Norwegian Pitched Roof Defects
Abstract
:1. Introduction
1.1. Wood Building Traditions and Climate Exposure
1.2. Building Defects and Robustness
1.3. Objective and Scope
2. Pitched Wooden Roof Constructions
2.1. Design Principles
- (1)
- moisture from the roof, and thus prevent mould growth and other moisture damage; and
- (2)
- heat, and thus prevent unwanted melting of snow and ice at the eaves and gutters.
- Pitched wooden roofs with separate wind barrier and underlayer roof (ventilation air cavity between wind barrier and underlayer roof).
- Pitched wooden roofs with combined underlayer roof and wind barrier (watertight vapour open membrane).
- Pitched wooden roofs with cold attics.
- Pitched wooden roofs with heated rooms in parts of the attic.
2.2. Type A—Pitched Wooden Roof with Separate Wind Barrier and Underroof
- raintight roofing;
- drainage and ventilation cavity;
- vapour-tight underlayer roof;
- ventilation cavity; and
- vapour open wind barrier.
2.3. Type B—Pitched Wooden Roofs with Combined Wind Barrier and Underlayer Roof
- raintight roofing;
- drainage and ventilation cavity; and
- combined vapour open and watertight wind barrier and underlayer roof.
2.4. Type C—Pitched Wooden Roofs with Cold Attics
- (a)
- Cold, ventilated attic space with air stream flowing through the attic itself. The underlayer roof may be vapour tight. There are ventilation openings in the ridge and between the underlayer roof and the thermal insulation along the eaves of the building. Ventilation openings have to be designed in order to avoid penetration of snow and rain into the attic. Only the vapour retarder contributes to the airtightness of the building (ceiling), making the solution vulnerable to holes and imperfections in the vapour retarder, which again can cause condensation because of air (containing moisture) leakages through the construction. Hagentoft et al. [15] found that the moisture level of cold ventilated lofts is improved if the attic floor is airtight, has low built-in moisture content, and has well-ventilated indoor air.
- (b)
- Cold, unventilated attic space with all ventilation between the underlayer roof and roof covering. The construction is a further development of a) and an improved roof design. The underlayer roof is a vapour open and watertight wind barrier. Both the wind barrier and vapour retarder should be used continuously, thus making it easier to ensure airtightness of the building.
2.5. Type D—Pitched Wooden Roofs with Heated Rooms in Part of the Attic
- (a)
- Thermally non-insulated ventilated attic. The underlayer roofing can be vapour tight. There are ventilation openings in the ridge and between the underlayer roof and the thermal insulation along the purlin of the building. Ventilation openings have to be designed in order to avoid penetration of snow and rain into the attic. The vapour retarder and wind barrier are not continuous through the floor construction and the roof is therefore particularly vulnerable to moisture damage due to air leakages.
- (b)
- Thermally insulated non-ventilated attic. The underlayer roof has to be vapour open. The construction is a further development of a) and an improved solution. It is possible to make a continuous and airtight joint between the wind barrier on the wall and the underlayer roof, thus making the construction more resistant to moisture compared to a).
3. Analysis of Norwegian Roof Defects
3.1. SINTEF Building Defect Archive
3.2. Building Defects Versus Source of Defect
3.3. Typical Damage and Defects
4. Discussion
4.1 Type A—Pitched Wooden Roofs with Separate Wind Barrier and Roofing Underlay
4.2 Type B—Pitched Wooden Roofs with Combined Wind Barrier and Roofing Underlay
4.3 Type C—Pitched Wooden Roofs with Cold Attics
4.4 Type D—Pitched Wooden Roofs with Heated Rooms in Part of the Attic
5. Conclusions
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Selection | Total Number of Defect Cases | Precipitation (%) | Indoor Moisture (%) | Built-in Moisture (%) | Water in Soil (%) | Leakage Water (from e.g., Sanitary Installations) (%) | Combinations of Moisture Sources (%) | Sources of Moisture in Combination with Other sources (%) | Other Sources (not Moisture Related) (%) (2) |
---|---|---|---|---|---|---|---|---|---|
Total amount of building defects | 2423 | 24 | 15 | 6 | 8 | 5 | 9 | 9 | 24 |
Total amount of roof cases | 465 | 49 | 24 | 1 | 2 | 0 | 12 | 3 | 9 |
| 83 | 51 | 22 | 2 | 0 | 1 | 13 | 2 | 8 |
| 121 | 78 | 8 | 1 | 5 | 0 | 4 | 2 | 2 |
| 186 | 33 | 34 | 1 | 1 | 0 | 16 | 3 | 12 |
| 33 | 33 | 42 | 0 | 0 | 0 | 12 | 3 | 9 |
| 32 | 50 | 28 | 0 | 0 | 0 | 19 | 0 | 3 |
| 58 | 34 | 24 | 0 | 1 | 0 | 16 | 5 | 19 |
| 63 | 24 | 41 | 2 | 1 | 0 | 16 | 3 | 13 |
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Gullbrekken, L.; Kvande, T.; Jelle, B.P.; Time, B. Norwegian Pitched Roof Defects. Buildings 2016, 6, 24. https://doi.org/10.3390/buildings6020024
Gullbrekken L, Kvande T, Jelle BP, Time B. Norwegian Pitched Roof Defects. Buildings. 2016; 6(2):24. https://doi.org/10.3390/buildings6020024
Chicago/Turabian StyleGullbrekken, Lars, Tore Kvande, Bjørn Petter Jelle, and Berit Time. 2016. "Norwegian Pitched Roof Defects" Buildings 6, no. 2: 24. https://doi.org/10.3390/buildings6020024