How to do a waffle slab: a step by step guide
In this guide, you are going to know exactly how to a waffle slab from start to finish
GENERAL CONSTRUCTION
How to do a waffle slab: a step-by-step guide
Waffle slabs are one of those types of slabs that seem complicated at first when you hear about them, but once you break it down, it's actually not complicated. If you are building a structure that needs a strong, lightweight, and long-spanning floor and roof system at a low cost, a waffle slab must be a perfect fit.
In this post, I'll walk you through a simple step-by-step guide to building a waffle slab from start to finish
Table of contents
1. What is a waffle slab?
2. Where are waffle slabs used?
3. Tools and material you'll need
4. Step-by-step process of doing a waffle slab
5. Curing and finishing the slab
6. Frequently asked questions
1. What is a waffle slab?
A waffle slab is the type of slab made of concrete structures called waffles. It has a grid-like pattern underneath created using moulds, which reduces the amount of concrete used when casting concrete for the slab while at the same time keeping it super strong.
2. Where are waffle slabs used?
Waffle slabs are best for
Large open areas with minimal internal support like malls, classrooms, parking areas, and auditoriums
High-end residential and commercial buildings
Places where aesthetics matter because they look nice from below
3. Tools youll need to do a waffle slab
Leveling tools, for example, a dumpy level or water level
Trowels
Tape measure
Vibrator for concrete compaction
Power tools for formwork
Trowels and spades
Materials required
Concrete
Steel reinforcement bars
BRC
Waffle slab molds are usually plastic or metallic
Props or scaffolding
Binding wire and water for curing
Step-by-step process for doing a waffle slab
STEP 1. Site preparing
Clear the construction area, and make sure the ground that is going to support the props is level and firm.
STEP 2: Set up formwork
Set up temporary supports or props to support the slab
NOTE: At this stage, when you have already precast waffles, you have to lay them properly on the prepared formwork
Or in case you are going to cast concrete directly, you need to place the moulds directly on the timber formwork, which can be removed later after the concrete has set. The most common one is bringing precast waffles
Step 3: Place waffles on top of the timber
This is where the shape comes in. Place your precast concrete waffles in a grid-like pattern. Make sure they are evenly spaced without leaving any gaps and securely placed
Step 4. Steel reinforcement
Fix and tie steel reinforcement bars over and around the waffles. This usually includes steel bars around columns and beams, steel bars between each waffle, and also a BRC steel reinforcement on top. Use a spacer block to ensure that the right concrete cover is maintained in the slab.
Tie everything with binding wire to keep it in place while pouring concrete.
Step 5: poring concrete
Pour concrete over the entire slab. Make sure the fresh concrete flows to all gaps between the precast concrete waffles and also covers all reinforcements
Use a concrete vibrator to to remove air bubbles from the concrete
5. Curing and setting of the slab
5. Curing and setting of the slab
Sprinkle water regularly on the slab at least 3 times a day for at least 14 days.
Once the slab has fully cured, you can remove the timber or waffle moulds, if you used molds, and then do the final finishing and painting on the slab
6. Frequently asked questions
Why is it called a waffle?
Because the underside looks like a waffle grid shape, with squares or depressions formed by already shaped moulds.
Are waffle slabs stronger than flat slabs?
Waffle slabs can handle longer spans and handle heavier loads without failure compared to flat slabs
Waffle slabs also have a good-looking finish at the underside or soffit, of the slab
What are the disadvantages of a waffle slab?
It's more time-consuming than other types of slabs
Needs skilled labour for proper setup.
Can waffle slabs be precast?
Yes, of course, some companies offer precast waffle panels which are made in a factory and then transported and placed on-site.
What is the size of the waffle panels
Big panels are 900mm x 900 mm, and then half-size is 450mm x 900 mm.