Pre Purchase Building Inspections – Moisture Ingress and Structural Defects
Moisture can enter a residential property through a myriad of different sources; the question in relation to pre purchase building inspections is will it ever amount to a major structural defect? The answer is likely to be no.
- What is moisture ingress?
Keeping the habitable areas of a residential building dry and free from moisture is a key component of the Australian Building Code. Notwithstanding, water and hence moisture can find its way into the building from a myriad of different sources. These can include:
- Holes and gaps in roof covers and associated flashings allowing stormwater to enter the building
- Faulty or blocked roof plumbing
- Lateral damp from soils, mulch and vegetation in close proximity to external walls
- Underground rooms (cellars, theatres, storerooms etc) and lateral damp from adjacent soils
- Rising damp
- Failure of waterproofing membranes in shower stalls, wet areas, balconies below ground areas and pools/ponds
- Leaking pipes and or plumbing fittings
- Single leaf masonry walls
- Poor ventilation
In short, all of the above can result in moisture entering or being retained within a building.
2. Structural Defects
Most pre purchase building inspection reports on residential properties in WA are undertaken in accordance with AS 4349.1 which defines a range of criteria for major defects. Appendix A refers specifically to structural defects, and most importantly defines what needs to be excluded when considering structural defects. In particular the Standard Notes:
Serviceability damp defects such as condensation, rising damp, lateral damp, falling damp should only be assessed and reported on where structural damage has occurred, is occurring, or may occur (e.g., fungal rot) significant spalling of masonry or concrete structural elements, significant fretting of mortar, rusting of primary structural elements. Stormwater drainage and surface water defects commonly cause or exacerbate foundation instability and these issues should be assessed and reported on where relevant.
In essence, the presence of moisture is unlikely to be a major structural defect however; the presence of moisture in the long term may contribute to a major structural defect emerging. For example, high levels of moisture in a concrete balcony may be identified, the issue in itself will not be a major structural defect. However, over many years the high levels of moisture in the balcony slab may contribute to the rusting of the steel in the slab (concrete cancer) which may become a major structural defect. The key issue here being that the existence of the moisture is not the major structural defect but the resultant concrete cancer might be a major structural defect.
3. Moisture ingress and Major Defects
A building inspector may consider high moisture levels to be a major non-structural defect as defined by AS 4349.1 but not a major structural defect. Using the above, the inspector may identify that there are high levels of moisture in a balcony concrete slab, but the slab itself remains structurally sound, at the time of the inspection.
4. So what does all of this mean to the Pre Purchase Building Inspection Reports
It is quite possible that during a pre purchase building inspection, moisture ingress into a residential building will be identified. The source of the water can be quite diverse as described.
Ideally, moisture should be kept out of habitable areas. When it is identified it should be remediated. In some cases excess moisture might be classified as a major non-structural defect indicating a degree of urgency to remediate the issue.
Where a property is being purchased in accordance with the WA REIWA pre purchase building clause which is based on AS 4349.1 major structural defect will generally relate to the sub floor frame or concrete slab, load bearing walls and roof frames. The balance of the building elements are unlikely to be structural elements. Even if the structural elements contain elevated moisture levels it is unlikely that the elevated moisture will be considered a structural defect.
For Sellers If elevated moisture levels are identified in structural elements in a property being sold, it is unlikely to be a major structural defect requiring remediation by the seller, if the REIWA pre purchase building inspection clause has been utilised.
For Buyers If elevated moisture levels are identified in structural elements in a property being purchased, it is unlikely to be a major structural defect requiring remediation by the seller, if the REIWA pre purchase building inspection clause has been utilised. The buyer should consider remediating the issue post settlement as the issued can develop into a more significant problem if not addressed.
The above views are consistent with those expressed by The Industry Association of Building and Property Inspectors in WA Inc.
October 2019
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