Questions
Frequently asked questions
The questions that come up most with sealant work, with an honest answer. Is your question not here? Send us a WhatsApp message or an e-mail; you do not need to request a quote for that.
Since 1959
Experience and craftsmanship from Utrecht
Clear communication
Short lines, clear agreements
100% satisfaction
We only leave once you are satisfied
Lasting quality
Top-quality materials for a long-lasting result
Part 1
Price and quote
What does sealant work cost?
For business clients we charge per linear metre, on a sliding scale: the larger the job, the lower the price per metre. For homeowners we charge per job. You hear the amount in advance, in the quote.
How long is a quote valid?
30 days after the quote date.
How quickly will I get a reply to my request?
We respond to your quote request within 15 minutes on working days. By phone we are available for longer: Monday to Friday 09:00 to 22:00, weekends 09:00 to 17:00. If your request comes in late in the evening or at the weekend, you will have a reply on the next working day. That first reply is a response, not a price: sometimes it is a question back, sometimes a proposal for a site survey.
Do you charge for additional work afterwards?
Only if you have agreed to it. If we come across something during the work that is not in the quote, we call before we continue.
How does VAT work?
If we work as a subcontractor on work of a tangible nature on site, we invoice with the VAT reverse-charged. If you are a private customer or the end customer, we simply invoice with VAT.
What does sealing a bathroom cost?
That depends on three things: how many metres it is, whether old sealant has to come out or the surface is bare, and where you live. Cutting out old sealant takes more time than running a fresh joint, and that time is in the price.
That is why the homepage has a price calculator instead of a single amount: fill in what needs doing and you see straight away roughly where you stand. That is an indication, not a rate. We do not name a fixed amount here: every job is different, and a price we cannot deliver on is worse than no price.
Why is there a minimum amount?
Because a small job consists mostly of travel time. A bathroom is only a few metres of sealant work, but if we have to drive an hour and a half for it, there and back, more time goes into the car than into the work. That does not add up. The minimum amount already includes a number of metres of sealant work and part of the travel costs. It works the other way round too: the more metres, the lower the price per metre. We calculate the discount over the total of the job.
Do you charge travel costs?
We do, and you see them up front rather than afterwards. Up to fifteen kilometres from our base in Utrecht they are included in the price. If you are further away, the price calculator adds the kilometres straight away; beyond forty kilometres we put travel costs and travel time in the quote. If paid parking applies at your address, the actual parking costs are added — you are told that up front as well.
Is the price I calculate myself binding?
No, and that works in your favour. It is an indication. The sealant applicator measures on site and the invoice covers the actual linear metres. So you never pay for metres that are not there.
What if I have estimated the metres wrongly?
No problem. A rough estimate is fine; the sealant applicator checks the measurement. If you are a long way off, you hear that before we start and not when the invoice lands on your doormat. Really not sure? Send a photo with your request and we will estimate it.
Are you the cheapest sealant company in the Netherlands?
No. Nor the most expensive. We charge a price that comes with a 2-year guarantee, carried out by professionals who know the work. The amount covers labour, materials and tools. If all you want is the lowest price, you will find it elsewhere, and usually you end up paying it two years later anyway.
Part 2
The work itself
How long does a sealant joint last?
That varies a lot by location. An exterior joint facing south takes sun, rain and movement; a joint in a porch hardly moves at all. During a site survey we say per building element what we expect, instead of one figure for everything.
Why does mould keep coming back?
Because it is in the sealant, not on it. Cleaning removes the top layer, the rest stays. Chlorine-based and abrasive cleaners make it worse: they wash the mould inhibitor out of the sealant and make the edge porous. Replacing it and ventilating better is the only real solution.
Can new sealant go over the old?
No. Sealant does not bond to sealant. Whatever is smeared over the top comes loose within a year, and then you have two layers to remove instead of one.
How long do I have to wait before I can shower again?
Sealant cures at roughly two to three millimetres per day. A sanitary joint is about six millimetres deep, so allow two days. We tell you that in advance so you can plan for it.
Why does the joint need a backing rod?
So that the sealant bonds on two sides instead of three. If it also bonds to the bottom, the middle cannot stretch and the joint tears at the first movement.
Which sealant do you use?
We work with OTTO-CHEMIE and Soudal, and within those with the top range. The standard choice is OTTOSEAL S 125. But which cartridge comes along depends on the substrate: bonding to glazed tiles is different from bonding to concrete, natural stone, plastic or powder-coated aluminium. The sealant applicator chooses per situation and explains why.
Which sealant products do you work with, and can I supply my own sealant?
We work exclusively with professional sealant products from proven A-brands. For each application we select the right product ourselves for the substrate, the load and the conditions. We do not apply sealant products bought by customers, even if they are still unopened. That is the only way we can safeguard the quality of the material, correct application and our guarantee on the sealant work carried out.
Which sealant belongs on which substrate?
