Home knit baby thingsDo flat roof renovation yourself Cost of a flat roof waterproofing

Do flat roof renovation yourself Cost of a flat roof waterproofing

Flat roofs are among the roof types that need to be renovated most frequently. This type of roof is completely watertight, but the maintenance effort is significantly higher. If the renovation is disregarded, severe damage can occur within a short period of time, causing high costs. For this reason, many are wondering what the costs of a self-made flat roof seal are.

The cost of a flat roof waterproofing for professionals is not exactly low. Depending on the effort, these can be in the four-digit range. Especially if the flat roof has not been serviced for a long time, you have to expect to have to dig deeper into your pocket. In order to keep costs low, more and more people are switching to flat roof renovation on their own.


  • Do flat roof renovation yourself
    • Cost of a flat roof waterproofing
  • Do flat roof renovation yourself with 3 methods
    • Instructions | Liquid plastic
    • Instructions | Bituminous membrane waterproofing
    • Instructions | EPDM rubber Roofing

Do flat roof renovation yourself

However, implementing a flat roof renovation yourself is an extensive project that must be well planned. The materials used for sealing are particularly important for this. Without this, it is not possible to seal the flat roof again without having to hire a professional.

Cost of a flat roof waterproofing

Flat roof renovation is one of the cost items that, depending on the condition of the roof, can cut deep into your own assets. A complete renovation of the flat roof is only necessary if there is major damage. Here the costs can be in the range of several thousand euros, especially for larger roofs. However, if it is only a matter of refreshing the renovation tracks, the final price for the renovation will be drastically reduced.

roof shapes

The use of professional renovation railways costs according to experience points as follows:

  • 20 to 50 euros per square meter
  • Hourly wages for roofers
  • possible controls

In a garage with a size of 10 m², you would have to spend at least 200 to 500 euros just to renew the renovation lanes. Hourly wages are not included in this price. This still very low cost is only possible if none of the following shortcomings prevail.

flat roof
  • Thermal insulation material damaged or no longer effective
  • water damage
  • Attic needs to be raised
  • Drainage system out of date

thermal insulation

It is these positions that drive up the price of roof renovation. Thermal insulation alone can cost between 90 and 150 euros per square meter, depending on the desired thickness of the insulation material . Raising the parapet can be just as expensive if necessary.

Insulating material

Tip: In many cases, renovations to the house can be financed through a small loan. These are not to be confused with short-term loans, since they often have to be repaid in one fell swoop and interest beyond the interest rate for the overdraft facility can be incurred. Always pay attention to the conditions - even with short terms and sums.


These positions are usually not required for a pure renovation of the waterproofing. If such damage is discovered after the roofer has checked it, you should not carry out the renovation yourself. Otherwise, it is not a problem and you can save a lot of money because the roofer does not have to pay hourly wages. The purchase or rental price for the tools is usually significantly lower.

Tip: If you want to avoid high costs due to the flat roof renovation, you should have this checked at regular intervals. One check a year is particularly effective in identifying possible defects that you can correct yourself.

Do flat roof renovation yourself with 3 methods

If the cost of a new flat roof waterproofing is too high for you, you can tackle it on your own. For the handyman, there are numerous ways to securely seal your own flat roof without having to spend a lot of money. In addition to the appropriate tools and utensils, certain materials are required for these that are suitable for sealing at all.

You can use the following methods for this project:

  • Liquid plastics
  • bitumen sheets
  • EPDM rubber

Each of these methods leads to the desired result in the end, only they are applied and prepared completely differently. They are also suitable for private use and no heavy equipment is required that requires the use of a professional. Good planning and sufficient time are important, since the sealing can be very complex depending on the size of the roof.

With the instructions below you will effectively seal the flat roof of your garage or other objects. But don't forget to implement the following methods only with fall protection . Even with a low flat roof, accidents can quickly occur if there is no fall protection.

Protection by straps

This can consist of:

  • ropes
  • bars
  • fences

Colored tape is sufficient in most cases to prevent problems. If you cannot place a fall protection device on the roof, use one of the numerous belt systems that can actually be attached anywhere. In this way you protect yourself in an absolute emergency. For each of the methods mentioned, other tools and materials are required, which are presented in the respective instructions.

Instructions | Liquid plastic

One of the simplest and cheapest methods is to use a liquid plastic based on various materials. The advantage of using liquid plastic is that you don't even need certain devices to renovate the flat roof. These are most often used for waterproofing balconies, but they are equally effective for flat roofs of all sizes. They have many advantages that are particularly available for the homeowner.

