building construction Paper 2 WASSCE (PC 2ND), 2018

Question 2

 

(a) State three reason why it is necessary to remove a vegetable soil from a building site.

(b) Explain one reason for providing a concrete foundation to a load bearing wall.

(c) Sketch a cross-section through a raft foundation and label the following parts.
(i)  ground beam;
(ii) reinforced concrete.


Observation

 

A good number of candidates were able to:

- state the reason why it is necessary to remove a vegetable soil from a  building site.
- explain one reason for providing a concrete foundation to a load bearing wall.

 

However, many of them failed to sketch a cross-section through a raft foundation and label the following parts.
(i) ground beam;
(ii)reinforced concrete.

 

The expected response to question 2 is as given below:

 

2(a)  Reasons why it is necessary to remove vegetable soil from a building site:

 

  • to prevent instability of the building;`
  • to prevent unreliable bearing capacity of the imposed load;
  • to prevent organisms and chemicals necessary for the growth of plants or
  • to prevent the growth of plants underneath the ground floor of a building;
  • to prevent settlement.     

                                                                                       
(b) Reason for providing a concrete foundation to a load bearing wall:

- is to spread all the load from the building over sufficient areas of the soil to avoid undue settlement;
- is to provide a solid base for the wall.        

(c) Sketch of a cross-section through a raft foundation and labelling of the parts: