There are two main issues for a home inspector to look for when inspecting a wall:
- The presence and significance of wall cracks. A HouseCheck inspector is trained to diagnose what has caused the wall to crack and to recommend remedial action.
Remedial action may range from redecorating for minor cosmetic cracks to a specialist evaluation by a structural engineer, if the inspector suspects that the crack threatens the structural integrity of the building.
- Evidence of damp damage to the wall. A HouseCheck inspector is trained to diagnose what has caused the damp damage to the wall. Damp damage usually manifests itself in blistering or flaking paint, or in the presence of a powdery substance, called efflorescence.
There are a number of possible causes for damp damage to walls, these are discussed below. As a first step the inspector should use a moisture meter to determine whether moisture is still present within the wall. If the wall is dry, then it is possible that the underlying cause of the damp damage was caused either by seasonal rain, or by a water penetration issue which has already been resolved.
The main things the average client (prospective purchaser, or owner of a property) needs to know from the home inspector regarding cracks are:
How serious are the wall cracks?
Generally cracks less than 5 mm wide should not be a cause for concern. However, if such cracks are repaired and then reappear, or begin to widen, this is an indication of continued movement of the structure – indicating a potentially serious problem.
Cracks more than 5 mm wide, or cracks which continue to appear and widen after repair, often indicate a serious on-going problem – pointing to stresses which may eventually threaten the structural stability of a building.
A home inspector who has the training and experience to properly understand the building process, will be better-placed to diagnose the cause of the cracks and to recommend the appropriate remedial action.
Masonry – bricks, blocks, mortar and plaster – is a brittle substance which is prone to cracking under pressure. Most wall cracks are surface cracks in the paint or plaster, caused by poor plastering or painting techniques, and are easily filled and redecorated.
- Surface cracks in the paintwork or underlying plaster usually result when:
- The cement plaster dries too fast. This may result in “crazed” or other fine surface cracks in the finished plaster – because of poor workmanship by the plasterer.
- Bad painting technique or the use of incompatible paints (undercoat and topcoat) may result in fine surface cracks.
- Structural cracks: Wide cracks, or cracks which continue to move, may indicate a major structural defect, which could be expensive to correct.
Not all deep cracks are structural. A “structural crack” is a crack which is affecting, or is likely to affect, the structural performance of its intended function, which is:
- To carry the loads and withstand the forces that the wall was designed to carry;
- To keep out the elements – wind and rain;
- To provide thermal and sound insulation;
- To provide security;
- To be durable.
Deep plaster cracks or cracks which extend through the masonry units may be caused by:
- Foundation failure. Foundations which have not been properly designed to withstand likely ground movement may crack or move (subside or heave) thereby exerting force on the wall above the foundation. Foundations which are undermined by water erosion (from downpipes or stormwater) are also prone to subsidence.
- Roof movement – resulting from a combination of wind and inadequate roof design and roof anchoring.
- Thermal expansion – if adequate control joints have not been provided to accommodate the expansion and contraction of the masonry units in the wall, then thermal expansion cracks may occur. Clay brick wall panels which butt against concrete beams or columns are prone to cracking.
- Nearby trees: Pressure from the roots of trees planted too close to the walls may also be the culprit behind a cracked wall.
- Impact: Doors slamming or other impacts against the wall – could be the cause of some cracks.
- Water ingress into the wall will also eventually result in cracks – often with a tell-tale blackening of mould when the water emerges from the crack
Walls always crack at their weakest point. This is why diagonal cracks extending from the corners of an opening (door or window) are often seen. A V-shaped crack which is wider at the top will usually indicate movement of the wall or foundation below. Cracks can be vertical, horizontal, diagonal or run like a staircase.
Deflection of parts of the wall may also be observed as a result of a crack. “Deflection” means that the planes of the wall on each side of the crack have moved out of the plumb. Deflection may be vertical or horizontal. Deflection is always a sign of a deep crack which may be structural.
Proper evaluation by the home inspector, should determine if further investigation by a structural engineer is necessary. When in doubt the home inspector should always recommend further evaluation by an appropriate specialist.
Recommendations for effective repairs should only be made by the home inspector if this is within the scope and knowledge of the inspector.
Damp damage to walls
There are various causes for dampness and the home inspector should, by a process of careful observation, be able to identify the probable cause of the damp.
Different kinds of damp which the inspector may encounter are:
- Rising damp: This is the process whereby water from the ground rises up from the ground through the tiny spaces within porous masonry or a concrete floor slab.
Rising damp occurs in the absence of an effective waterproof barrier between the soil and the masonry structure. In modern buildings a layer of plastic sheeting placed at ground level is used to provide an effective barrier to prevent rising damp. When strips of plastic are placed under the base of the exterior walls it is called a damp proof course (DPC) and when plastic sheeting is installed between a slab and the ground, it is known as damp proof membrane (DPM).
Rising damp manifests itself close to the bottom of walls as:
- Rotting wooden skirting boards;
- Bubbling or flaking paint;
- Or as a deposit of white salts. This salt deposit is known as “efflorescence”. Efflorescence is the residue of dissolved salts from the ground or masonry which is deposited on the surface of the wall when the rising water evaporates on the surface of the wall.
- Penetrating damp: Water may penetrate into the structure from:
- Roof leaks where the water finds a path into the walls;
- Cracks in the tops of parapet walls and chimney crown which allow water ingress;
- Leaking pipes within walls;
- Poor sealing of the interface between walls and showers, baths, basins and sinks.
- Outside finished ground levels which come into contact with an exterior wall above the DPC. The finished floor level should be a minimum of 150 mm higher than finished ground level. However, landscaping and paving can have the effect of raising the ground levels.
Penetrating damp often manifests with similar evidence as for rising damp – bubbling paint and efflorescence.
If the penetrating moisture surfaces though a ceiling or inside a cupboard then black mould spores may be observed by the home inspector.
With all types of damp, a pin-type moisture meter is the correct instrument for the home inspector to confirm the presence of moisture.
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