The substrate determines the product. There are three rules where it usually goes wrong. Acetic-curing silicone sealant does not belong on bare aluminium, copper, zinc, lead, mirrors, marble, natural stone, concrete or polycarbonate: on a mirror it attacks the silver layer, on alkaline concrete it loses adhesion. Acrylic is unsuitable for prolonged exposure to water, because it disperses; in a wet room the right choice is silicone or a hybrid with fungicide. And silicone cannot be painted over. If you are not sure what your substrate is, send a photo with your request.
Why does sealant leave a dark edge on natural stone?
That is called edge-zone staining. Free plasticisers and silicone oil migrate into the pores of the stone and leave a dark edge along the joint, often only visible after weeks. It is irreversible: polishing does not help and the stone does not return to its colour. On marble, bluestone, travertine and other natural stone, only natural-stone sealant with chemically bound plasticisers belongs. That is a choice you make beforehand, not afterwards.
Can the sealant be painted over?
Not silicone. Paint does not adhere to it and beads up into droplets. If it has to be painted over, for example a connection joint in woodwork that is still to be painted, then acrylic or a paintable hybrid belongs there. So say in advance that painting is still to come, and the right cartridge comes along.
How wide and how deep should a sealant joint be?
For elastic sealant, 8 mm is the minimum width, according to the VMRG quality requirements. Plasto-elastic 9 mm, plastic 10 mm. If the joint is narrower than that, the sealant cannot handle the movement and tears. The depth follows from the width: width divided by three, plus 6 mm. So a joint 18 mm wide becomes 12 mm deep. The sealant should be thinner in the middle than along the flanks, otherwise it does not stretch with the movement. A sanitary joint is at least 8 mm wide and 6 mm deep. Above 30 mm wide it is no longer an ordinary sealant joint, and we first look at what exactly is moving.
How do you determine the joint width?
From the movement the joint has to take up, not by eye. Every material expands differently per degree of temperature difference: concrete 10 to 12 millionths, aluminium 23 to 24, PVC 70 to 80. That is why connection joints between two different materials take up the most movement. The width follows from that movement. It does not work the other way round: the sealant itself does not take up settlement or working of the structure. If a building element moves more than the joint was dimensioned for, the joint is too narrow and refilling it does not help. We would rather measure that beforehand than afterwards.
What does class 25 on the cartridge mean?
That the sealant achieves 25 per cent deformation in testing, according to ISO 11600. That is a test result, not a design value. How much a joint may move in practice is in the manufacturer's data sheet, and that is what we calculate with. Anyone who uses the class as a design value makes the joint too narrow.
Which backing rod goes in, indoors and outdoors?
Outdoors and anywhere water can reach: closed-cell polyethylene, because it does not soak up water. Indoors, in a dry joint, open-cell polyurethane will do. The difference is also in the oversize. Open cell you choose 50 to 100 per cent wider than the joint, closed cell 25 to 50 per cent, so that the profile stays firmly in place. What never belongs in there: wooden battens, a rubber hose, PU foam from a can and polystyrene. They do not give, or they do not tolerate the sealant.
My joint is coming away at the edge, or tearing in the middle. What does that mean?
Two different problems with two different causes. If the sealant comes away along the flank, that is adhesive failure: the adhesion is gone. Usually because of a dirty, damp or dusty substrate, or the wrong sealant on that substrate. If the tear is in the middle of the joint, it is cohesive failure: the joint is too narrow for the movement placed on it. The second is important to know, because refilling the same joint then solves nothing. A wider joint is needed.
What is an expansion joint?
A joint that is there to take up movement. Building elements expand in the sun and shrink in the cold, and an expansion joint gives them the room to do so without anything tearing. It always needs a backing rod, and the width follows from the calculated movement. Sealant that goes into such a joint without a backing rod bonds on three sides and tears in the first warm week.
Can the slot at the bottom of the window frame be sealed shut?
No. That opening in the sill is a drainage slot, and the rebate under the glass is pressure-equalised: moisture that gets in has to get out again. If it is sealed shut, the water sits against the edge seal of the insulating glass and in time the pane fogs up from the inside. VMRG specifies: at least one opening for a sill up to 600 mm, two for a longer one, 8 mm round or 5 by 25 mm. If you come across a sealed drainage slot, report it, because it should be open.
How do I choose the colour of the sealant?
The sealant applicator carries a number of standard colours and you choose one together. If in doubt, he puts down a sample: a short length in two or three colours, so you can see it in your own light. Still to be filled in: which colours come as standard A colour on a screen is never exactly the colour from the cartridge, which is why the sample.
Part 3
Maintenance
How do I keep the sealant joints clean?
Rinse the joints with lukewarm water after showering. That way no soap and dirt residue stays on the sealant, and that is exactly what mould lives on. Then dry them with a towel and open a window or the door, or let the mechanical ventilation run for a while. It is the moisture that lingers that matters, not the showering itself.
How do I prevent mould in the sealant joints?
With the same recipe: rinse, dry, ventilate. Once the mould is in the sealant, you will not get it out again: cleaning only removes the top. Then replacing it is the only real solution.
