· Concrete Decks/Slabs- Generally called asslabs, they are mostly used for flat roof. This can be cast insitu orprecasted.
They are available in both RCC and pre stressed concrete. They arenot often used for sloped roof but mainly for carrying heavy loads like openterrace where often people will be using it for sitting. Not recommended forpitched single floor buildings.· Steel Decks- They are wide panels of metalswhich can be directly used without shingles. They are to be welded to steelsupports if the deck is to transfer loads to sheer walls or columns. One of themain disadvantage of this roofing is that it has very low R- Value (thermalresistance) and a good insulation layer has to be provided to compromise it.They are generally used for industrial buildings and economical residentialbuildings.
Cost of installation depends on the quality of material opted and itcan be cheap. It is very easy to install.· Wood- comes in different types like wood boardsand plywood.
Plywood are made of thin layers of wood adhere together such thatgrain of each layer is perpendicular to adjacent layers. This gives greaterstrength and stability to its dimension. Wood Boards can also be used insteadof plywood.
But the main problem with the wood is they can swell and shrink ifit absorbs moisture. This can be caused by lack of ventilation in the building.An extra layer of thermal insulation is to be provided in between roof deck andshingles· Structural Insulated Panels- SIPs are made fromsandwiching 3 layers of structures.
They have the same strength as a wood deckcan have. The two outer layers are usually made of oriented standard boards andthe core layer is an insulation layer generally made of different materials bydifferent manufacturer. Some of the used core material are Expanded PolyStyrene, polyurethane, polyisocyanurate.
Polyisocyanurate has the best insulationproperty. Many other insulation materials are available, each with differentheat resistance, fire resistance and cost. They are eco-friendly, have goodstrength, cheaper than plywood, has good moisture resistant and easy toinstall.
Bycomparing the all the available deck materials in Europe SIPs prove to be goodchoice as it can act as both roof deck and also a thermal insulator. For othertypes of deck an extra roof rigid insulation is to be provided. So SIPs suitsbetter to an Earthship.