[RaSing]

My friend in Jodhpur has built a big home theatre(can seat 10-15) room, a maids room and some storage rooms in his plot. You can think about utilizing the basement same way in case you have a need.

[Amrik Singh]

The best part of Basement is a constant and cooler temperature. Can be used to store non-inflamable and dry items that do not require very low storage temperature.
As for water ingress, you have to slope entire floor towards drain pit with two (1duty + 1standby) submersible drain pumps.
Distribution board for Basement Electricals should be on ground floor to prevent it from getting submerged in water in rare case of flooding.
Suitable ventilation must be maintained.

[rhsakarp]

@nec2152, couple of friends in Bangalore have houses with basements. They have faced multiple issues over the years, like water ingress during heavy rains, cracks and seepages in the side walls, some weird smells etc. Would recommend leaving the stilt floor open for parking etc. and build higher, depending on your need

[Precision]

Originally Posted by nec2152

The construction has just begun

Please elaborate what stage the construction stands as of today. If you have already cast the footings and tie beams then you are going to have to demolish it and remove the debris from the site, then excavate further and start from scratch.

Please also talk to your architect w.r.t using the basement as a probable habitable place and also what effect it will have on the Floor area ratio.
If you are using the basement for anything other than parking then the F.A.R will take a negative hit.

15L is just about enough in my opinion to do a good Job for building out 1,300 Ft2 underground and it largely depends on your water table at site.

If you do go ahead and build it out then you will definitely be the envy of your gang and guaranteed party spot

[abtyagi]

I was watching a documentary sometime ago, apparently in London repurposing basement is quite common. People add pool, theatre, storage, and what not. There may be engineering difficulties but if executed well, looks really neat. Attaching a sample image. I am sure google will give lot more information.

[SandyX]

Get the basement done while you still can. Wrap before casting and it'll last for generations without seepage. Make sure provisions for ventilation & sanitation are implemented properly, so that it can be put into survival duty as well in case things above ground goes sideways.

I believe 10-12" casting is standard for the space you're aiming for. Make sure the access, ideally cast, is above the maximum recorded flood line in your area.

Even if it costs a pretty packet at present, it's a investment well worth its utility.

[sukhbirST]

Originally Posted by sagarpadaki

2. Flooding/water accumulation during heavy rains. Preventing water from entering the basement can be mitigated to a large extent by covering the entrance to the basement. However if the road floods then you cannot prevent water from entering the basement. Depends on the locality where you stay.

Agree with the flooding part, plus need to check seepage in the walls.

[Ricky_63]

Basements are usually built with RCC retaining walls. So newer constructions do not have the problem of seepage. I am building a Basement with a sunken court on the rear end, so I get natural light (like ground floor) in the basement.
I will be putting in an automatic sump pump there to pump out any excess rainwater.
In case of a stilt + 3 or 4 storey building the footings for the foundation take care of upto 70% - 80% concrete at the base of the building. I will be filling up the rest with concrete to ensure no water seepage from the ground.
All in all this is the tried & tested way to go, as basement is free of FAR in Gurgaon (don't know the building by-laws in Pune)
So in my books if I spend an additional 7-10 lacs and get 1700 sft of area, it's a no brainer. Ofcourse it all depends on the use of the same or lack thereof.

Hope this helps

[keroo1099]

Originally Posted by Ricky_63

In case of a stilt + 3 or 4 storey building the footings for the foundation take care of upto 70% - 80% concrete at the base of the building. I will be filling up the rest with concrete to ensure no water seepage from the ground.

I'm sorry, but this is just wrong info. Your foundation should be around 5' below the floor of the basement for a Stilt +3-4 structure. The floor of your basement isn't the foundation for your building so in essence the entire plinth within your RCC basement walls needs to be filled with PCC/concrete.

A good way to prevent/minimize ground water from entering the basement from the sides is to fill the excavated area outside the basement wall with sand, which helps in draining water down and away from the basement.

I wouldn't advice anyone to build a basement if the ground water table is high, or the soil around the house is has a high clay content. It's just not worth the risk in the long run.

[Ricky_63]

Originally Posted by keroo1099

I'm sorry, but this is just wrong info. Your foundation should be around 5' below the floor of the basement for a Stilt +3-4 structure. The floor of your basement isn't the foundation for your building so in essence the entire plinth within your RCC basement walls needs to be filled with PCC/concrete.

A good way to prevent/minimize ground water from entering the basement from the sides is to fill the excavated area outside the basement wall with sand, which helps in draining water down and away from the basement.

I wouldn't advice anyone to build a basement if the ground water table is high, or the soil around the house is has a high clay content. It's just not worth the risk in the long run.

Ofcourse the foundation for a building goes much lower than the basement floor.
What I was saying is that the concreting of almost 70 to 80% of the floor area already is concrete as the columns are set in concrete.
Apologies if I was unable to express myself correctly

[bkc]

Originally Posted by nec2152

Thoughts of what the usages and cons are for having a basement ?

Thanks !

I think, I'd be able to answer this better since, I'm in the field for 9yrs.

1) Firstly, you won't be able to do a proper UG for 15 lacs (for the 1300+ area you specified). Provided the current steel and cement prices, it is not possible.

