A conventional roof framework is a solid structure, resting on walls on a strong foundation. A roof may be a reinforced concrete slab. However, most Calgary roofs slope so as to more easily shed rain or snow. We discuss reasons why some conventional roofs sag, and what a roofer can do about this after it happens.
The Parts of a Conventional Sloping Roof
A conventional, sloping roof comprises several layers, most of which are not normally visible:
- A system of robust rafters – usually wood but sometimes steel – determining the shape of the roof.
- A series of lighter strips laid over the rafters in a pattern to support the roofing material itself.
- A waterproofing underlay placed over the lighter strips which forms a secondary defence against leaking.
- The roofing material, which is the primary defence and creates a particular architectural impression.
That Sounds Solid – Why Do Some Roofs Still Sag?
All roof surfaces sag slightly as they age. This is due to the weight compressing the supporting materials, and is seldom cause for concern. However, if they dip down further than a critical point, the waterproofing will begin to fail. Although this does not necessarily indicate a new roof.
The Outer Surface of the Roof Could be Leaking
The top covering of a roof – shingles, tiles etc. – is the primary waterproofing defence. Tiny gaps between individual sheets can admit moisture, causing mold and mildew. This can weaken the roof framework causing it to sag.
The Roof May Be Too Heavy for the Structure
A competent roofer designs the rafter structure to support the weight of the covering. If a new roof sags, they got their calculations wrong. However, if an old roof starts sagging, this may be due to excessive accumulation of snow.
The Roof May Simply Be Getting Older
Timber is an organic material, and may eventually lose its tensile strength. Gradually shifting foundations may also take their toll. These factors depend on the skills of the designer and builder. That’s why we say quality could cost you more.
How Valiant Exteriors Tackles Sagging Roofs
A sagging roof – within limits – does not always require replacement. There may be things Valiant Exteriors could do to improve the situation. However, this is not something we can discuss over the phone. We really do need to physically inspect your roof, before we can advise what’s best to do. Please be in touch if we could help.
More Information
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Ruined Building Revealing Typical Roof Structure (Tomasz Sienicki BY CC 3.0 Unported)