Roof renovation - Frequently Asked Questions

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Polyurethane in-situ foam

In our experience, how long does a foamed roof last?

Polyurethane foam is not UV stable. In practice, this means that the sun would slowly destroy the foam if it is not protected from UV exposure. As long as the UV protection is intact, the foam does not change.

ISOPOL uses only long-term products with building approval! This also applies, and in a special way, to the UV protection: PURELASTIK. For the customer, who usually has to rely on the word of the processor, the ongoing quality assurance in the form of in-house testing and external monitoring by the State Materials Testing Institute MPA in Dortmund is the guarantee for an optimal end product. We consistently implement new findings!

The oldest foamed roofs are about 40 years old. By the way, old foam roofs, which are still treated with conventional paint coats, can be re-treated with PURELASTIK in most cases!

Can a foamed roof be walked on?

In principle, yes. A roof must be accessible for maintenance and inspection purposes. When walking on it, however, care should be taken to ensure that footwear with the softest possible soles is worn. If, for example, a ladder is to be placed on the roof, load distribution (boards) must be provided under the ladder.

Is it possible to foam a roof terrace and use it as such?

In principle, yes, but precautions must be taken to ensure that the foam is not mechanically damaged. Here, for example, wooden floors are suitable as a useful surface or stone slabs laid on sand-filled bags. Point loads from tables and chairs must be avoided.

What influence does foaming have on the statics?

As a rule, none. When foaming roofs, the weight per unit area per m² is increased by about 2.5 kg. However, since the foam is in principle self-supporting, in many cases the statics is rather improved. With foaming, a composite element is produced.

Is the polyurethane foam waterproof?

Yes. The finished foam is waterproof, but has excellent diffusivity (breathable). With proper processing, the max. water absorption is 5Vol.%.

Is polyurethane foam hazardous waste in case of demolition?

No. Polyurethane foam is made from 2 components. After the reaction of the two components, the foam is chemically completely neutral. When it comes to waste disposal, it is treated like ordinary household waste.

Does polyurethane foam contain substances that are harmful to health?

No. The finished foam is chemically completely neutral. It does not contain any substances that can leak out over time and cause damage to health. By the way: Polyurethane can be found in various forms in everyday use everywhere: as "foam rubber", in vehicle construction (dashboard supports, seats, upholstery, etc.), in medicine (prostheses), industrial flooring, insulation in refrigerators and freezers, etc.

What should be the nature of the substrate?

The substrate to be foamed should be clean (broom-clean is usually sufficient), solid (no loose parts) and dry. Dry is the most important point, because the reaction mixture sprayed on in liquid form would react with moisture.

Can I do foam insulation myself?

No. Processing requires relatively complex machine technology. The foam systems we process are always two-component. Via the processing machine, the two starting raw materials are precisely metered, heated and fed to the spray gun via 100 m long hose lines.

What layer thickness is required?

The coating thickness depends on the desired result. If the goal is reliable waterproofing and thermal insulation is not an issue, a coating thickness of 15 to 20 mm is sufficient; for thermal insulation, the minimum thickness is 35 mm. Any desired coating thickness can be applied, depending on the requirements. If required, the requirements of the EnEV (Energy Saving Ordinance) are of course met with this approved insulation material.

What preparations have to be made on site?

The builder must ensure that sufficient electricity is available: 380V/32A. In addition, the client must ensure that no vehicles are parked in the immediate vicinity during the foaming work. Other on-site services will be agreed with the client on an order-related basis.

Why is my roofer warning me about roof foaming?

There are several reasons for this. It is certainly true that there are foamed roofs that are really not in order. Either the installer has done unqualified work or the roof is still coated with conventional UV protection and this has not been maintained. This often happens, for example, when the object has changed owners and the new owner did not know about the necessary maintenance. Often, however, the reason is that the owner did not see the need for re-coating because, after all, his roof was still tight, and this despite the poor condition of the UV protective coating.
But the main reason for the roofers' warnings is probably that they normally lose a repair customer! A foamed roof with long-term UV protection is largely maintenance-free! Even an old foam roof can be renovated in most cases with a PURELASTIK recoating.
By the way: The most frequent reasons why a builder decides for a roof renovation with polyurethane in-situ foam and PURELASTIK are the unbeatable low price and the annoyance about constant repairs of the conventional roof sealing!

