How to work with construction foam in hard-to-reach places
Everything always looks so simple in the pictures and operating instructions. Shake the can of construction foam with the valve pointing downwards, screw the gun or adapter tubes onto it and start working in the perfect position with the outlet valve pointing downwards.
But what if you can't hold the can perfectly? For example, if a hole in the ceiling needs to be filled with foam or the area to be filled is difficult to reach for some reason? Here you can help yourself with a few tricks. You can find the most important ones here:
What should I do if I cannot hold my PU foam can with the valve pointing downwards, e.g. when working under a ceiling?
Ideally, construction foam cans should be used "upside down", i.e. with the valve pointing downwards. The reason for this? Unlike classic aerosol cans, PU foam cans do not have a riser tube that transports the liquid contents to the outside when the spray head is actuated. Because PU foam is viscous, such a transport tube would clog. The can must therefore be emptied "upside down". The viscous mass sinks to the bottom and there is always sufficient PU foam at the valve opening.
However, if you want to work directly under the ceiling, you don't need to worry too much. Cans that are held with the valve facing upwards also work with these seven tips:
- Use a PU foam can that has not yet been opened.
- Use fresh construction foam if possible. This can be identified by shaking the can. The more liquid the contents, the fresher the PU foam.
- The PU foam can should be warm. That means around 25 degrees Celsius. The contents are then more fluid and come out more easily. But CAUTION: Never heat a PU can quickly, otherwise the pressurised gas will expand too quickly and the can may explode!
- Shake the PU can very well before use so that the contents mix well. This improves the quality of the emergent PU foam.
- Open the valve fully.
- Repeat shaking from time to time during work.
- Use a small construction foam can if necessary. The smallest 1-component PU foams are available in 150 ml cans. The next largest hold approx. 300 ml. 400 and 500 ml are also OK. 750 - 850 ml cans are too large for such tasks.
If you follow these tips, you should be able to carry out your work without any problems. However, slightly more residue than usual will remain in the PU foam can.
Filling deep holes or pipes with construction foam - here's how!
During renovation or refurbishment projects in particular, there are often pipes that have become superfluous and need to be backfilled. The PU foam can is handy for this! But even with this seemingly simple application, you should follow a few tips so that you can be satisfied with the result.
1. Choose the right foam
A standard assembly foam for sealing and filling is sufficient for this type of application. But you can also use most other foams. Above all, it is important that the selected construction foam has at least fire protection class B2. This fire protection class is generally achieved by all foams sold in Germany. Only a few sewer foams, which are designed for use underground, sometimes only have fire protection class B3. So if you have a sewer foam in your hand, it is worth taking a look at the label or the product data sheet.
If you have a foam gun, you are well advised to work with it and choose a gun foam. Here you should make sure that the gun matches the foam. If you only rarely work with construction foam and don't want to buy a PU foam gun, you can also use an adapter foam.
2. Clarify what is at the other end of the hole
Before you start, you should ask yourself what is at the other end of the hole. Is it possible that the hole on the other side has an exit from which the foam can escape? Do I have to make sure that the foam does not spread unimpeded? If a wall opening leads to the outside, for example, PU foam alone is not enough to seal the hole properly. Further work steps are then necessary.
If you only want to fill a certain part, you can fill the hole or pipe to a certain depth with a round cord made of foam and then insert the filling foam. This ensures that the foam is only prepared in the part you have specified.
3. Mask off the areas that should not come into contact with the foam
Mask off everything around the hole that should not come into contact with the foam. This saves you from having to carry out tiresome cleaning work later on.
4. Work in layers
PU foam needs (air) moisture to harden. If there is not enough water, the foam collapses and a cavity remains. It is therefore best to wet the slot to be filled and the freshly applied foam with water, for example using a water atomiser.
If you want to work with depth, for example to fill a deep cavity, you should apply the foam in layers and wet each layer with extra water. You do not need to wait for the foam layer to harden before you continue working - simply dust the fresh foam with water and continue working. It is also good to pause for between one and three minutes before applying the next layer.
5. Leave some space
Even if it is difficult, you should not foam joints or holes too much because PU foam will continue to expand. With adapter foams, the joint should be filled to approx. 50 percent, with gun foam to approx. 70 - 80 percent. The product data sheet will also inform you about the expected subsequent expansion.
Structural conditions make work more difficult? This can help!
What do you do if you want to fill a hard-to-reach area with PU foam? One option is to simply extend the spray tube on the can with a piece of hose. PVC hoses, for example, which are available by the metre in any DIY store, are suitable. Simply put a piece of hose over the top of the spray pipe and extend the pipe. Experience has shown that an extension of up to a maximum of one metre is possible. However, the foam quality can suffer with this procedure because the can contents are adapted to the length of the spray tube.
