Jack Arch Roof
Jack arch Roof construction can be done in brick or concrete. The arch of the Jack arch roof is either made of brick or of concrete. The arch is supported on the lower flange of mild steel joists (RSJs). The rolled steel joists are supported at their ends on the walls or on the longitudinal girders. They are spaced at a distance of 1m to 1.5m centre to centre.
Jack arch Roof - Detailed Section
The rise of the arch is kept equal to 1/12th of the span. Layer of concrete is then poured over the roof to straighten the roof. The concrete layer thickness over the crown of the arch is not less than 15cm.
Due to the super-imposed load on the arch, tension develops at the ends of the arch. Steel tie rods are placed at the ends of an arch with a suitable spacing of 1.8m to 2.4m.
In this article, we are going to study the causes for leakages in a Jack Arch Roof and remedy to solve the problem of leakage.
The two main causes of Jack-arch roof leakage are:
- Poor quality of cement
- Inappropriate grade of sand
Repair of the roof
The Jack Arch roof leakage problem has to be fixed and should be so done so as to avoid future recurring water leakage problem. This can be achieved by waterproofing the roof.
Here are the four simple steps to repairing and waterproofing the Jack Arch Roof:
Step one:
The old cement mortar and tiles are to be removed so that the new cement mortar settles and becomes firm over the rough roof surface.
Step two:
After scraping of the cement mortar, fresh cement mortar is laid and left to dry.
Step three:
After the drying of cement mortar, waterproofing is done to avoid any kind of further leakage. Waterproofing material is mixed in a drum of water and splashed over the cement mortar layer. We must make sure that every corner of the roof is to be covered with this waterproofing material.
Step four:
After the process of waterproofing, tiling is done with the help of a suitable adhesive.
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#1 by Alan on July 29, 2010 - 6:26 am
Jack arch roofs are not only stronger, they also provide beautiful look to the building. One should take proper precaution while building this type of roof, and keep a correct proportions of cement, sand and water, otherwise, it will effect the durability of roof.
Alan,
#2 by BenzuJK on July 29, 2010 - 7:18 am
Correct Proportions of cement, sand and water applies for every type of roof. Jack arch roof was previously used to cover large spans and was commonly seen in Ancient Palaces. They don’t really make any difference to the exterior of the structure but could make a difference to the interiors.