If you are building a house with builder/contractor supplying both the building material and labour, keep the following essential points in mind for avoiding any dispute later and peace of mind during construction. These are just a small set of points for getting a good house structure built.
1. Suppose your plot area is 1000 sq ft and you want to have a stamped agreement with a builder for constructing a double storey house on this plot. Sly builders often quote a lower built-up area (generally, built up area is the roof area and is measured for final construction cost). Once the construction reaches the first floor, the builder will say that the built-up area will exceed the built-up area of the deal if you want to construct second floor according to your plan. For the extra build-up area construction, he will demand extra. To prevent this situation, in the beginning itself when you are making the agreement, make sure that you deal with the builder to build a house with built-up area equal to your plot area (2000 sq ft in this example) plus stair-cover/mumty. Another thing is to insist on getting a full plan of the house before the construction begins that has build-up area equal to the area that you have mutually agreed upon. Do not give him any advance money until that plan is with you. Then insist on construction according to that plan. If builder says that plans may change during the construction, he may have that hidden agenda. Tell him the structure plan will not change.
2. Never sign an agreement where the column reinforcement bar size is lower than 12mm. Ring bars may be smaller, but no less than 8mm, and should be ribbed.
3. Note also to use concrete grade M20 (1-2-4 ratio of cement-sand-aggregate) or higher such as M25 (1-1-2) for beams and slabs.
[ NOTE: During construction you need to observe that the labourers/workers are following the grade mix. For some reason, they tend to use less aggregate and more sand than the recommended grade ratio.]
4. Use sufficient columns in design. Generally, for every corner and room joints in the house rooms there should be a column. If the room size is large, 18 foot or more, insist on a column in the middle.
5. In a house, generally there are 4 types of beams:
i. plinth beam whose upper end is at the floor level (unless you do some brick-work on top of plinth beam and then do DPC on top; DPC then becomes the floor level).
ii. Lintel beam (sometimes also called door band) that is smaller beam that runs just above the doors and windows (normally at 7 ft above floor level)
iii. Drop beam (also called roof beam, wall beam or latak beam) is put along with the roof slab and it hangs below the roof.
iv. Hidden beam (also called concealed beam, gutti or hajmi beam) is reinforcement that is as thick as the roof slab but is wider across the roof. It is often used by builders in place of drop beam for cost-cutting.
As a rule of thumb, in the agreement insist on plinth beam, DPC, lintel beam at every floor, and drop beams at every slab.