Generally speaking, there are three main types of basement construction, namely poured concrete, precast panel, and masonry walls. The three are similar and sometimes interchangeable, but a lot depends on the type of structure at issue. Local area and soil composition can also factor into the decision. Areas with a lot of rainfall or notoriously rocky, aerated soil may not be as suitable for certain methods as would drier, sandier ground. Sometimes local codes and building regulations specify which type must be used, but in many instances this is a decision left up to the contractor or construction manager individually. Research into the different options is often the best way for people in these positions to make the best choice.
Basement Basics
Basements are foundational fixtures that help give homes and other buildings added strength while also usually capitalizing on available storage space. It is almost always the case that basements must be built before the structure sitting atop it, or at least at the same time. Most are basically rooms sunk into the ground at the foundation level, and as such they can be difficult to install once that foundation is already in place and being used.
Regardless of their specific construction type, almost all basements perform a specific structural job for the building as a whole. Their walls act as additional and supplementary foundational materials, and their ceilings serve as the ground floor for the structure. As such, they must be constructed to be durable and to withstand the weight of the structure as a whole, or at least to help distribute that weight in an even way. In most cases the flooring sits directly atop the soil, though in locations where soil drainage is a serious concern the basement may contain a drainage system, often slanted or using stilts, that can shuttle water away from the foundation and into some sort of a runoff system.
Poured Concrete
A poured concrete basement tends to be the choice used most often. The basement contractor may begin by pouring the footing for the basement foundation. After this is set, forms can be used to hold the poured concrete walls in place as they dry. The inside of the forms may need to be oiled before the concrete is poured to prevent the form from sticking. Poured concrete walls tend to be stronger and often require fewer repairs as the home ages.
Precast Panels
The precast basement panel can be created in much the same way as poured concrete is. In this method, basement walls are generally molded at a location other than the building site — a construction studio, for instance, or an off-site concrete works. The walls can then be transported to the building location and placed on the footer. While the integrity of the walls may be similar to the poured concrete wall, a crane is almost always needed to place the walls on the footer, owing to their weight and size if nothing else. The cost for such major equipment even if just rented can increase the total cost of the basement construction, though the improved craftsmanship of the walls and the added time to check for defects before installation can improve overall quality.
Masonry Walls
Creating a basement using the masonry wall method can be one of the least expensive options These walls are often made from concrete masonry units (CMUs), also referred to as cinder blocks. The large size and hollow interior of the cinder block can reduce building time. To increase durability, the basement contractor may reinforce this material with steel rebar and concrete. The hollow insides of the cinder block allow the contractor to pour concrete into the center, which is more efficient — both in terms of time and money — than pouring slabs from scratch.
Foundational Considerations
After construction is complete, some contractors bury the basement underground. To achieve this, the basement system may be started inside a hole excavated before the foundation was built. Once the basement construction is complete, the soil can be replaced around the foundation walls, and construction can continue on the rest of the building. The basement contractor may choose to waterproof or protect the foundation in some way before burying it, though a lot of this depends on location and soil conditions.