What does "roof sealing thermal insulation" mean?

Here, the sprayed-on polyurethane foam has the function of thermal insulation as well as roof waterproofing at the same time. The great advantage of this method is that the roof surface is thermally calmed to a considerable extent by the insulation on the outside. High heating caused by the sun and sudden rain lead to temperature drops, which now do not affect the roof. The polyurethane foam absorbs the fluctuations.

Do birds peck holes in the foamed roof?

In some regions, and this is quite different in Germany, the issue of "bird pecking" is indeed a problem. On the one hand, the top surface layer should be as elastic as possible, but on the other hand it should also be hard enough to counteract mechanical damage, which is where "bird pecking" comes in. If "bird pecking" is to be feared, we offer to sprinkle a suitable slate chippings into the still liquid PURELASTIK top layer. This is blown evenly into the highly sticky PURELASTIK layer by means of a modified sandblasting blower. The individual particles of slate chippings bond intensively with the coating and form a hard top layer that is unassailable by birds. Good visual appearance and permanent UV protection are pleasant side effects. It is also possible to embed a fleece in the still liquid UV protection PURELASTIK and to recoat it until it is completely saturated. This creates an additional seal in the form of a film on the foam layer.

And what does it cost?

Since every roof is different, the problem and task varies and the environment to be considered is different in each case, a general price cannot really be named. Therefore, we have switched to evaluating and calculating each roof individually. As a customer, you have planning security with our fixed price offer. Further costs, than those shown in our offers, do not arise!

PURELASTIK liquid plastic


PURELASTIK is a liquid plastic that forms a highly elastic, self-adhesive sealing film on the roof. PURELASTIK is absolutely plasticizer-free and is suitable for almost all roof surfaces. The finished coating is seamless and jointless and is characterized by very high elasticity and diffusivity.

How is PURELASTIK processed?

PURELASTIK is a one-component product and can be applied by lambswool roller, brush, broom or airless spraying.

What are the requirements for the substrate?

PURELASTIK can be applied on any substrate that is clean, solid and dry. On porous substrates, PURELASTIK can be applied diluted to close the pores in advance. However, suitable primers, e.g. PURGRUND, can also be used. The individual case must be checked.

How long does PURELASTIK last?

PURELASTIK is resistant to UV radiation. We have had the expected service life tested by the State Materials Testing Office MPA-NRW in Dortmund. When used on roofs with full reinforcement, the expected service life is more than 25 years. You can find the corresponding expert reports under Service/Downloads.

What colors are available?

We recommend the color industrial gray for roofs, which has proven to be particularly good in our widths. Other colors are available on request

Must PURELASTIK be used on roofs with full reinforcement?

The current flat roof guidelines say yes to this. However, this statement requires some explanation. The so-called dry film thickness is of decisive importance with regard to durability. This should not be less than 1.6 mm. In the case of full reinforcement with fabric fleece, this value is always achieved. Without reinforcement, significantly thinner layers are possible and thus also harmful to the roof.

Can PURELASTIK save a soaked foam roof?

Yes, the liquid plastic PURELASTIK from ISOPOL is suitable for this application. However, an individual approach is required here after prior evaluation, possibly combined with the installation of flat roof expansion vents. ISOPOL will be glad to work out an individual proposal for you.

Can PURELASTIK be used for waterproofing balconies and terraces?

In principle, yes. However, special working methods must be applied when waterproofing balconies. If necessary, one of our technicians will be happy to provide assistance. In order to be able to use the surface thus obtained also in the sense of a terrace, a wear layer, e.g. of wood or paving slabs, should be applied to the waterproofing.

Is PURELASTIK comparable to conventional films as a roof waterproofing material?

Conventional foils consist of sheets that are welded to the roof. Fastening to the substrate is either mechanical (e.g. by doweling) or weight (loosely laid with gravel fill). For roof edges and wall junctions, foils are fastened with aluminum profiles.
PURELASTIK is self-adhesive and forms a seamless and jointless film on the roof. Even if damaged, there is no infiltration of moisture. The mechanical and physical properties are quite comparable.

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