acing or restoring the existing roofing, or build a new one. That will usually protect the inside of a house from water damage. Most houses have a problem with the bases of their walls which are not waterproof. The water seeps in the wall from the base, which accounts for the frescoes being more damaged on the bottom portion. There is experimenting being done on rendering the base of the walls safe from water with injections of epoxy, but the usual method is the introduction of lead sheets at the base of the wall that prevent the water from making its way up.Wood was a material widely used for construction in Pompeii and one that was never meant to last for millennia. Since it is often a crucial element of the construction, it must be replaced if the houses and different buildings are meant to stay open to tourists and archaeologists alike. Depending on what essence and where it is used, the replacement wood will last anywhere from three to two hundred years. There are three different categories: contact with ground, without contact but exposed, and without contact and covered. The wood which is in contact with the ground will decay faster because of an increased exposure to water and air. "Without-contact-but-exposed" wood will last longer but not as long as a piece covered by a ceiling or a wall. Wood is chosen according to its density: oak, elm and chestnut have to highest density, while fir and poplar have the lowest. Another thing to consider is in what size the wood can be available; green oak has the highest density, but is very small, so a less dense oak is used which comes in bigger pieces. The price is also an important factor, since the budget for restoration is ridiculously small. Before being used in restoration, the wood is treated to make it last longer and to protect it against insects. A compound of chromium salt and copper is used to dry and preserve the wood, but it leaves the treated piece with a green...
