Silverfish in the house? Why they are a sign of an underlying damp problem

The silverfish, also known as Lepisma saccharina, is a small, wingless insect belonging to the order Thysanura, a group of wingless insects. They are nocturnal creatures that hide away during the day in the dark nooks and crannies of your home. As such, they only emerge once it gets dark indoors.

In your damp flat they go in search of food rich in carbohydrates, starch and sugars. We’re not talking about the sort of food we eat, but things like wallpaper paste, cardboard, glue and skin flakes. What many people don’t realise is that silverfish are microscopic mould on your walls, in the corners of the room and on the ceiling. They do not bite, do not carry diseases and do not damage the load-bearing structures of your home, but the presence of silverfish can quickly make your home feel unhygienic and may cause minor damage to your wallpaper.

How can you spot silverfish in your home?

You can recognise a silverfish in your home by its specific characteristics.

• Appearance: they are 7 to 12 millimetres long and have an elongated, teardrop-shaped body that tapers towards the rear.
• Colour: their bodies are covered in shiny, silvery scales that glisten in the light.
• Anatomy: they have two long antennae at the front and three distinctive antennae at the back that look like threads.
• Movement: they have no wings, but move quickly with a characteristic, snake-like wriggling motion.
• Location: you’ll almost always find them along the skirting boards, under your cupboards or around the drains in wet areas such as the bathroom, the toilet, the cellar or the laundry room.

Note: Do not confuse the silverfish in your home with booklice. Booklice are duller in colour, larger and thrive in dry, warm places where they gnaw at your books and documents. The silverfish always moisture in the house required.

Why do you find silverfish in your home?

Silverfish don’t just turn up in your home by chance. They are actually attracted to damp areas, which provide the perfect living environment for them. The main reason for their presence in the home can be traced back to three factors.

1. Excessive humidity: silverfish have thin skin and dry out quickly in a dry environment. That is why they relative humidity They need at least 70% to 80% in the home in order to survive and reproduce.
2. Presence of mould: damp walls, corners and skirting boards provide the ideal surface for invisible fungal spores in the house. For silverfish, this is an irresistible source of food.
3. Sufficient shelter: poorly finished skirting boards, gaps between tiles, worn-out sealant edges and cavity walls provide the ideal – and, above all, dark – hiding places where they can let their eggs hatch undisturbed.

In short: Do you regularly spot silverfish in your home as evening falls? If so, that’s a clear sign that the indoor climate in that particular room is too damp and that there may be an underlying moisture problem.

Silverfish cannot survive in a dry room or home. Their thin exoskeleton offers them little protection against dehydration, meaning they are constantly dependent on high relative humidity in-house capacity of at least 70% to 80%. If you regularly spot silverfish in your home, it’s never a coincidence. It’s a direct indication of an underlying moisture problem in the home. But not every damp problem is the same. At AquaConsult, we’ve found that silverfish are attracted by a wide variety of situations.

• Condensation and poor ventilation: everyday activities such as showering, cooking, drying the washing and even breathing produce litres of water vapour in the home. Without a properly functioning ventilation system This moist air cannot escape. It then condenses as condensation on your windows, walls and ceilings. If you then spot silverfish in the bathroom, kitchen or bedroom, this indicates that the humidity in the indoor air is consistently too high. The condensation moisture creates microscopic fungal spores on the paint and sealant edges of your walls, which are the silverfish’s favourite food source.
• Rising damp: when the foundations of your home are no longer properly protected by a physical water barrier, the walls on the ground floor soak up groundwater like a sponge. Do you tend to see silverfish mainly close to the floor, near the skirting boards in the living room, hallway or kitchen? If so, this is a classic sign of rising damp. Rising groundwater causes the plasterwork and the cavity behind the skirting boards to remain permanently damp. This provides silverfish with a warm, dark and extremely damp environment in which to lay their eggs.
• Damp cellars: cellars and crawl spaces are under constant pressure from the surrounding groundwater. Moisture seeps in through hairline cracks in the cellar walls, the floor slab or the joint between the wall and the floor. A damp cellar In many homes, it serves as the silverfish’s headquarters. As a damp cellar is dark and cool, they can reproduce there undisturbed. They then make their way through pipe ducts, cavity walls and cracks into the living areas above.
• Moisture penetration: Old, damaged or porous external walls allow rainwater to seep through. The rainwater then penetrates deep into the façade until it reaches your internal walls. Do you find silverfish in certain places on your external walls or even on the upper floors of your home? If so, their presence often indicates penetrating moisture. They gather precisely in the places where the façade allows rainwater to seep through, because the wall remains damp there and fungi may form.
• Hidden leaks: a small, invisible leak in a drainpipe, water pipe, underfloor heating or central heating system can cause water to seep into the floor or behind the walls of your home for months without you noticing. Have you suddenly noticed a concentration of silverfish in a strange and, as far as you’re concerned, dry spot – such as in the middle of the hall, under the kitchen cupboards or near a pipe? If so, the silverfish population is actually acting as a leak detector. The constantly seeping water creates a hidden damp spot that silverfish are drawn to in droves.
• Construction moisture in new-builds or major renovations: when building or thoroughly renovating a home, thousands of litres of water are used for concrete, screed and plasterwork. It can take up to one or two years for this moisture to disappear completely from your home’s foundations. Many people are therefore alarmed when they see silverfish in a brand-new home. In new-build homes, their presence indicates trapped building moisture. Because new-build homes are extremely well insulated and airtight, the construction moisture has nowhere to go unless it is dealt with particularly thoroughly and mechanically ventilated will be.
• Thermal bridges and insulation faults: a thermal bridge is a point in the structure of your home where the insulation is interrupted, for example around window frames, concrete beams or joints. The wall becomes much colder at that point than the rest of the room. As a result, the warm indoor air condenses immediately when it comes into contact with these cold spots in the room. Silverfish use these localised damp spots as micro-oases to drink and feed, even when the rest of the room is relatively dry.