  • low cost
  • effectively fills cracks and gaps
  • does not affect the statics due to its low weight
  • easy to apply
  • low layer heights
  • resistant to mechanical, chemical and natural influences
  • no flooring is required
  • available in colors
  • can be used together with anti-slip flooring
  • Damages are immediately visible
  • short drying times
Bitumen roof protective coating

The only disadvantage of this variant is the need to laboriously remove all of the plastic if a completely different covering has to be used. The effectiveness of the adhesive can also be very poor if inferior products are used. When choosing the liquid plastic, you should therefore use a product from a manufacturer that is known for its quality. Are recommended.

  • Caparol
  • triflex
  • AXOL
  • Alsan


The average price of a kilogram of liquid plastic for sealing flat roofs is between ten and 15 euros. Two kilograms are required per square meter. As you can already see, this variant is significantly cheaper than professional use. In addition, many manufacturers offer a volume discount if more buckets are ordered. If you want to make the flat roof accessible, you must also use bedding. The plastic is quite smooth and the surface makes the surface rougher and accessible.

Suitable interferences are:

  • quartz sand
  • grit
  • ceramic products

These provide the necessary finishing touches that make the flat roof usable. If you decide to use the liquid plastics, you must observe the manufacturer's instructions with regard to the following properties.

  • Working temperature
  • Drying time to walk on and in relation to precipitation
  • necessary equipment to use the plastic
  • Resistance, for example against UV radiation

Weather conditions

This not only makes your work easier, the result is impressive. You should never try to apply the liquid plastic, for example, in rainy weather, in winter or in the blazing sun and extreme heat. This usually leads to a variety of problems that could negatively impact the bottom line. The following utensils, with which the project is realized, are also important for the implementation of the flat roof renovation.

  • paintbrush
  • paint roller
  • Painters Plane
  • sealing tape
  • optional: straightening staff
  • optional: bedding material
Note weather conditions

No more is needed for this project. The plastic is applied wet on wet, which enables a consistently dense surface. You can carry out the renovation yourself with the following instructions .

Step 1: Start by removing the previous covering on the flat roof and preparing the surface. This should be smooth and clean. If the covering is only slightly brittle or cracked and still looks good in itself, you do not need to use this step. The layer thickness of the liquid plastic is so small that several layers do not really attract attention.

Step 2: Now edges and individual objects are divided with the sealing tapes. This allows you to coat the entire surface with the liquid plastic undisturbed. This is particularly important for flat roofs with solar cells or solid flower pots so that they do not come into contact with the plastic.

Flat roof with solar cells

Step 3: Now it's time to apply the liquid plastic. This no longer has to be mixed and can be used directly from the bucket. It is advisable to stir the plastic a little beforehand so that it becomes a homogeneous mass that is easy to apply.

Dip the paint roller into the plastic and apply it like paint on the flat roof. Be very careful to repair any cracks and bumps . Feel free to brush over part of the surface again and again because the plastic works best wet on wet.

Bitumen emulsion

Step 4: If you use a straightening staff, you can use it. This effectively levels the plastic, keeping the surface straight and at the same height.

Step 5: Now you have to let the plastic dry according to the manufacturer's instructions. If there is a risk of rain or snow, you must provide protection. The plastic should not get wet as many products are water soluble before drying.

Step 6: Depending on the first shift, you will have to repeat the entire procedure once or twice. This improves the effect of the liquid plastic and enables a straight and closed flat roof seal.

Step 7: Finally, bedding is used if you use it. This has to be done while the top layer is still wet. Finally, you have to let the entire surface dry. Give the coating enough time because this is the only way to keep your flat roof tight.

Tip: The unique thing about liquid plastic is the possibility to choose from numerous colors. With the extensive selection, you can decide in which color your flat roof should shine.

Instructions | Bituminous membrane waterproofing

The classic in terms of flat roof renovation is the use of bitumen membranes, which are laid on the roof and represent an impenetrable layer . The laying of bitumen sheets for a flat roof renovation is used in two different ways using modern techniques.

  • welding
  • cold laying
Bitumen web rolls

The bitumen sheets are laid cold using strong cold glue on the underside, which is attached to the surface. No further utensils are needed per se, since the sheets can be perfectly laid over the adhesive. An adhesive is also used to close the gaps. This variant is mainly used as an intermediate stage. If you still want to use the cold glue bitumen, you can save a lot of time and work.

Cold glue for bitumen sheets

The classic welding technique is more effective, in which the webs are welded together, which offers a good grip. At the same time, this is the much cheaper option, since the sheets with cold glue are significantly more expensive to buy. In addition to the bitumen sheets the size of your flat roof, you also need the following utensils.

  • Gas burner for welding
  • protective clothing
  • Sealing sheets for penetrations or connections
gas burner

If you are not sure how to use the gas burner yourself, you should definitely ask someone for help. Since it is fire, burns can quickly occur if you are not familiar with the operation of the gas burner.

