Updated March 8th, 2019
RCC false slab is a slab which we make below or above the main floor slab.
There are various purposes of making false slabs. Some false slabs are made for the interior purpose. Some are made for hiding air conditioning ducts. Some are made for hiding any unwanted things.
I’m talking about the false slab which we make in bathrooms for hiding the sanitary pipes, traps, fittings, etc.
You can use various types of materials for making false slabs. But we often make RCC (reinforced cement concrete) false slab in bathrooms.
The advantage of making RCC false slab is, you can repair the sanitary pipes sitting on the false slab. Another advantage is if there is any leakage in the joint of sanitary fittings, the false slab will prevent the water directly falling in the bathroom. There are some other advantages of RCC false slab in bathrooms. Such as, dwellers can use this for keeping various household things.
To make the RCC false slab usable you need to check several things before casting the slab.
9 Things to Check in RCC False Slab Before Casting
There are many things need to be checked before casting RCC false slabs. I’ll describe them below. Once you check those things, it’ll save you from many unwanted hazards later.
1. Check The Clear Distance Between The Floor and The Ceiling of False Slab
We normally keep seven feet of distance between the bathroom floor and the false ceiling. This is the clear height of the bathroom.
If the clear height is less than 7′, it’ll make problems in many ways.
For example, we fix the shower at 6′-6″ from the bathroom’s floor. If the clear height of the bathroom is less, you need to fix the shower far less which make the shower unusable or decrease the comfort of using the shower.
Another thing, if the clear height is less, you have to reduce the door height of the bathroom. If the door height is reduced, that’ll make users uncomfortable to enter the bathroom through the door opening.
So, how do you maintain the clear height of bathrooms?
As I discussed above, the clear height of the inside of a bathroom should be 7′. So, you need to make the false at 7′-2″ above the floor. Because when we install tiles on the bathroom floor, it’ll be raised 2″.
So, check the clear height of bathrooms before casting RCC false slab in it.
2. Check All The False Slab And Lintel Level are Same On a Floor
The level of all lintel and false slab on a floor should be the same.
Imagine, you have two doors side by side. If the top of both doors is in different levels that will look ugly.
For this purpose, we fix a level on the floor. We normally take the level from the front of the lift lobby or stair lobby.
Mark the level on a column in the lobby area. Take that level to all flats in that floor.
Before casting any false slab, check the level of the slab in reference to the level you fixed in the column of the lobby area.
You have to do this before casting false slabs. it’ll make sure all the lintels and false slabs are at the same level on the floor.
3. Check If The False Slab is Truly Horizontal
The false slab of a bathroom should be truly horizontal. Because if one side of the false slab is up and another side is down, you’ll face problem during wall tiling work of the bathroom.
For making the false slab truly horizontal, mark the level in the all four walls of the bathroom with the help of a water level pipe.
Now check the distance between the level mark and the bottom of the false slab in all four sides. If the distances are the same in all sides, then the false slab is truly horizontal.
4. Check If a Drainage Pipe is Kept in The False Slab
As you know there are various drainage and water supply pipes run above the false slab. If there is any leakage in those pipes, there is a possibility to fall water on the false slab. besides this, water can fall on the false slab at the time of repairing drainage and water supply pipes.
If there is no drainage system to remove the water from the false slab, the water will come out to the room. So, we need to keep a drainage pipe in the false slab to take the water to the floor trap of the bathroom.
Before casting the false slab, make sure the pipe is kept in the false slab.
5. Check If There is Enough Room for Installing The Sanitary Drainage Pipes
We normally use 4″∅ pipes for floor trap and commode. The pipes from the upper floor bathroom run above the false slab. These pipes are connected to the building’s main sanitary stacks.
This problem is, if there is any beam above false slab in the way of sanitary pipes then it’ll be difficult to connect the pipes with stacks.
So, before casting false slab, make sure you won’t have any difficulties to connect sanitary pipes with stacks.
6. Check If You Kept The Cat Door Opening in The False Slab
The cat door is an opening kept in the wall to access to the false slab. The main purpose of keeping a cat door is to access the false slab to repair sanitary connections above the false slab.
It is normally kept in the wall above the false slab. But sometimes it is not possible to keep the cat door in the wall. In that case, you need to keep the door in the false slab itself.
Before casting false slab, check that you’ve kept a cat door in the false slab.
7. Check If The Reinforcement Work is Done Properly
As we do before casting any RCC member, so you also need to check the reinforcement of the false slab.
Make sure the size and number of bars are placed as structural design.
Make sure sufficient cover blocks are placed and concrete clear cover for reinforcing bar is maintained properly.
8. Check The Shuttering of The False Slab
Check the shutter of the false slab. If there is any leakage in the formwork of the false slab, rectify them. Otherwise, it’ll form honeycomb on the concrete surface.
Check all the supporting of the formwork are tightened properly. So that after placing concrete, the false slab doesn’t come down.
9. Check If The False Slab is Aligned With The Wall
This is another big issue I often face after removing shutter of false slabs. That is, the false slab comes out of the masonry wall.
If this happens, you’ll need to demolish the exposed concrete during plastering the masonry wall.
So, check if the false slab is aligned with the masonry wall.
Sum It Up
Checking false slab isn’t a big thing. You just need to keep some points in mind. Those points are – the clear height of the bathroom, the level of all false slabs and lintels in the floor, alignment of the false slab both horizontally and vertically, cat door position, enough room for assembling sanitary pipes, reinforcement, and formwork.
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