How to build a concrete ceiling

Mr. HowToSpecialist December 16, 2011 Comments Off
How to build a concrete ceiling

This article is about how to build a concrete ceiling. Pouring a concrete ceiling is not a common technique in United States, but is used on a large scale in Europe. Nevertheless, although it is more expensive and it takes longer as compared to a wood stud ceiling, it still has a few advantages which could make you think again when building your house. Consequently, when building a concrete ceiling the rigidity of your house will be much better and it could support more weight, as compared to light constructions. On the other hand, a concrete ceiling is so strong and durable, that you won’t hear any footsteps when sitting on the ground floor.


Building a concrete ceiling will increase the phonic insulation and durability of your house. But these advantages come together with a few drawbacks, such as the higher cost of the project or the fact that pouring a concrete ceiling may take up to several months, until you can actually build the walls and the roof. In addition, you have to build a formwork to be able to build the concrete ceiling.

Pouring a concrete ceiling is difficult without the help of a qualified engineer. In addition, you have to observe your local codes in order to get the construction permits. The thickness of the concrete ceilings varies according to the weight it has to support, but it is usually between 5-6” for residential constructions. Taking into consideration the weight of the rebar structure, as well as the weight of the concrete, building a sturdy form is essential for any project. Therefore, use thick wooden boards or panels to build the form and support the whole structure with 4×4 posts.

 

In order to build a concrete ceiling, you need the following:

Materials:

  • 1×4 wood boards for building the formworks / tego plywood boards
  • 4×4 wood posts to support the ceiling / adjustable metal posts
  • nails/wood screws to fasten the formwork

Tools:

  • safety gloves, glasses
  • measuring tape, carpentry pencil, l-square
  • circular saw/jigsaw to build the formwork
  • hammer

Tips:

  • use boots, as not to get your cloths and skin dirty with concrete
  • clean thoroughly your tools after you have finished the project
  • wear protective glasses and gloves, to avoid possible injuries
  • make sure the ceiling formwork is perfectly level

Time

  • few hours up to a day, according to the surface of your foundation and the number of workers

 

Building a formwork for the concrete ceiling

Building ceiling formwork

Building ceiling formwork

In order to build the concrete ceiling, one has to make a proper formwork. Building the formwork is a complex process, but anyone can do a job in a professional manner, provided it has some experience in working with lumber.

The complete details of the formwork, as well as of the reinforcing structure, have to be provided in the plans of your house. Remember that building a concrete ceiling is essential for the durability of your house, so you have to consult a qualified professional before starting such a project. In addition, you have to observe your local codes and get all the needed construction permits, as your safety is at stake.

Smart tip: when building the formwork, you have to use pressure-treated lumber, as to make sure it will support the weight of the reinforcing bars, as well as the concrete.

 

Formwork for concrete

Formwork for concrete

As you can see in these images, you have to build first the frame of the formwork, by using 4×4 lumber. On this structure you should install 2×4 wooden boards or tego plywood boards. The first option is better for the ones with a tight budget, but we recommend you to use tego plywood boards as the bottom of the ceiling will be perfectly straight, and you won’t have to put extra-effort to make it level.

If you are using wooden boards, you have to make sure they are straight and in a good condition. In addition, make sure you don’t leave gaps between the wooden boards, as the concrete might leak.

 

Smart tip: when building the formwork, you have to use a level, as to make sure it is perfectly horizontal, otherwise you will waste money and time to repair these flaws.

Building ceiling concrete formwork

Building ceiling concrete formwork

You can see the ceiling form from inside of the house, as to get a better grasp of the procedure. It might look unusual for the vast majority of you, but this is the proper way of pouring a concrete ceiling. You should notice that there are many 4×4 posts installed every 15”, in both directions, as to support the weight of the reinforcing structure and of the concrete.

Smart tip: rent adjustable metal posts when building your concrete ceiling. They support more weight and adjust to the height of your rooms.

Ceiling formwork structure

Ceiling formwork structure

We have drawn this sketch, as to show you in detail, how it should look the structure of the ceiling formwork. As we have already said, these details will be provided by the architects, but we want to get you accustomed  to these construction techniques.

Smart tip: use a 4′ spirit level to make sure the form is level and the support posts are plumb. Building a concrete ceiling requires, in most of the cases to build strong reinforcing structures, otherwise it won’t be stable and the walls won’t support its weight.