At AquaConsult, we do not use temporary chemical treatments to control silverfish in the home; instead, we tackle the root cause of the moisture problem for good. No moisture means no fungi And without moisture or mould, silverfish simply cannot survive in your home.

1. Rising damp: Professional wall injection

• The treatment: we inject a high-quality, damp-proof injection seal at the base of the walls to an impermeable moisture barrier to create.
• The result: the brickwork and plasterwork gradually dry out right through to the core.
• Effect on silverfish: the damp breeding ground behind your skirting boards disappears completely. Their eggs and larvae dry out completely and the silverfish colony dies off.

2. Condensation: Controlled mechanical ventilation

• The treatment: we install a smart and mechanical ventilation system in your damp rooms, which automatically extracts the damp indoor air and replaces it with fresh, filtered and heated outdoor air.
• The result: relative humidity at home, it falls and remains stable at a healthy 40% to 50%.
• Effect on silverfish: mould on the walls and the nests disappear for good. The silverfish’s food chain collapses and the adult specimens are the first to die off, meaning that, over time, the young ones will no longer survive either.

3. Damp cellar: Cellar waterproofing or cellar drainage

• The treatment: we’ll make the cellar walls watertight again using 100% via a basement tank using cement grouting layers or by draining the groundwater in a controlled manner via a pumping system from basement drainage.
• The result: a permanently dry and usable cellar.
• Effect on silverfish: the silverfish colony is destroyed. This puts a definitive stop to the constant migration of silverfish through your pipework into the rooms above.

4. Penetrating damp: Facade impregnation

• The treatment: After cleaning the façade, we apply facade waterproofing Apply a transparent, water-repellent protective coating to the exterior wall.
• The result: the rain then rolls off the façade, whilst the interior wall continues to breathe and is able to dry out.
• Effect on silverfish: the interior walls of your home dry out. Even on the top floors, the silverfish can no longer find damp spots to drink from or take shelter in, causing them to die out.

5. Hidden leaks and building damp: Leak detection and building drying

• The process: we detect hidden leaks in your home using thermal imaging cameras, without any demolition work, whilst our free damp assessment or speed up the drying process in your new-build home with professional building dryers.
• The result: the hidden source of damp is therefore stopped straight away and the structure of your home dries out.
• Effect on silverfish: their secret water oases behind your cupboards, pipe casings or plasterwork will disappear immediately.

Silverfish in the home are much more than just an annoying pest in the bathroom or cellar. They are a direct warning of a excessive humidity or a hidden moisture problem in your home. Carrying on spraying with chemical products or setting traps will, in the long run, only cost you money and cause a great deal of frustration. You’re only treating the symptoms of an underlying damp problem. Only when you tackle the source of the damp once and for all will the silverfish in your home disappear and dry out of their own accord. Ready to say goodbye to damp and silverfish in your home for good? Then don’t keep faffing about with temporary fixes. Let our experts carry out a thorough analysis of your damp problem. They’ll visit you, with no obligation, anywhere in Flanders for a free expertise.