Demolition of buildings

Demolition means dismantling, razing, destroying or wrecking any building structure or any part thereof by preplanned and controlled methods. 

The three things involved in demolition of a building are 

 1. Demolition planning 

 2. Precautionary measures

 3. Methods of demolition

Demolition planning 

Demolition planning includes building appraisal such as survey, structural survey, demolition plan and stability report including calculations. Termination of utilities. Planning for handling hazardous materials. 

Prior to carrying out any building demolition, detailed building appraisal by means of surveys and appropriate assessments shall be required. In general, the surveys shall include a building survey and a structural survey with photographs or videos taken for future reference. Based on the findings of these surveys, a demolition plan shall then be prepared. 

Building survey 

The building survey shall cover the following 

 1. The construction materials 

 2. The existing use and if possible, the past uses of the buildings prior to demolition

 3. The presence of wastewater, hazardous materials which can contribute to air pollution and soil contamination

 4. Potential dangerous areas. Example: abnormal layouts, presence of enclosed voids, and non ventilated light wells which may trap obnoxious gas at the bottom.

 5. Adjoining properties and site conditions 

 6. Drainage conditions and possible problems on water pollution, flooding and erosion

 7. Shared facilities with adjoining building, including common staircases, party walls, and the adjoining buildings, during demolition.

 8. Hoarding and covered walkway requirements.

 9. Adjoining pedestrian and vehicular traffic conditions. 

 10. Available headroom, clear spaces and distance of building from lot boundary which may affect the loading operation and transportation of building operations and transportation of building debris during demolition 

 11. The sensitivity of neighbourhood with respect to noise, dust, vibration and traffic impact

 12. Available site area to allow on site sorting of building debris

Structural survey 

The structural survey shall cover the following 

1. The structural material used 

2. The original structural system employed in the design 

3. The method of construction

4. Degree of deterioration on any structural members

5. The structural condition of adjoining structures and its shoring which may be affected by the proposed demolition work 

6. The presence of continuous structures that may be truncated by the demolition

7. The structural system and structural condition of basements underground or underground vaults 

8. The presence of exposed bracing or possible presence of covered bracing

9. The nature of walls whether it is blockwall, reinforced concrete walls, load bearing walls  or partition walls

10. Cantilevered structures such as canopies, balconies, or other forms of architectural features

Demolition plan 

A demolition plan shall include the following 

    A plan showing 

a) The location of the building to be demolished 

b) A detailed topography of the site and its surroundings 

c) The distances from the building to be demolished to its adjacent buildings, streets, structures 

    A layout plan of all floors of the building to be demolished with adequate sections showing  

a) The occupancy usage of the floors 

b) The structural support systems 

c) The principal material of construction 

d) The condition of the building e.g. the degree of deterioration, and 

 e) The relationship of the building to be demolished with neighboring properties affected by the demolition 

A plan showing the structural arrangement and construction of all unconventional structural elements such as prestressed concrete structures, precast concrete members, stressed skin structures, steel framed structures hanger, hanging ties, trusses or vierendeel grinders, deep beams, long span beams, arches, transfer plates, transfer grinders, earth retaining or basement structures, building which also act as earth retaining structures supporting adjacent ground, flat slabs, hollow block ribbed slabs and large cantilever structures.

 A plan showing the procedure for the demolition of the building detailed sequence of demolishing particular structural members and the method of demolition to be adopted including the restrictions on the use of any particular type of equipment. 

Precautionary measures 

1. Erecting of hoarding and covered walkway 

2. Scaffolding and screen covers 

3. Catchfan 

4. Temporary supports 

5. Protection of properties

6. Protetion of traffic

7. Special safety of considerations 

8. Environmental precautions 

9. Debris and waste handling 

Methods of demolition 

1. Top down manual method 

2. Top down by machines 

3. Mechanical method by hydraulic crushed with long boom arm  

4. Wrecking ball 

5. Implosion 

6. Other methods : non explosive demolition agents, saw cutting, cutting and lifting mechanical demolition, thermal lance, water jet.