ROOF EXTERIOR
The roof exterior can be tricky to closely inspect without getting onto the roof. Accessing the roof is a potential safety hazard, especially on a taller building like an apartment building,  warehouse or factory, and I would not recommend it unless you are a professional with the right gear and insurance. Many roof defects can be detected from the interior and from the ground. I suggest you inspect the roof from the ground only and leave the full roof inspection in Brisbane, Gold Coast or Ipswich of up to an experienced Building inspector like BuildingPro.

Metal sheet roof
If possible, get to some high ground from where you can view the roof. If the roof is a metal sheet type of roof, the biggest concern will generally be rust. If there are areas of rust, the rust can cause holes in the roof that allow water penetration. Sometimes the rust is visible from the ground as brown patches. Often the most significant rust occurs where roof sheets overlap, and this is not easy to see from the exterior.  sometimes rust is caused on commercial buildings by air conditioning condensate overflows discharging onto the roof.  If the roof is the original roof, and access is difficult from the ground, then ask the building inspector to check it from inside the roof.
Generally, a metal roof will last for about 50 years, so if the building you keep up the maintenance. A leaky roof on a commercial building is very common because it will have a lot of roof penetrations that all have the potential for the flashing to fail and leak.

Metal sheet roofs on Houses and Commercial properties
If possible, get to some high ground from where you can view the roof. If the roof is a metal sheet type of roof, the biggest concern will generally be rust. If there are areas of rust, the rust can cause holes in the roof that allow water penetration. Sometimes the rust is visible from the ground as brown patches. Often the most significant rust occurs where roof sheets overlap, and this is not easy to see from the exterior. If the roof is the original roof, and access is difficult from the ground, then ask the building inspector to check it from inside the roof.
Generally, a metal roof will last for about 50 years, so if the building you are looking at is more than 50 years old, the roof should not be the original roof. If it is the original, it may need to be replaced. The average cost of replacing a roof on a single-storey house of around 100m2 is $15,000 or more.  On a Commercial building like a factory or warehouse, the roof replacement could be $50,000 or more depending upon the size. Make sure you refer this to your Building inspector in Queensland.

WARNING ABOUT LEAD CAPPED NAILS ON RESIDENTIAL AND COMMERCIAL ROOFS
Roof nails of house, factories, child care centres, shops, offices and other building types often have lead caps on them. The lead can leach into the rainwater that runs off the roof, so don’t drink rainwater collected from a roof that has lead-capped nails.

Case Study – Hail damaged roof in Brisbane
I recently inspected two new blocks of townhouses and found both blocks had hail-damaged roofs. The real estate agent and builder had not disclosed their knowledge of this matter to the purchasers. The cost to replace an entire roof would have to be claimed on the body corporate insurance as the buildings were complete. To rectify this defect, scaffolding would need to be erected around the entire building, the old roof would need to be removed and a new roof installed. The body corporate would need to fund the excess on the insurance claim and each owner may also have to pay an increased premium each year as a result of the body corporate making such a huge claim.  Brisbane and South east Queensland is known for hail storms so make sure you have this checked by your Building inspector.

Metal roof tiles
Metal roof tiles are tiles that look like concrete tiles from a distance, but upon closer inspection, you can see that they are metal. These were popular in the 1980s. Metal tiles are flimsy and if you don’t step very lightly in soft-soled shoes right above the tile batten they will dent.  It’s rare to see metal roof tiles on a commercial property inspection in Queensland.

WARNING
It is not uncommon to find metal tiled roofs that have a large number of dented tiles. It can be difficult or impossible to find matching metal tiles and sometimes the entire roof has to be replaced.
Most of the clients I inspect for have no idea that the house they are buying has a metal tile roof. The single-storey, tenanted houses always have the worst damage because tenants do not seem to notice the damage they are causing when they get on the roof, for example, to retrieve a lost cricket ball or adjust the TV antenna.

Concrete tile
Concrete tile roofs have capping tiles at the ridges, hips and gables that are wired onto the frame, secured and waterproofed with mortar. This is known as ‘bedding’ and ‘pointing’. Over time, bedding and pointing can become cracked and loose, and this allows water penetration. The cost to repoint an average-sized tile roof of a house is $2,200 or more.”

Terracotta tile
Terracotta tile roofs are the orange-coloured tile roofs. These roofs are long-lasting and attractive, but they are more prone to leakage in heavy rainfall as the gaps under the tiles can allow wind-driven rain to enter the interior and cause minor damage to the ceiling. The lichen that grows on terracotta tile roofs is generally harmless and can be removed with pressure cleaning if a cleaner appearance is desired.
Tiled roofs of houses and commercial properties will have a life expectancy of approximately 60 to 100 years plus. Terracotta tiles last longer than concrete tiles. Terracotta tiles can be prone to pitting. This problem is known as ‘fretting’ and it manifests itself by leaving small piles of tiny flakes and grains of terracotta on top of the ceiling inside the roof void. Over time, the fretting can become so severe that some of the affected tiles need to be replaced.

WARNING ABOUT ROOF REPLACEMENT IN QUEENSLAND

Remember that if more than 20% of the roof is replaced in Queensland then the roof framing needs to be brought into compliance with the National Construction Code.  This includes insulation, sarking, bracing and tie-downs.  This can add a substantial cost to a re-roof project and if overlooked it may be noted by a pre-purchase building inspection and the consequence is that the roof may need to be removed (this could also require scaffolding to be erected) and then the roof framing brought into compliance and roof re-installed.  Don’t be caught out on your residential or commercial building inspection in Brisbane – make sure a new roof has a Building Approval and meets the current code by having a. professional building and pest inspection.