouring Sequence for Concrete Stem Wall:
The Mostly two types of pour system is used for pouring the slab. The concrete footing pad is poured with projecting steel bars while the upper wall is built afterward with a construction joint in between.
6. Reinforcement of Concrete Stem Wall:
A “J” shape rebar is provided having a vertical shape with 4 number of diameters with over the center spacing of 48” having 90” hook at the end of the bar to make it monolithic with the footing pad.
There are also two horizontal rebars are provided one at the footing hook while one from 12” at the top.