The steps of the restoration of a building

　　Summaries:Today, when we talk about restoring an old building, many people think it’s a total destruction of the building in order to place a new one. Restoring a building requires a lot of information and skills: be aware that restoring an old house is that with time and patience, take the maximum time to properly analyze the building and the environment in which it is located, seeking to understand the history of the evolution of the building and its architectural language, study the environment where the building and observe the unique architectural elements, we must ensure that all transactions will be made in accordance with the logic of the building design and original materials and avoid pastiche, seek the advice of professional expertise in the subject, we must put in mind that restoration is not the alteration or change.

　　Key words: Why restoration;Cleaning;Foundation

　　Introduction:

　　The restoration of buildings can refer to the act or process of accurately revealing, recovering or representing the state of a historic building as it appeared at a particular period in its history, while protecting its initial value. The work is often done to reverse the rot, or changes to the building after its initial construction. Part of the heritage restoration may involve the replacement of outdated heating and cooling systems with new, or the installation of air conditioning controls that never existed at the time of construction.

　　Restore an exterior masonry element if an evaluation of its general condition demonstrates the need to undertake further work as the work of preservation, if repairs on the masonry elements of the period demands.

　　Definition:

　　This is a direct intervention on a building in order to maintain his material integrity and ensure the conservation and protection of his culture values.

　　It regard reparation, renew, and substitution of the building and all the necessary work to integrate and maintain the efficiency of the technology.

　　Cleaning techniques:

　　The choice of cleaning method depends essentially on the nature of the facade to treat, diseases encountered, and degree of fouling, hence the importance of diagnosis. It will take account of different materials: concrete, plaster, stone, brick, glass paste, metal, wood ... and recognize the nature and maintenance of the existing coating on these different media.

　　The cleaning techniques can roughly be pided into three categories: mechanical cleaning, chemical cleaning and cleaning water. Cleaning water is the easiest method. This module is based on the amount of water, temperature and pressure of water. Mechanical cleaning primarily uses the techniques of projection. It requires a scaffold and special tools and generates as much dust as muddy water. Chemical cleaning is usually in the installation of ladders and the use of rinse water. It doesn’t use specialized tools or scaffolding, it is often cheaper. But this unfortunately cannot be applied to any media or any type of dirt present.

　　Cleaning water:

　　The simplest cleaning is done by spraying water on the surface until dirt is detached under the action of water and was evacuated with her. This technique has some disadvantages: the water con-sumption is high and the walls are soaked in water. This increases the risk of infiltration, promoting the development of algae, mosses, molds with all the damage they presuppose.

　　By moistening the surface without saturating it with water, it can be cleaned with a stiff brush(not metal). This is obviously a job that requires many hours of work and it’s therefore expensive. Not to mention that it will not come to the end of a stubborn or em-bedded soil.

　　You will get a better result by using projected under pressure saturated steam. To prevent that dirt stays, it is essential to use enough water to pull it up. The technique requires, of course, spe-cialized tools. Mainly applied to concrete, stone and other porous materials, it has been replaced in recent years, by cleaning with water under high pressure.

　　Cleaning water under high pressure detaches the dirt and wash in hot or cold water. To prevent damage to the facade, you must start by spraying at a good distance and adjust the pressure accord-ing to the material and its condition. This method is particularly effective on hard materials(bluestone, granite ...), but not on soft materials or altered by weather.

　　Methods of treating cracks:

　　Depending on the type of crack involved, treatment is not necessary in all situations. It depends on the characteristics of the crack. When cracks are sheltered and are not the result of a lack of reinforcements, it is not absolutely necessary to treat them.

　　The protection of the crack: When there is no structural risk, but it is necessary to protect the crack from infiltration because it is not sheltered from rain, streaming water ... there are 5 possible types of treatment:

　　Injection: it is about to inject into the crack a product capable of creating a mechanical connection and/or a waterproofness be-tween the separated parts to reconstitute the monolithism of the structure.

　　The caulking: it`s about to fill in deeply with flexible products to establish waterproofness and air tightness on the cracks, or to avoid penetration of solids to block the movement of the crack or joint.

　　Bridging and localized protection: to cover active cracks sur-face or not to provide a water proofness structure. It must allow if necessary the installation of a surface of definition.

　　The general treatment: This is a treatment which provides one or more of the following: aesthetic, additional waterproofing, water-proofness and waterproofing.

　　The superficial protection of the crack: in the case of a crack force that can act as an expansion joint, the goal is to cover(a metal rule for example fixed with oblong holes)and thus, protect it from water infiltration.

　　The frame:

　　Without changing the structure: the renovation is first to clean wood by scraping, sanding or sandblasting. Then a treatment with fungicide and insecticide of the wood will be done. Finally, the renovation ends with the installation of insulation and realisation of final work(wood stain, paints).

