ground water and foundation 1

[waseem19]

I’m looking for help on problem ,, we a have a small residential building to be constructed ,part of it below ground level ,,water level is high ,if you seal the bottom layer of the foundation what will prevent the water from rising up around the building ,, is de-watering for the building life an appropriate solution ? even if i manage to seal all the land ,,it's lower than the land next to it so water will flow from it to, and since the building is small in size water pressure can cause even worse problem than it would if i let it out ,, plz help

 

[Lutfi]

Waseem,

The presence of water is not a new problem to basements and structures. I recommend that you provide first and foremost a good and practical water tight membrane around the entire basement wall. This may include the use of tar type products, special keyed joints with proper water stops.

I would also place drains (perforated pipes) all around the building perimeter and convey the water away from the building.

Last but not least, you a good and experienced contractor to do the construction due to the special attention required for the joints and other construction.

I would use reinforced concrete walls with proper thickness to resist the earth pressure, water pressure and the axial loads from the building walls.

I hope this helps.

Lutfi

 

[edcmy]

You may also need to look into the instrumentation requirements to monitor the surrounding buildings and ground due to ground movements, which may be severe during excavation of basement and loss of ground water which cause ground subsidence. This is especially critical when the surrounding is founded on shallow footing or pad foundation, hope this help.

 

[ARIFSIDDIQUI]

a better option may be that u can provide a subfloor drainage system as the mass of the building is less than the water pressure than it is really a problem for the building u have to exploe a potential system for drainage below the building and this subfloor drainage system u can laid atleast .03 to 0.5m below the base of the building.the subfloor drainige includes of PCC Layer + geotextile membrane layer + again concrete layer but it is not mandotary u can use other materilas as well ment for this prupose

at last u should consider more on drainage system rather than design of the building because structural stability u can provide through calculation on paper but physicall stability can't be ensured through bookish calculation for such critical conditions.

 

[jheidt2543]

Another thought, how about RAISING the basement floor level. Yes, this could require a lot of fill around the house, but it may well solve the water problem for good, without pumping. Long term costs could be a lot less!

 

[epr]

Don't forget buoyancy! I have seen many basement floors cracked and heaved due to water pressure from below.

Obviously, the best means of preventing water in the basement is to elevate the floor level. However, if a basement floor must always be below ground water, and in the extreme case if it must be almost completely submerged in ground water, the basement walls and floor could even be structurally designed as a boat hull.

Also, for waterproofing purposes, once a basement is constructed there will be no way to access the waterproofing membrane for repair in case it leaks. Synthetic membranes can be damaged during construction and the leak created by same wuld be difficult, if not impossible to correct. Therefore I recommend good old-fashioned clay (installed on a working slab), which is self-healing upon contact with water. Volclay panels are a convenient means for providing a clay membrane.

Another good means of eliminating any water seepage (especially in a commercial finished basement where valuable items exist), is to provide a bathtub within the basement, comprised of a concrete slab on top of a drainage layer (either a 4" to 6" layer of washed stone with perforted pipe drainage lines, or (for lower ceiling heights) a dimpled panel such as Delta-MS Air-gap / drainage membrane by DORKEN)combined with the membrane against the inside face of the structural walls to direct any water seepage into a sump system.

 

[Focht3]

Raising the basement is only practical if the basement level is above the highest groundwater level that will be seen in the life of the structure. A properly designed subfloor and wall drain system - and excellent waterproofing - will probably be required. Perforated pipes alone, without a properly designed filter around it, will likely fail with disastrous consequences.

It will be expensive.

 

[Ron]

De-watering the subsurface of the building for life? Not practical for residential structure in high groundwater condition. Lutfi is correct...use appropriate waterproofing membrane design for the exterior of the wall.

 

[Focht3]

Permanent dewatering for residential structures is done where a basement is required, the permanent water table will be above the basement floor, and the owner wants to maintain a dry basement for the life of the structure.

Failure to provide a true "belt and suspenders" approach is just plain foolish when it comes to constructing a living space below the permanent water table. Too much has to be perfect in order for the waterproofing to work without leaking fo 30+ years.