The approach adopted for the survey included the following:

A walkover survey was undertaken in the various communities with the community representatives, during which the types, number and general fabric makeup of the structures were observed. Courtesy calls were made on the community elders to announce the presence of the survey team and set dates for broader stakeholder consultations prior to commencement of the actual survey.

A meeting, comprising the community leaders was held to explain the methodology of the project and seek the consent of the communities for the project and the convenient day to start the survey.

Each building was surveyed using a Building Structural Survey form designed to capture all relevant information on the building. The information requested on each form consists of:

A thorough inspection was conducted on each of the buildings and included looking at structural elements like foundations, walls, floors, roofs, windows, and doors. High-resolution photographs of every critical area of the buildings were taken to document pre-existing conditions such as cracks, settling, and any visible defects, timestamps were ensured for these photographs. A crack map of each of the buildings were created showing the location, length, and width of cracks in walls, ceilings, floors, and other parts of the building.

Most of the buildings were residential, engineered with proper foundations and some are also non-engineered without proper foundations to support the structure. Figure 1 shows the distribution of wall fabrics in the communities, the dominant wall fabrics are the sandcrete blocks. The most used materials for wall plastering are cement/sand mortar; some landcrete structures were not plastered exposing the buildings to erosions on the walls and the foundation level. Predominant roofing type was the corrugated iron sheets and a few thatch roofs located in the remote areas. The doors and window are made of wood, glass and metal. Table 2 and Figure 2 show the age distribution of wall fabrics in the communities.

Four types of building walls were identified in the communities, landcrete, sandcrete, cement rendered landcrete and wooden walls. The existing defects on the building walls are described according to the building walls below.

Major building material used in its construction is the earth material. The commonest defects identified are the crocodile skin crack. These cracks usually originate from the shrinkage of clay in the earth material. The floors were made of rammed earth which had resulted in very deep cracks on the building floors. Through cracks can be located on both the interior and exterior surface of the walls; it cut through the walls to the other side. There were also vertical, horizontal, diagonal cracks on the building walls. The foundations of these buildings have been eroded by rain. A typical landcrete structure with associated defects is shown in Figure 3 .

These buildings types have been constructed with earth material and are similar to the landcrete building but the walls have been rendered with cement mortar. Defects associated with these types of buildings spalling-off of the mortar from the walls due to improper bonding between them and different water absorption rates ( Figure 4 ). Tiny hair line cracks were observed on the rendered surface. Vertical and diagonal surface cracks exist in the mortar plaster on the adobe and wattle and daub walls. The cracks originate from the corners of doors/window frames and propagate either downwards towards the ground or upwards towards the support of rafters on the walls. Horizontal cracks are identified at the edges of the door frames. Figure 5 shows vertical through on a cement rendered landcrete wall.

Defects associated with these structures include all the major cracks: surface cracks, horizontal cracks, vertical cracks, through cracks and diagonal cracks. Older buildings (>10 years) were predominant with vertical through cracks from the door frames to the gable level. Surface cracks which were mostly located at the plinth level of the structure appeared to have been caused by persistent movement of rain water around the foundation and the rise of water table resulting in the wetting of the walls by capillary action of the walling material. Defects on the new structures were few and in most cases no defects were identified. Figure 6 & Figure 7 are typical defects found on sandcrete structures.

These are structures constructed with wooden material, mini shops, local restaurants (chop bars), bathrooms, toilets are the main structures constructed with wooden materials in the community. The only defects associated with these structures were the deterioration of the wooden structure due to environmental factors and termite infestation. Where the floors of the structures were made with cement/sand mortar, cracks exist. Figure 8 illustrates a typical deteriorated wooden structure.

Development of defects such as cracks on structures can be attributed to many factors. Observations made on the defects during the survey suggest that the defects may be caused by:

Soils used for landcrete construction has high clay content. Since clay is an expansive soil, seasonal variation in the moisture content causes expansions of the materials thereby inducing cracks in the building. Wattle and daub wall constructions, when not covered externally by earth/cement mortar plaster have been shown eroded by driving rain. Combination of building materials used in the construction are susceptible to chemical reactions. The combination of cement and Atakpame can result in a reaction between sulphate from the earth material and cement. Cracks develop at the joint between cement and the earth material.

Most of the building walls were constructed with a foundation depth of less than 450 mm. The very thin floor screed covering and the construction method of compacting the interior floors (however poor the compaction) after the wall has been built has led to the cracks in the floor screed, spalling-off of screed cover and the separation cracks between the wall and the screed. These conditions are bound to worsen with increased human traffic on the floors and any movement.

Differential settlement of the foundation soils on loose, soft and highly compressible soils where the load imposed from the foundation overstress the soils supporting the foundation. Cracks caused by differential settlements are vertical in orientation and runs from the foundation level to the lentil.

Seasonal changes in weather conditions had caused deterioration in the building wall fabric and other structural members which initiate defects. Erosion of the foundation and plinth positions of the walls leading to hanging buildings has been observed and indeed is persistent in the communities. Unplastered landcrete walls have also been washed away by driving rain.

Building defects tend to worsen with the age because all building materials deteriorated with age. Regular and/or effective building maintenance will slow such a process. However, with the exception of rebuilding as a result of building collapse and painting, very little maintenance is evident in the buildings surveyed except the occasional attempt to patch up large through-wall cracks. The results of such attempts have not been very successful because the materials employed for repair, the methods adopted or the severity of crack in the parent wall are such that not very much could be achieved.

The roots of trees located in the vicinity of a wall can create cracks in walls due to growth of roots under foundation. The cracks occur in clay soil due to moisture contained by roots.