Explanatory Notes

Stormwater Management and Ground Grading
HouseCheck inspectors check the efficient management of water from roofs and storm water away from the base of structures. The best way to achieve efficient ground water management is by the installation of a suitable drainage system, or by installing an impervious, properly sloped apron around the perimeter of walls. HouseCheck inspectors will also check that finished outside ground levels (including paving) are at least 150mm lower than inside floor levels. If the outside ground is higher than the floor inside there is a threat of water seeping into the walls above the DPC, resulting in interior damp damage.

Cracks in Walls, Slabs, and Foundations
Most houses in South Africa sooner or later develop wall cracks. Most of these cracks are not serious and can be ascribed to slight settlement of the foundations, mortar shrinkage, or slight roof movement. However, some cracks can be potentially serious and are the result of significant foundation displacement, water penetration, or excessive roof movement. The most common reasons for cracking of walls are:

• Problem soils: Most South African cities and towns are located in areas where so-called “problem soils” occur. These are mostly “expansive” soils (clay) or “collapsible” soils (sandy). In some areas dramatic ground collapse (sinkholes) can occur where dolomitic and limestone rocks are found; this often results in the formation of underground caverns and voids.
• Ground movement and other stresses: The walls and slabs of all buildings are liable to crack at some point due to the movement and stresses to which buildings are continually subjected. Problem soils, inadequate design of foundations, poor roof anchoring and water penetration may worsen the situation.

Types of cracks: HouseCheck inspectors are trained to diagnose the cause of the observed cracks. Crack diagnosis is not an exact science and where doubt exists, then the services of a structural engineer should be enlisted.

• Settlement cracks: occur as the house “settles” onto its foundation, often leaving “stair step” cracks and diagonal cracks extending upwards from window and door lintels in its wake. Cosmetic repairs such as new paint or crack repair will only permanently fix settlement cracks once the structure has fully settled.
• Movement cracks: occur if the house has been built on expansive (clay) soil with poorly designed foundations. “Stair step” cracks and diagonal cracks extending upwards from the window and door lintels in its wake. Cosmetic repairs such as new paint or crack repair will not permanently fix movement cracks problems caused by expansive soil.
• Thermal cracks: big changes in daily temperature changes may result in excessive expansion and contraction of walls, causing vertical or stair step cracks, or plaster cracks.
• Water damage cracks: Water penetrating walls from above (especially through cracks on the tops of parapet walls) will cause cracks lower down as the water seeps downwards through the wall and seeks an exit from the masonry when encountering an impenetrable barrier such as a concrete slab or waterproofing.
• Roof movement cracks: Movement of the roof, where it rests on the wall plate on top of the walls, can also cause wall cracks. These cracks are usually slight and can be seen along the line of the ceiling and cornices. However, the weight and movement of a badly constructed roof can also result in severe structural damage to the walls below. Roof movement generally results from badly braced rafters and trusses which can exert outward pressure on the tops of load-bearing walls. This is known as truss thrust or truss spread. Poor anchoring of the roof to the walls can also lead to roof movement especially in windy areas. Truss uplift can also occur if the top chords of the truss become damp and expand while the bottom chord remains dry.
• Plaster cracks: Cracks in plastered walls are common, especially in older houses. Plaster cracks may result from stresses caused by movement of the brick substrate (see discussion above). Crazing cracks of plaster may also be caused by incorrect plastering techniques or plaster which has been allowed to dry too fast. One of the main reasons for plaster cracking is changes in ambient moisture levels and different expansion coefficients between mortar plaster, bricks, concrete and steel.
• Slab and foundation cracks: The reason why foundations and slabs on the ground crack is usually soil movement compounded by inadequate foundation/slab design and/or construction. Foundation footings and slabs carry the weight of the walls and roof and so cracks in foundations will almost always result in wall cracks also, the incorrect placement and compaction of the fill beneath the concrete slab is also a common cause of slab cracks. Water seeping under foundations (from downpipes or water ponding against structures) increases the risk of foundations sagging. HouseCheck inspectors will check water management around the base of structures. Tree roots close to structures may also cause problems.

Types: Settlement, movement, thermal, water damage, roof movement, plaster cracks.
Severity (NHBRC Criteria):

• <1mm: Very slight (redecoration).
• 1-5mm: Minor (redecoration).
• 5-15mm: Moderate (minor repairs).
• 15-25mm: Severe (extensive repairs).
• 25mm: Very severe (major repairs/rebuilding).

Damp in Walls and Slabs
Where visible damp is observed, HouseCheck inspectors will use a moisture meter to measure and record whether the damp is old damp (where the cause of the damp has been resolved) or active damp (where the cause of the damp is unresolved or unknown). HouseCheck inspectors will use their experience and training to try and determine the probable cause of the damp problem.
Types of damp:

• Penetrating damp is usually caused by roof leaks or water ingress via exterior wall cracks. Other causes may be leaking plumbing; failure of waterproofing on a wall adjacent to a shower or bath; a planter on an external wall; or water penetrating the exterior wall as a result of incorrect exterior ground levels. Further investigation is usually recommended. Damaged areas should only be repaired and decorated once there is certainty that the source of the moisture ingress has been repaired and the damaged area has completely dried out.
• Rising damp is confined to the lower parts of the internal walls area – usually lower than 1.2m. Rising damp is caused by ground water “wicking up” through the masonry due to missing or damaged, damp-proof course (DPC). HouseCheck recommends further investigation and possible remedy by the installation of a physical or chemical damp proof barrier. Damaged areas should not be redecorated until the source of the water ingress has been located and repaired and the damaged area has completely dried out. Damp proofing course (DPC): in modern buildings a plastic barrier installed at the base of walls and in wall openings is the usual method of preventing water from the ground from wicking up into the structures. Many older buildings do not have an effective DPC. Malthoid or slate was used in older buildings used to prevent rising damp. These components can disintegrate over time causing rising damp to become active and visible on the bottom of walls in older structures. It is recommended that a reputable waterproofing company be contracted to evaluate and propose best solutions to repair the rising damp.
• Mold is black fungi spores which grow on walls, ceilings, behind cupboards and in roof spaces thrive in still, moist conditions. Mould is both unsightly and dangerous to the health of those with allergies. Both penetrating dampness and the lack of adequate ventilation in a bathroom or bedroom encourage the growth of mold spores.
• Efflorescence is an aesthetic problem. Efflorescence is a white, powdery salt substance that forms on the surfaces of concrete, bricks and plaster. It is caused by soluble salts migrating through the material via capillary action. Once these soluble salts come into contact with air, unsightly white sediment appears.