　　More seriously, from the outside: generally, it takes advantage of the renovation of the roof, after taking down the cover, for the so-livage review, to change irregular rafters or rafters in bad condition as well for the failures and defective beams and old wooden handle . In addition to the consolidation and protection against fungi and wood-eating insects, it facilitates the installation of effective insu-lation to lay a roof.

　　From the inside without touching the cover: it is perfectly pos-sible to review a frame made of industrial truss, to be replaced by a traditional structure to clear the area and carry out a habitable room, with of course following treatment, isolation and decoration.

　　The foundation (sole):

　　After a diagnosis of damage to the masonry, one must:

　　-Stabilize the soil by evacuating groundwater at the foundation by a drainage system that surrounds the building.

　　-Lighten if possible additional charges.

　　-Intervene in the basement, several systems interventions.

　　-Strengthen the existing foundation:

　　By injecting natural hydraulic lime in masonry foundation. The strength of the lime varies according to the volumes to achieve. By default, it will be a volume of lime to two volumes of fine and clean sand.

　　-Underpin the sole: After evaluation of the load transmitted to the ground by the foundation, we can define the suitable size of sole to provide stability to the wall. In the case of a good soil, just enlarge the soles to increase the surface charge distribution of the ground. This process consist in:

　　-Dig the ground on both sides of the wall down to the foundation.

　　-Digging below the existing sole on the half of its width. Proceed by steps of length not exceeding two meters each.

　　-Pouring reinforced concrete soles which dimensions and reinforcement depends on the load it will bear.

　　-Keep steel waiting for the continuity of the reinforcement in the new sole on the side.

　　-Dig on the opposite side of the first intervention, on the same height and the same lengths and widths.

　　-Clean steels waiting; complete the steel framework and the second part of the sole.

　　-Keep on the same principle the expansion of the sole.

　　Transmitted by micro-piles loads to good ground:

　　This technique is used in the case of fragile soil. It is to implant micro-piles that go down deep into the ground right below the existing soles. This solution needs to make prior borings to recognize the substratum and the level of good soil. Thus, it requires specific technics and specialized manpower in this type of work to avoid unforeseen problems. The micro-piles are piles of small diameter(15 to 20 cm), drilled by rotation to avoid any shock or vibration below the existing soles. These piles are armed with tight reinforcement forming tight compact prestressed concrete to withstand heavy loads despite their small diameter. They will be integrated inside the masonry of the foundation to ensure a perfect connection.

　　Paint:

　　-Cleaning, with sponges, brushes, strippers, of detergents, high pressure sprayers(eg Karcher)and gluers to die wallpaper.

　　-Work preparation or dressing, which involve backfilling operations, plastering and sanding to make the surface flat and flawless, ready to receive coating. To undertake this work, the artist uses tools(spatulas, knives, squeegees)and machinery(eg electric sander).

　　-The finishing works themselves, which are to realize the coating(painting, carpeting, wallpaper, etc. ...), with brushes, rollers, spray guns tires, glue, etc...

　　Requirements concerning drainage devices in buildings:

　　Depending on the slope, each building is totally or partially surrounded by drainage.

　　The drainage device is located along the foundations of the building, is situated at a distance of approximately 2 m from the exterior walls.

　　If the drainage is located immediately along the foundations, it is forbidden to descend trench drain to a level below of the foundations level. The drain hose is then placed on a concrete giving slopes implemented along the insole or on the border of the insole in relation to basement wall.

　　If the drainage is realized at a certain distance from the exterior walls it`s necessary to keep the streaming water far from the front and to bring it back to the drain.

　　This can be achieved with a counter-slope or with a super-ficial protection, etc... It is obvious, however, that in case of very large streaming of water on the front, counter-slope without super-ficial protection may be insufficient if the filling between the walls and excavation devices is done using permeable material.

　　If the building is based on a clay ground, it seems reasonable that the slope between the interior foundations leveling and the bottom of the trench does not exceed 1 to 3.

　　In the case of fine sand, the risk of decompression by entrain-ment of fines, under a water gradient even small and with important distances, leads to check the slope in which the foundations are views from drain water, not only for sole nearby, but for others as well. It is prudent in this case, not to exceed a slope of 15 %.

　　Conclusion:

　　Restoring an old building requires a certain knowledge to do so should contact the specialists in the field(architect or contractor)to diagnose, identify and assess the damage to determine the techniques to be used reliably restoration, especially the foundation which is the sensitive part of the building must be properly diagnosed before restoration for a good result.

　　For inpiduals who include in their project of life, restore an old house is like an adventure. As communities, they now support the transmission of their heritage, complete restoration of a building whatever; in accordance with the spirit of the place for all is a challenge.

　　So I call on everyone to respect the logic of restoration for a better result.

　　Reference

　　Patrimoine bati protégéau titre des monuments historiques et possibilitéd’intervention de la Fondation du patrimoine.

　　Label BIP de la Fondation du patrimoine maritime et fluvial .

　　CRATerre 2006.

　　Cours de restauration(University of Tianjin 2009)

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