00:00 "Identifying Common Issues with Low-Pitched Roofs
00:51 What is a head-lap ?
01:52 Eaves protection incorrectly installed
03:06 Cavity wall open or closed?
04:09 Tiled roof insulation and venting incorrect
04:41 Thermal bringing to the ceiling
05:46 No insulation in cavity wall!
07:00 Water leaking through sarking felt
08:08 Incorrect pitch of roof
08:32 Sarking felt incorrectly installed
09:16 Venting and condensation
09:50 Skylights
In this video, I highlight several observations during a roof survey conducted in the rain. The inspection revealed multiple issues, particularly with the low-pitched roof. I'll discuss the felt and other elements, highlighting insights that only became apparent due to the rain.
At the top left-hand side of the roof, you can see water movement linked to capillary action. Water is being drawn up under the tiles because they were installed incorrectly. Specifically, the tiles on this low-pitched roof have been laid too flat. These interlocking tiles should not be installed at an angle below 17.5 degrees. The headlap, which is the overlap between rows of tiles, is insufficient.
The headlap is crucial to prevent water ingress. On a low-pitched roof, proper headlap is even more important. For a roof at 17.5 degrees, you need a headlap of at least 100 mm. However, on this roof, the headlap is only about 70 to 75 mm, which is a major reason for the leaks, leading to my involvement for this roof survey.
Regarding the sarking felt, it’s important to remember that it acts as a secondary defence, not the primary barrier. Sarking felt should channel any water that gets past the tiles into the gutter. Unfortunately, the eaves protection system wasn't installed properly here, causing water to pool behind the eaves rather than drain away. This pooling water led to significant issues, especially around nail penetrations, which allowed water to leak through.
Using a camera, I inspected inside the roof. I found an open cavity that should have been sealed to prevent rising moisture. On this low-pitched roof, ventilation was poorly executed, allowing both cold air and moisture to enter. Properly sealing this cavity would help prevent moisture issues.
The insulation was also improperly installed. Gaps in the insulation created thermal bridging, allowing cold air to enter and increasing condensation risk. When insulation in the wall doesn’t connect to the roof insulation, it leads to inefficiencies and condensation issues.
The flashing along the walls also had issues. Though it appeared neat, it wasn’t secured correctly, lacking clips to hold it in place, which increased wind uplift risk. Water was also able to get under the flashing due to capillary action. With a roof pitch of only 10 degrees, it’s particularly vulnerable to water getting underneath.
Another problem was that the sarking felt didn’t extend up the wall behind the flashing. Ideally, the felt should go up behind the wall, and a batten should be installed to stop it from flapping. In previous jobs, I’ve glued the felt up the wall to make it waterproof, but unfortunately, this wasn’t done here.
The skylights on this roof, while aesthetically pleasing, are essentially double-glazed windows on a low-pitched roof. They lack proper framing and drip details needed for water management. Given the roof's low pitch, water can easily become trapped behind the skylights and enter through capillary action. I plan to make a separate video on this common issue.
Finally, there was oxidisation at the back of the lead flashing. This is typical when lead is exposed to moisture, but proper ventilation is necessary to allow moisture to escape. The lack of ventilation here could lead to rust and further damage.
This video highlights common problems from poor installation on a low-pitched roof. These mistakes are avoidable with proper techniques and adherence to building standards. If you have any questions about roof surveys, low-pitched roofs, or the issues discussed, please get in touch.
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