Grand Housing Development Program Volume III - Gtz

CONSTRUCTION GUIDELINE STEP BY STEP(CONTINUED)Grade beams with ground floor concrete, expansion joints and columns up to first floorSanitary installationThe sanitary installation (waste water line) has to beinstalled at this time. If the waste water line goes belowthe grade beam the pipes should be installed beforethe lean concrete is in situ.The same procedure as with the backfill of the footingsshould be followed.Hardcore & Lean ConcreteThe best solution is that the waste water pipes crossthe grade beam in the middle. In the formwork for thegrade beam an opening has to be prepared so thatthe waste water pipes can pass through. The openingsmust be bigger than the pipes in order to avoid anycontact with the grade beam e.g. when the waste waterpipe has a diameter of 110 mm the opening shouldhave a diameter of 160 mm.As the waste water line has a slope of 2%, the openingin the grade beam should follow this slope.The hardcore consists of broken basaltic stones. Thestructural or resident engineer can change the specificationto trachidic stones.The hardcore has to be levelled so that it’s height isequal on all parts.On top of the hardcore lean concrete (C 5) has to beplaced and levelled. The lean concrete avoids that theconcrete on top (C 25) enters into the spaces betweenthe hardcore.Backfill between Grade BeamsAfter the deinstallation of the formwork for the gradebeams the backfill of the areas in between the gradebeams can start.It is very important that the lean concrete is levelled inorder to get later on the right distance (equal distance)in between the spacers and the temperature reinforcement.26Addis AbabaCity Government