Ceiling formwork joint

Ceiling formwork joint

If you are using 4×4 posts, you have to thoroughly fasten them to the structure of your ceiling. Consequently you should use a 2×4 lumber and a few nails to lock them firmly. Use a level to make sure the 4×4 posts are plumb.

Smart tip: if you can afford you could use a table system, which is much better as compared to a wooden form. In addition, it is easier to make it level.

 

Building reinforcing structure for the concrete ceiling

Concrete ceiling rebar structure

Concrete ceiling rebar structure

After you have built the formwork for pouring the concrete ceiling, you have to build and lock into position the reinforcing structure. As the concrete ceiling is almost floating, being supported only by several walls and pillars, you have to use a lot of rebars (the architect will compute the needed amount of rebars)

Smart tip: if your formwork is made of wooden boards, it would be a good idea to install polyethylene foil over the whole surface, as to prevent the concrete from leaking.

Rebar structure

Rebar structure

In this image you can see a close-up with the reinforcing structure of the concrete ceiling. You might have noticed the rebar beams and you might ask yourself about their purpose. The rebar beams are placed on top of the walls and are connected with the rest of the reinforcing structure of the concrete ceiling. In this way, the concrete ceiling will be supported by the walls and will be more rigid and durable.

Smart tip: you should always follow the structural plans, otherwise you put your safety at risk.

Building concrete floor reinforcing structure

Building concrete floor reinforcing structure

In this image you can see the reinforcing structure around the stairways. You could notice that we have used many rebars around the stairs and alongside walls.

Smart tip: these kind of projects should be performed by trained and experienced professionals, so you should see our guidelines as for informational purposes. We recommend you to hire an experienced architect, which will suggest you a team of trained workers.

 

How to pour a concrete ceiling

Pouring concrete with hose

Pouring concrete with hose

After you have installed the formwork and the reinforcing structure, you have to pour concrete, as to finish the ceiling. Consequently, you should rent a concrete pomp and several hoses, to pour the concrete in the ceiling formwork.

In addition, you should order the needed amount of concrete from your local concrete company (they will deliver it with trucks). You should know that there are more types of concrete, so make sure you order the one which is indicated in your structural plans (usually for ceilings you have to use B 250). Ideally, you should hire an engineer to supervise the workers while they pour the concrete ceiling.

Smart tip: when puring concrete on a large surface, it is better to start with the the furthest corner. In this way you won’t dirty the hoses with concrete. In addition, you should wear rubber boots as to protect your legs from getting dirty with concrete.

How to finish concrete slab

How to finish concrete

After you have poured concrete in the formwork, you have to finish it with a bull float from one end to the other. But first you should vibrate the concrete, as to make sure there are no pockets of air left in the concrete ceiling.

After you have used the concrete vibrator, you should finish the concrete surface with a bull float. Make sure you finish the surface properly, making sure it is perfectly level. Nevertheless, in most of the cases you will have to pour screed after the concrete ceiling has dried out to make it perfectly level.

Pouring concrete flooring

Pouring concrete flooring

Next, you have to wait a couple of months until the concrete ceiling has dried out completely. After the ceiling has dried, you can remove the formwork and continue building the walls and the rest of your house.

 

Smart tip: if the outside temperature is high, you have to sprinkle water over the concrete ceiling at least two times a day.

Pouring concrete flooring

Pouring concrete flooring

Make sure you sprinkle water over the concrete ceiling, otherwise the ceiling will crack. In the worst case, you might even redo the concrete ceiling, if the cracks are too deep (the cracks might affect the rigidity of the ceiling).

 

Smart tip: do not remove the wooden form too soon, otherwise the ceiling will crack or it will become crooked. That is why, it is important to consult with a qualified structural engineer.

Constructing concrete ceiling

Constructing concrete ceiling

After the ceiling has dried out properly, you can start building the walls and the roof of your house. Pouring a concrete ceiling is not very difficult if you follow the guidelines from your structural plans.

 

Smart tip: just make sure you install the reinforcing structure properly, as to build a durable brick house. Make sure you use the right tools and materials, as to get the project done in a professional manner.

 

Thank you for reading our article on how to build a concrete ceiling, and we recommend you to check out the rest of our projects. Please share our projects with your friends, by using the social media widgets.

 Related projects:

 How to dig a foundation

 How to build formwork 

Comments are closed.