2) Whether it is retaining wall or not, most of the cases the retaining wall is prone to water seepage, as the construction quality in smaller plots, is not so controlled.

3) Usually for UG, I plaster the exterior of outer retaining walls with smooth cement plaster and waterproof it. (Outside of the walls, just like water sump), later fill the soil.

4) Do not connect the UG drain to main drain of your street, it'll back flow, irrespective of using NR valves ( due to rodents).

5) For Ug, make a rainwater pit, connect the drain of UG to the pit. Make sure, street water doesn't enter Ug, from road, plan the ramp that way.

6) Place a auto Sewage pump in that rainwater pit and connect the pipe to the street rain drains. It will pump once the pit starts filling.

7) Make sure, your footings are deeper than the sump depth.

8) Never make any hole in the UG, below ground level.

9) Since you are making a UG, if possible try to support the compound wall with small pillars, maybe the neighbour won't dig so deep and your compound is very safe.

Thanks,
Bharath

[vinya_jag]

A few inputs from my side:
Pune being a 100+ cm/ year rainfall region, you need to consider twice before going for a basement.

What do you do before considering building a basement:
- Check the layout of the area. You cycle around the area for a few minutes to find out which if you are in a low lying area. Cycling gives you a very good indication of slope and that would indicate which way the water would flow.
- If you are unable to spot the gradient difference, use strava, that gives a good estimation of elevation gain. Walk in each direction from your plot and see the elevation gain.
- If your plot falls in the last 20% elevation amongst your surrounding roads, better stay away from the basement construction. Water will find its way towards your plot, from all possible directions.
- If there is a storm water drain close to you, the layout planners saw this coming, and built a storm water drain. Avoid basement construction at all costs, when this happens.
- Next is to watch the direction of water flow during a monsoon. Does water flow from left to right, or right to left, down your street. If it is from left to right, you would be better off building your basement parking on the right corner (You have more control over the water direction)
- Watch if your road tilts towards your plot or away from it. If it tits towards your plot (Even if your opposite house washes their car, the water would flow towards your plot). Avoid basement if this is the case. (Ours was this case, but we found a work around, of diverting water)
- If your plot doesn't have good drains in the front, again avoid basement altogether.

Assuming that your plot is at a higher elevation, and the direction of waterflow is away from your plot, next
Consider these while building the basement:
- Do you need a full basement (-6 or -8 from ground), or is it okay to build a (-2/ -3ft). Ours is a -2
- Did you consider building a Mezz floor for your parking? A simple 7ft height should suffice for car park.
- Every 1 feet you go under ground, you need 2+ ft of ramp to make it easy for taking the car out. So, if you are -4, you will need a 10 ft distance from the edge of the property before you park the car.
- Also, start by ramping up to your plot, before you start ramp down. This will avoid road water entering. Remember, water avoided is better than draining it from inside.
- Do you plan to have trees or garden area around your house within a few feet of the building? If yes, you will need bullet proofing to avoid water seapage.
- Your Man cave + parking is ideal (Thats what we have done, where I spent the last two years working from home).
- If you wish to leave the entire stilt for parking, you will end up paying the same price as your master bedroom, for an unused piece of land. You won't be using all of your car parking unless you have 4 cars, or 2 cars and a lot of two wheelers. (We park 2 cars, 2 two wheelers, 3 cycles, in half plot parking (1200/2 Squares)
- Ensure there are multiple levels of run off drains for the water to flow into the drain outside.

Other points:
- However good your planning is, it would take a couple of years of rain to understand and fix any problems.
- However low you go, the main living area will now be above ground and would take a few stairs to reach. Older folks will always complain when they come down to your house.
- Avoid wooden flooring at all costs. Our vinyl withstood the dampness, but not the wooden sideboards. They are up for replacement, just after 4 years. The prolonged monsoon last year let a lot of dampness seap in.
- If you have to build a bathroom on this floor, it needs more planning, and understanding of the drainage slope.

And finally, the positives
- Light, Light, More Light. Living area can never be at zero level these days, as it can get ultra dark, unless you have a courtyard like construction.
- You can stove away all the unwanted things in the basement, like the sump, gas cylinder, UPS house, rain water harvest tank etc.
- The Man cave, which everyone wishes to have. We originally built it as a home theater/ guest bedroom.
- Basement is the coolest place in Summers, and the warmest in winters.
- Extra storage and dump yard.
- Quiet

[BhayanaV]

For your use case, honestly it doesn't make sense to have a basement. I have lived in houses with basements and it's too much to maintain. Unless you have clear use or spare money & time to do something exciting, would not recommend it.

[Huzi]

Generally in metro cities, basements are constructed with the intent to create space for parking, but IMO:
1) if you don’t need parking space, there is an option to even rent it out.
2) sometimes i have noticed that water seeps into the basement even from the floor I.e ground up, if unattended, this weakens the foundation & later the structure, you will need to do preventive maintenance regularly to keep this in check.

If this is a dream home you are making, do consider your privacy, before sub-letting a part of it tenants.

[Livnletcarsliv]

Simple, ditch the basement (which is of no real use to you based on your points).

Use the same money to upgrade the wheels for more fun and happiness which is what I would do eyes closed