What should I stay away from?
Three things. Greasy cleaning agents such as soap leave a sticky layer that dirt and bacteria stick to all the more. Hard brushes, scouring sponges and a pressure washer damage the surface of the joint, and a damaged surface gets dirty faster. And bleach, chlorine or sodium hypochlorite wash the mould inhibitor out of the sealant, and then that sealant no longer does exactly what you bought it for.
Will the sealant then stay free of mould?
No, and we do not promise that either. Mould-resistant sealant inhibits mould, it does not rule it out. If you stick to the above, that effect stays intact much longer. Ventilation matters more here than any cleaning agent.
How much ventilation does a bathroom need?
For a bathroom in a new build the requirement is 14 dm³ per second. That is in the Bbl (the Dutch building decree), article 4.122. In an existing bathroom that is a good yardstick: if your extraction does not achieve that, or there is no ventilation gap under the door, the moisture lingers and no type of sealant has an answer to that. That is also why insufficient ventilation falls outside the guarantee. Let the ventilation run for another half hour after showering.
When should I have the sealant joints checked?
A first check within a year of handover, then every two years. That is the interval the VMRG uses for facade elements. Preferably look in the cold season: the building elements are then contracted and the joint is at its widest, so you see small cracks and loose flanks that are not there in July. This is separate from the guarantee period; it is maintenance, not a condition.
Part 4
Working together
Do you work throughout the Netherlands?
For projects, yes, from Utrecht. For individual jobs at home we keep to roughly 75 kilometres around Utrecht. Further away, more time goes into the car than into the work and a single job is not viable. If you are not sure whether your address falls within that, just ask.
Do you work for homeowners or only for businesses?
Both. On the business side we focus on painting contractors, contractors, VvE property managers, property maintenance and interior fit-out; if we work as a subcontractor, we invoice with the VAT reverse-charged. For homeowners we work at your home. The work is the same, the way of charging differs: business per linear metre on a sliding scale, homeowners per job.
Can you handle a large project?
We start with five people and scale up with self-employed professionals whom we manage ourselves. If you want to know what is feasible on your project, request a site survey and we will work it out for you.
Do you also do fire-resistant sealing?
Yes. We apply fire-resistant joints. Which system goes in depends on the wall and the fire resistance you need, so let us know that with your request.
Do you approach my customers?
Never. If we work for you as a subcontractor, your customer stays your customer.
What if there is asbestos in the old sealant?
Glazing sealant and putty from buildings dating from before 1994 are suspected of containing asbestos. They fall into risk class 2 by default, and that means: no cutting out without further ado. First an asbestos survey, then a demolition notification, then removal according to protocol by a certified company. If we suspect asbestos, we cut nothing out there and report it to you. We do not do that removal ourselves. Once the area has been cleared, we simply apply the sealant.
How do I know whether there is asbestos in the old glazing sealant?
You cannot tell from the sealant itself. It can only be ruled out with a sample: taken by a certified asbestos survey firm and analysed in a laboratory. If you are not sure, assume that it is and have it tested before anyone starts cutting into it. That is cheaper than a room that has to be decontaminated afterwards.
Part 5
Guarantee
What guarantee do you give?
2 years on the work carried out. What is and is not covered is in the quote. For private customers: this guarantee comes on top of your statutory rights and does not limit them.
What is not covered by the guarantee?
Among other things: movement of the structure greater than the sealant can handle, a substrate we did not install (loose tiles, a shower tray with play), joints narrower than 8 mm or wider than 30 mm, mechanical damage, cleaning with chlorine or abrasives, insufficient ventilation, edge-zone staining on natural stone, and discolouration or mould on top of the sealant. We guarantee that the joint is sealed, not that nothing ever grows on it.
What do I have to do to keep the guarantee?
Ventilate and do not use aggressive cleaners. At handover you get brief instructions for that. For exterior work we also recommend a first check within a year and then every two years; that is maintenance and not a condition of the guarantee.
Is movement or subsidence of the building covered by the guarantee?
No. Movement and working of the structure fall outside the guarantee, and that is not in the small print but in the technical facts: a sealant joint takes up the movement it was dimensioned for and not a millimetre more. If the ground settles or the building moves more than that, the joint is too narrow for that situation and it tears, however well it was applied. What we do about it: during the site survey we look at what movement acts on the joint and what width that requires, and we tell you in advance if an existing joint is too narrow for it. Better that conversation beforehand than a dispute afterwards. The 2-year guarantee applies to our work: adhesion and tightness of the joint we applied.
What if I am not satisfied?
Say so straight away, preferably while we are still there. The sealant applicator walks through the work with you at the end; whatever is not right then, he puts right on the spot. That is what our satisfaction policy stands for: we do not leave until you are satisfied. If you notice it later, the complaints procedure in our terms and conditions applies, and the 2-year guarantee on the work itself. Still to be filled in: what exactly the 100% satisfaction guarantee entails
