Water is the biggest friend during construction, but during maintenance of the building water can be the biggest enemy as it corrodes the Steel extremely fast and makes the building structure weak.
It is important to make sure that the Steel Bars inside the Reinforced Cement Concrete (RCC) portions are tucked away from water and even air (as moisture is sufficient to corrode the steel). Our commonsense approach makes us think that Concrete is waterproof; which it is but not 100% and therefore water penetrates through Concrete if left stagnant for a little longer duration. Therefore it is important to coat the Concrete Surface with good quality waterproof materials. Waterproofing costs just 1% of the Building Construction cost but many construction people are technically not aware of how to use the right waterproofing materials which is a vast complex subject by itself.
Many a times, the tendency is to skip that 1% Waterproofing cost either because of the cost or because of ignorance.
What happens when Waterproofing is skipped?
Typical symptoms include wetness, discoloration below the bathroom either in the Ceiling or in the Adjacent walls - at this stage it is very early and probably not yet affected the steel corrosion, and might be the right time to set it right.
Quick Hack for setting it right:
Remove the old Grouting (which would typically be Cement based) in the Bathroom Tile Joints and Replace them with Epoxy based Grouting (Laticrete SP-100 is a good example). This is a little expensive but will not allow further water to enter through the tile joints.
But this Hack is not enough if water has already entered through the tile joints and is now staying inside the Sunken Slab because that water is going to enter the concrete sooner or later. It is very difficult to diagnose this and is a judgemental call which comes out of experience.
To Solve this problem permanently, waterproof the Bathroom floor:
Remove the Commode and Gratings and keep them safely.
Remove the old Floor Tiles completely, typically this involves breaking them and disposing of the broken tiles.
Remove the existing Sunken Slab filling completely and wipe it. Typically it could be some soil, brickbats or in some cases debris.
The Plumbing lines also need to be removed if they are lying on the sunken slab floor; but if they are floating above the floor even by a couple of inches they need not be removed.
If Concrete surface is seen, then obviously there was no plastering done and therefore no waterproofing done previously.
Now plaster the surface smoothly. If the Concrete surface is seen to be damaged then a fibermesh can be placed and then plastered - which acts like reinforcement for the plastering.
Complete the plumbing with a 1-2” gap above the plastered surface so that waterproofing can be done in the next step. If this is not possible then make sure that the plumber jointly works with the waterproof guy to coat the bottom surface and simultaneously keep the plumbing pipes.
Waterproof coating of the smooth surface using a good waterproofing chemical (unavoidable) like Fosroc Brushbond. This needs to be applied at least 2 times - once in the X direction and once in the Y direction. This is a costly chemical and would typically cost about Rs.40-50 per Sq.ft. of application. Sometimes a third coat in the X direction again can be done if there is suspicion of damaged concrete surface or if cost is not a big constraint. There are slightly superior chemicals like Brushbond RfX which are even better but costlier.
And also pack the plumbing exit points, plaster it neatly and waterproof them too.
Keep a weep hole (typically a ¾” pipe) on the plastered surface lowest point projecting out of the building. (This will be an alarm bell if it leaks again later when the grouting is gone and needs to be replaced, but this time it won't be a worry because waterproofing would be done.)
Allow the waterproofing coat to dry up completely.
Seal the outside of the weep hole temporarily from outside and allow water to stand for the full depth of the sunken slab up to the floor level for at least 48 hours. This is a critical test of waterproofing. If there is a leak it will be visible below the slab. If so, additional coats of waterproofing are to be done or in some portion the coating was not done properly.
If the water test is passed, allow the water to drain completely out of the weep hole ONLY - this is the test for the weep hole functioning.
After that make sure once again that the plumbing lines are completed without any further breakage or damage to the waterproof coating.
Fill it back with soil (best approach). Avoid debris as they can puncture the waterproof layer. If using Brickbats, the waterproof layer needs to be plastered again before pouring brickbats as they will tend to pierce the waterproof layer while being manually compacted.
Retile the Floor and any damaged portions of the wall
This time use Epoxy Grouting for filling the joints
Fix back the Commode and the Gratings.
Approx Cost & Duration Breakup
Let us look at the cost impact:
# | Work-Item | Qty | Unit | Rate | Amount | Duration (Days) |
1 | Removing Bathroom Fittings | 0.5 | Man Day | 1200 | 600 | 0.5 |
2 | Breaking Existing Tiles | 1 | Man Day | 1000 | 1,000 | 1 |
3 | Removing existing Filling | 2 | Man Days | 1000 | 2,000 | 1 |
4 | Plastering Surface (with Fibermesh if required) | 75 | Sq.ft. | 55 | 4,125 | 1 |
5 | Waterproof Coating | 75 | Sq.ft. | 50 | 3,750 | 1 |
6 | Plumbing Lines & Accessories | 1 | Man Day | 1500 | 1,500 | 1 |
7 | Testing | 0 | 2 | |||
8 | Soil Refilling | 100 | Approx | 25 | 5,000 | 1 |
9 | Purchase of New Tiles | 75 | Sq.ft. | 50 | 3,750 | 0 |
10 | Tiling Labour & Cement etc | 75 | Sq.ft. | 50 | 3,750 | 1 |
11 | Epoxy Grouting | Approx | 2,500 | 1 | ||
12 | Fixing Bathroom Fittings | 1 | Man Days | 1200 | 1,200 | 1 |
Total | 29,175 | 11.5 |
Caution
While the above is the approx cost, it may be difficult to procure items at this cost while repairing just one bathroom. Additionally, shifting to the upper floors, transport costs are higher for smaller quantities. Therefore the cost may shoot up to Rs.50,000 per Bathroom and will need a minimum of 2 weeks for this work to be done by a very efficient plumber, mason, tiling team but can extend to about 3-4 weeks when different skilled people may not possibly collaborate or adjust their time accordingly. It is better to be prepared for the higher amount and duration.
What was earlier Rs.5000 has now become Rs.50,000! A Stitch in Time saves Nine Stitches - at least 9 times cost could have been saved by not skipping the initial waterproofing.
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