Self-Help Construction of 1-Story Building (Peace Corps, 1977, 235 p.)
 Appendices
 Calculations to check whether a proposed site will support a building Step-by-step directions for drawing foundation plans Estimating the amount of concrete needed for a floor Estimating materials needed to build walls Reference tables for concrete construction Metric measurements used in this manual and their U.S. equivalents Sources of further information ''Human measuring pieces'' for designing room size and floor plan

### Calculations to check whether a proposed site will support a building

If there is doubt whether the soil at a proposed site will support a building (see page 18) it may be necessary to estimate both the weight of the planned building and the weight-bearing capacity of the soil. This section contains step-by-step directions and tables for both these estimates.

IMPORTANT NOTE: The weight of a planned building cannot be estimated until the builders have decided:

· its size and shape;
· what its walls will be made of and how thick they will be;
· what kind of roof it will have.

CALCULATING A BUILDING'S WEIGHT PER SQUARE METER

Several calculations must be made to estimate a building's weight per square meter. For the purposes of estimation, figure that:

Equation 1.
Weight per square meter = [ weight of longest wall (kg) + weight of roof supported by longest wall (kg) ] / length of longest wall (m)

To find the weight per square meter, therefore, the planner first needs to determine each of the three items on the right side of Equation 1. Follow these steps:

STEP 1. Enter the planned length of the longest wall in Equation 1:

Equation 1.

STEP 2. Calculate the weight of the longest wall.

Equation 1.

(a) Use the following equation to determine the weight of the longest wall:

Equation 2

(b) Use Table A to find the weight per sq. meter for every centimeter of wall thickness of the material with which the building's walls will be built.

 Table A wall material kg/sq. meter per centimeter wall thickness concrete block 90 stabilized earth 125 sand-cement block 75 adobe 125 stone/rock 150

(c) Multiply the number you find in Table A by the thickness of the building's walls. The result will
be the weight of 1 sq. meter of wall; enter it in the correct place in Equation 2:

Equation 2

(d) Next, multiply the length of the longest wall in meters by its height. The answer will be the number of sq. meters in the wall. Enter this figure in the correct place in Equation

Equation 2

(e) Compute the weight of the longest wall based on the figures you have entered in Equation 2 in steps 2(c) and 2(d).

STEP 3. Estimate the weight of the roof supported by the longest wall.

Equation 1

(a) Use the following equation to estimate the weight of the roof supported by the longest wall:

Equation3

(b) Use Table 8 to find the estimated weight of the roof per sq. meter. If you are in doubt about the roof-style planned, use the figure on the table for flat roofs. Enter the figure you find in Table B in Equation 3:

 Table B Roof style Roof load per sq. m pitched 170 kg flat 190 kg

Equation 3

Weight of roof supported by longest wall = weight of roof per sq. meter × number of sq. meters in roof

(c) Next, multiply the length of the roof by its width. If the roof has not been planned yet, assume that it will be 1 meter longer and 1 meter wider than the building. The answer will be the number of square meters in the roof. Enter this figure in the correct place in Equation 3:

Equation 3

(d) Compute the weight of roof supported by the longest wall using the figures you have entered in Equation 3 in steps 3(b) and 3(c).

STEP 4. Enter the figures you calculated in steps 1, ate), and 3(c) in Equation 1, and calculate the weight of the building per square meter:

Equation 1

STEP 5. Finally, compare the building's weight per square meter with the weight - bearing capacity of the soil at the site indicated in Table C.

 Table C Type of soil Weight-bearing capacity (kg/sq.m) Soft, black, drained marsh, or "fill" 4,900 - 10,000 Gravel, sand 29,400 Hard - packed clay 58,800 Rock 156,000

Weight per square meter

SAMPLE CALCULATION OF A BUILDING'S WEIGHT PER SQUARE METER

Here is a step-by-step sample of how the weight of a building would be estimated, following the procedure outlined on pages 202-205.

Assume that the building pictured above is planned to be 7.5 meters long and 2.4 meters high along its longest wall; assume also that the walls will be made of 20cm thick sand-cement blocks, and that the roof will be 8.7 meters long and 3 meters wide, with a pitched design. If the site selected for the building is soft, dark soil that can support 4,900 kg/sq. meter, can the building be constructed as planned?

Here are the calculations:

Equation 1

Weight per square meter = [ weight of longest wall (kg) + weight of roof supported by longest wall (kg) ] / length of longest wall

STEP 1. Enter the length of the longest wall in Equation 1:

Equation 1

STEP 2. Calculate the weight of the longest wall.

(a) Use Equation 2:

(b) Use Table A, page 203, to find the wall's weight per square meter for every centimeter of wall thickness.

The building's walls will be made of sand-cement blocks which Table A says weigh 75 kg/aq. meter for every centimeter of wall thickness.

(c) Multiply the figure you find in Table A by the thickness of the building's walls. The result will be the weight of 1 square meter of wall. Enter this answer in the correct place in Equation 2.

The sand-cement blocks that will be used will be 20 cm thick. So a wall made of these blocks will weigh 75 kg/sq. meter x 20 cm thick = 1500 kg/square meter.

Entering this answer in Equation 2:

(d) Multiply the length of the longest wall in meters by its height and enter the result in the correct place in Equation 2.

The longest wall of the building will be 7.5 meters long and 2.4 meters high. 7.5 x 2.4 = 18 square meters.

Entering this answer in Equation 2:

(e) Compute the weight of the longest wall based on the figures you have entered in Equation 2 in steps 2(c) and 2(d).

1500 kg/sq. meter x 18 sq. meters = 27,000 kg. Entering this result in Equation 1:

STEP 3. Estimate the weight of the roof supported by the longest wall.

(a) Use Equation 3:

Equation 3

(b) Use Table B. page 204, to find the estimated weight of the roof per square meter. Enter this figure in the correct place in Equation 3.

The roof is planned with a pitched roof that Table B says will weigh about 170 kg/sq. meter.

Entering this answer in Equation 3:

(c) Multiply the length of the roof by its height to find the number of square meters of roof space planned. Enter this figure In the correct place in Equation 3.

The roof is planned to be 3 meters wide and 8.7 meters long. am x 8.7m = 26.1 square meters.

Entering this answer in Equation 3:

(d) Compute the weight of roof supported by the longest wall using the figures you have entered in Equation 3 in steps 3(b) and 3(c).

170 kg/sq. meter x 26.1 sq. meters = 4,437 kg. Entering this result in Equation 1:

STEP 4. Calculate the weight of the building per square meter, using the figures you calculated in steps 1, 2(e), and 3(c) and Equation 1.

The building will weigh approximately 4,191 kg/sq. meter.

STEP 5. Compare the building's estimated weight/square meter with the weight-bearing capacity of the soil at the site. Use Table C, page 205.

According to Table C, the weight-bearing capacity of the soft, dark soil at this site is 4,900 kg/sq. meter. Since this building will weigh only 4,191 kg/sq. meter, the building can be built safely at this site.

To determine whether the soil at any proposed site will support a planned building, all the builder needs to do is substitute the figures for his/her building and site in the step-by-step equations on pages 202-205, as shown.