If you like this variant, you have to expect costs of one to five euros per square meter of bitumen membrane. You have to choose welding track bitumen in the shop. Without this addition, you run the risk of purchasing unsuitable bitumen sheets that cannot be welded. Once you have all the materials and tools available, do the following.

Step 1: If you have old bitumen membranes on the flat roof, you must remove them first. Since welded bitumen sheets cannot be easily removed, you either have to use a flame device or a carpet stripper. While the bitumen sheets are heated and removed with the flame device, the carpet strip removes them via sharp blades.

After that, you need to clean the floor and bring it to the same height. The bitumen sheets must not be disposed of with household waste and belong in a recycling center or must be picked up by a professional. You cannot even store the used roofing felt for a long period of time.

Flat roof with bitumen membranes

Step 2: Never place fresh bitumen sheets on worn ones. This can increase the risk of fire and weight, which can quickly become a problem. For this reason, always use a new flat roof seal. Fix the sealing sheets in the necessary places before laying the bitumen sheets. After that it's too late.

Sealing sheets on the flat roof

Step 3: Start laying the first bitumen sheets from your starting point. The side of one of the bitumen sheets is heated and connected to the floor to create a starting point. If you do not have a gas burner available, you can borrow it from hardware stores, specialty shops or even from a neighbor. Depending on the offer, these prices can range from 20 to 40 euros per day.

Bitumen roof sheet roll

Step 4: Lay the sheets using a system that covers the entire flat roof. Flat roof renovation works best when the sheets are close together, as this makes it easier to weld. Each subsequent bitumen sheet is also welded and then pushed off with the foot so that the roll can cover the necessary area.

Lay bitumen sheets

Step 5: Cut the sheets after laying if they do not fit completely. This is particularly recommended if the flat roof has no normal shape or objects as an obstacle. The remains are disposed of together with the used bitumen.

Cut bitumen sheets

Step 6: Now weld the individual sheets together using the weld seams. This can take a while, depending on the size of the roof, which affects the amount of sheets for the flat roof waterproofing.

Make sure that the sheets do not shift, otherwise the flat roof will not become tight. For this reason, be as thorough as possible in this step. Even several people can work together here at the same time.

Weld bitumen sheets

Step 7: The bitumen sheets are simply laid over the sealing tapes and, depending on your taste, you can use liquid bitumen to match the edges in color. Depending on the type of use, this can sometimes be necessary, especially if you spend time on the flat roof.

Step 8: Then a second layer of bitumen is laid on the finished one. However, this must be laid across the other. This is the only way that no moisture can get through the webs. If necessary, a third layer must be installed.

Flat roof renovation with bitumen membranes is time-consuming and it is therefore always recommended to work in a team. If this is not possible, choose a day on which you have sufficient time for this project and on which it does not rain.

Note: There is still the option of laying bitumen rolls directly in liquid bitumen, which requires a lot of effort and a lot of experience. Nowadays, this method is hardly used anymore and it is too difficult for private consumers.

Instructions | EPDM rubber Roofing

A separate flat roof renovation is also possible using EPDM rubber. EPDM rubber (ethylene-propylene-diene rubber) is mainly used to seal flat roofs and similar structures. It is often used when the roofs are to be planted or filled with gravel.

Green roofs

They are also used for garden ponds. The foils are very hard-wearing and can therefore be used for this.

Construction of an inverted roof

The other properties of EPDM rubber flat roof waterproofing are:

  • damp-proof
  • weatherproof
  • high elasticity
  • resistant to numerous external influences such as UV or printing
  • durable
UV radiation, sun


The foils are available for ten to 15 euros per square meter, which puts them in the same price category as the bitumen sheets. In addition to the foils, a special adhesive is required, which in most cases can be purchased from the same dealer. The prices differ very much here.

Other utensils are:

  • Cuttermesser
  • Brooms with strong bristles (street brooms)
  • Gloves and protective clothing
Brooms with strong bristles

Since this film is glued, you need protective clothing . To make it easier to lay them, gloves are recommended so that the film does not slip. As soon as you have enough film available, follow these instructions to effectively seal and renovate your flat roof.

Step 1: Before you lay foil, you have to clean the roof. You can then lay the film so that the entire flat roof is covered. Cut all edges back to a length of about 15 centimeters. The film then rests for a period of at least 30 minutes. This fixes the shape and helps keep it from shifting.

Step 2: Now turn half of the film over completely and apply the adhesive evenly to the roof. Knock back half of it and use the broom to flatten the foil. The other half is glued in the same way.

Lay the flat roof seal

Step 3: Finally, the edges are designed according to your taste. The glue should be dry during this time. Finally, you should pay attention to the manufacturer's information on the drying times, which are listed on the adhesive. This way you can be sure when it is accessible.

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