Unit 2 Concrete Basements

1. Introduction

1.1 Read the text title and hypothesize what the text is about. Write down your hypothesis.

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1.2 What do you know concerning this issue? List your ideas in the table left column “I know”.

I know	I have learnt

3. If you know answers to these questions write them down in the space given after each question.

1	What is concrete?
2	What is it necessary to do to install a basement?
3	Where is a drain tile located?
4	What materials are used for building basement walls?
5	Where is the floor poured?
6	What does a footing drain consist of?
7	What are the advantages of concrete?

4. Circle in the list the words and expressions you know. Write down their translation in the table and calculate the percentage of your lexical competence.

1	dimensions		9	leakage problems
2	substantially		10	solvents
3	to install		11	to insulate
4	reinforcing steel		12	virgin soil
5	strength		13	drain tile
6	recreational space		14	precast panels
7	to backfill		15	to bond
8	exterior walls		16	masonry walls

Basements are a valuable part of any new home, with benefits far outweighing cost. Concrete is the material of choice for basement construction. A properly constructed concrete basement will provide adequate support for the home above it and can be used to economically expand the family living area. A good concrete foundation does not crack or leak water.

Concrete. Concrete is a mixture of Portland cement, sand and gravel (often called aggregate). Portland cement is the glue that causes the mixture to harden or consolidate into a durable construction material. This hardening is caused by a chemical reaction between the cement and the water used in mixing the concrete.

Reinforcing. Concrete has excellent strength for bearing but very little strength in tension or bending. This means that walls will frequently crack due to pressures exerted by the soil around them. To prevent this, reinforcing steel is placed in the concrete to provide added strength. The exact amount, size and placement of reinforcing steel depend on the particular characteristics of the soil in your area.

C omponents of a well-constructed basement.

Reinforcing steel represents a relatively small portion of the total basement cost. However, a lack of reinforcing steel can lead to reduced performance and major leakage problems throughout the life of the home.

Foundation drainage. No matter how well the basement is constructed, it will leak if the groundwater table outside is too high. A drain tile located at the base of the wall prevents the water level outside of the home from building up, causing pressure on the wall and then leakage. In areas that are normally wet, a second drain tile is sometimes placed under the basement floor on the inside wall.

Components of a well-constructed basement

Wall coating. A liquid asphalt compound is usually applied to exterior walls below the ground level to seal up small openings in the concrete surface. The best results are achieved with sprayed-on hot compounds. However, brushed on cold materials can do a satisfactory job.

Rubber sheet materials and special clay sealing compounds are available for exterior treatment of basement walls when extreme moisture conditions exist.

Insulation. It is economical to insulate basement walls. To do this at construction time, apply a layer of expanded polystyrene foam insulation to the exterior. In some cases, polystyrene can be placed directly in the concrete forms before pouring the concrete. This is an excellent practice because concrete bonds very well with polystyrene.

Caution. Do not use asphalt compounds on walls covered with polystyrene. The solvents in the asphalt often dissolve the polystyrene foam.

Backfill. Replace the soil around the outside of the basement in 12-inch-thick layers. Be careful not to push large rocks against the concrete or insulation. The final layer of backfill should be graded or sloped away from the foundation so that surface water is carried away rapidly.

Many builders prefer to do backfilling after the house subflooring is in place. This provides extra strength in case too much earth is pushed against the wall too rapidly.

Basements provide inexpensive space for many uses. A basement’s sturdiness and location make it ideal for housing mechanical equipment like furnaces, water heaters and other utilities. These same properties make it an excellent choice for recreational space, storage areas, workshops or hobby rooms.

Basements typically house main electrical lines, plumbing and ductwork, making these easily accessible for changes and repair. The sheltering properties of below-grade space make basements “safe havens” for occupants during hurricanes, tornadoes and severe thunderstorms. With a few upgrades, basements can be transformed into entertainment centers, offices or extra bedrooms for a growing family. This provides a homeowner future expansion potential without the cost of constructing more floor space above ground, and can also substantially increase the resale value of a property.

To install a basement or crawlspace into a home, it's necessary to dig a hole bigger than the foundation and its walls to seat the structure inside. These steps are as follows:

• The foundation hold is dug out of the virgin soil, creating an enormous hole.

• The footing is installed inside. This footing is the base of your foundation and is very important. It keeps your house from sinking into the ground and must be strong enough to withstand the continuous forces of nature.

• The walls are built of poured concrete, block, stone and (rarely) out of treated wood.

• Some of the dirt removed by the excavation is backfilled in over the footing.

• The floor is poured between the walls on top of the backfill.

• Usually, a footing drain is installed at this point. Most often, this drain consists of a perforated pipe that lies in a bed of 3/4" of stone. As these stones lay on top of one another, they make 1/2" spaces in between. The purpose of these stones is to filter the dirt out from the water.

W hy is my basement built of concrete? For basement construction, concrete is by far the product of choice. Concrete provides a permanent, stable base for a house to rest on and creates an enclosed space protected from the ground, rodents and weather. Sturdy concrete walls are highly resistant to shifting or sagging under ground and water pressure, often for a century or more. When necessary, strength can be enhanced by increasing wall thickness and embedding steel reinforcing bars inside the concrete. Concrete does not rot, warp, rust, deteriorate or provide a food source for mold in the presence of water or moisture. Concrete doesn’t burn and can’t be eaten or damaged by termites, insects or vermin. Properly designed concrete walls keep out water, radon and outside noise. They can also be constructed with a durable architectural finish and high insulation value.

W hat are the different ways of building basements out of concrete? Cast-in-place concrete using removable forms (sometimes called “poured concrete”) produces an economical wall with a hard, durable surface on both sides. Concrete masonry (block) walls can also provide an architectural surface in many different colors and textures, for a distinctive exterior appearance and an attractive interior finished wall.

Insulating options are available for both cast-in-place and masonry wall systems, depending on desired results. Insulating concrete forms (ICFs) create a highly energy-efficient wall that is ready to finish with traditional gypsum wallboard on the interior surface.

S olid precast panels are also pre-insulated, ready for wallboard, and go up rapidly in almost any weather. Some precast panels have insulation “sandwiched” into the center of the wall, providing a smooth finish that doesn’t require wallboard. Autoclaved aerated concrete (AAC) blocks are made of a lightweight concrete with good insulating properties.

CONSTRUCTION OF REINFORCED CONCRETE BASEMENT.

The excavation allows sufficient room to position the formwork for the reinforced concrete walls. Blinding concrete has been poured over the ground and a waterproof membrane has been placed. Reinforcement has been fixed for the floor slab and vertical starter bars can be seen.

• Note that the reinforcement is ribbed to enhance the bond between the bars and the concrete. All high tensile steel bars are ribbed in this way.

• Note how the reinforcement is kept above the insulation to ensure sufficient cover when the concrete is placed. The concrete is to be placed by a pump and its discharge pipe is being connected together.

• Note how the bars are wired together to create stability within the reinforcement cage. This is essential to prevent the reinforcement from becoming displaced when the concrete is poured.

What should I look for to be sure I'm getting a quality basement?

• It is important to hire a reputable, experienced contractor.

• In many areas it is necessary to install components that keep ground water away from the perimeter of a home.

• If you are planning to use the basement for storage, work or living space, inspect the plans to make sure ceiling heights are adequate and mechanical equipment is located out of the way.

• When construction is complete, check that all basement dimensions match those on the plans. Walls should be straight and precisely vertical.