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Roof covering-slideshare

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Roof covering-slideshare

  1. 1. Roofs 2Roof coverings and insulation
  2. 2. Covering the roofThe structure is complete. Now you need tokeep the rain out and the heat in…
  3. 3. Roof coverings• Pitched roofs – Rely on gravity to move the water down the slope – Coverings keep the rain out by overlapping• Flat roofs – Water may stand on a flat roof, so the covering has to be completely water tight.
  4. 4. Pitched roof coverings• Can be anything from sheet lead to thatch• On new conventional houses, the most common coverings are: – Double overlap slates and plain tiles – Single overlap interlocking tiles• In both cases, coverings are supported by battens on a “sarking layer”
  5. 5. Sarking and battens fixed to each slope
  6. 6. Sarking and battens fixed to each slope
  7. 7. Sarking and battens fixed to each slopeSarking layer, akaunderslating. Ideallybreathable but waterproofSarking should sagbetween rafters andproject into gutter ateaves
  8. 8. Sarking and battens fixed to each slopeSarking layer, akaunderslating. Ideallybreathable but waterproof Battens: softwood, treated against decay.Sarking should sag Nailed to raftersbetween rafters and through sarking andproject into gutter at nailed to top of gableeaves wall
  9. 9. Examples of battening outThis example is unusual. Sarking andbattening are normally completed beforeslating starts. This is an old roof beingrelaid under cover of a temporary roof
  10. 10. Slating. Vertical joints staggered, all slates double lapLook at the text booksfor details!Every row is nailed toa batten Double overlap
  11. 11. Plain tiles: clay or concreteBack of a plain tile:projecting nibs hook overthe batten. Only everythird row needs to benailed
  12. 12. Interlocking tiles: clay or concrete, single overlap, much lighterThe edge of one tileoverlaps andinterlocks with theedge of the next
  13. 13. Ventilate the roof through the eaves and ridgeEssential to maintain ventilation ofthe enclosed roof space to avoidcondensation
  14. 14. Ventilating the slope and ridge• The sarking must be pierced to allow the free flow of air but protected from rain penetration• Special tiles can do this at the ridge and in the slope.
  15. 15. Free flow of air within the roof space above ceiling insulation essential Ventilated ridge Slope ventilators Eaves ventilation
  16. 16. Basic insulation of a pitched roof
  17. 17. Basic insulation of a pitched roofFibreglass insulationlaid between joists.300mm recommended
  18. 18. Basic insulation of a pitched roofFibreglass insulationlaid between joists.300mm recommendedVapour barrier onwarm side
  19. 19. Basic insulation of a pitched roof Fibreglass insulation laid between joists. 300mm recommended Vapour barrier on warm sideFree flow of airessential
  20. 20. Flat roof coverings Firring piece on each joistfacia Roof deck and finish to create fall to gutter Roof joists at 600mm centressoffit • Flat roof coverings on the deck can be: – Sheet material, bonded to the deck – Hot or cold liquids, which cure to form a skin. (Only really applicable to a solid concrete roof deck)
  21. 21. Sheet roof coverings• Bituminous felts laid in hot adhesives (tar) – Usually in three layers, finished in gravel or paint to protect from UV radiation• “High Performance” roofing felts on hot tar – Usually two layers. Flexible and self finished• Loose laid reinforced uPVC fabrics, glued to points on the deck. Not common in housing
  22. 22. Alternative felting systemsBase layer being unrolled Detailed work aroundinto hot tar edgeHi performance top layer Torch-on system Self adhesive Hibeing laid performance felt
  23. 23. Insulating a flat roof• This is one of the difficult areas because of the limited volume inside the roof• The two main systems are “warm deck” or “cold deck”• The important thing is to prevent condensation inside the roof space
  24. 24. Warm deck principles: the whole roof void is warm. deck roof void ceiling Roof finishing layers Insulating roof deckWarm ceiling void Vapour barrier
  25. 25. Cold deck principles: ceiling void is cold and ventilated deck roof void ceiling Roof finishing layersInsulation between joists Vapour barrier Void must be ventilated from the eaves Very difficult to achieve in practice

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