Zuid-Holland · approx. 55 km from Utrecht
Sealant work in Leiden
Within the ring canals Leiden is built close together, with water running through the city. Behind the facades the buildings have been divided into rooms, and beneath them the ground is sinking. Outside the ground is on the move, inside the damp lingers. Those two determine almost every joint we replace here.
Since 1959
Experience and craftsmanship from Utrecht
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Short lines, clear agreements
100% satisfaction
We only leave once you are satisfied
Lasting quality
Top-quality materials for a long-lasting result
What matters in Leiden
Old buildings full of rooms, on soft ground
A dense historic core with many subdivided buildings, belt districts from the thirties, polder districts from the seventies to the nineties, and new builds with glazed aluminium frontages at the Bio Science Park.
In the city centre seventeenth- and eighteenth-century buildings stand shoulder to shoulder: bluestone front steps and sills, timber window frames, and bathrooms that were built in later. The Burgemeesters- en Professorenwijk is largely thirties, with timber window frames that the painter goes over. The Merenwijk was handed over from 1971 onwards and kept growing into the eighties: deck-access flats in the Slaaghwijk, home zones around them, so access decks, concrete joints and expansion joints. The Stevenshof is eighties and nineties, with timber and plastic side by side. PVC expands six to eight times as much per degree as concrete.
Leiden stands on soft ground, and many old buildings stand on timber piles. Building parts do not settle evenly here: the rear house differently from the front house, the extension differently from the house it is built against. A connection joint is therefore subject to more movement than the joint lets on. Here the joint width follows from that movement and not from the eye: 8 mm is the lower limit, and between two building parts it becomes more.
With the van, Leiden is a city apart. In the city centre a zero-emission zone for vans and lorries has applied since 2025. In the low-traffic part you may load and unload on the Breestraat, the Haarlemmerstraat and in Hartje Leiden from Monday to Saturday between half past four and eleven in the morning, although Saturday in Hartje Leiden is restricted by the market. Other streets have other times, so we check those per address. You park in a car park within walking distance; on the street in the low-traffic part there is almost nothing left. So everything goes inside in one go, and we ask in advance which substrates there are. If we turn up with the wrong sealant, the van cannot get back in after eleven.
From Utrecht it is 55 kilometres by road, via the A12 and the N11. Because loading and unloading here has to happen early in the morning, we ask you to bundle the work as much as possible: one address where there is more to do, or addresses that lie close together. One single joint is possible too; then tell us how many metres it is.
What we do in Leiden
- Bathroom, sanitary & kitchenSealing of sanitary ware, showers, baths, washbasins and kitchens.
- Window frames & glazingNeat, durable sealant work around window frames and glass.
- Facades & structural jointsFacade joints, connection joints and expansion joints in floors and walls.
- Swimming pool & wellnessSealant work in swimming pools, saunas, steam rooms and spas.
- Renovation & maintenanceSealant work during renovation, repairs and periodic maintenance.
- Specialist sealant workFor specific requirements and specialist applications.
You will hear from us within 15 minutes on working days, and the work comes with a 2-year guarantee.
The work here
What we do most often in Leiden
Bathrooms in room lets
In a subdivided building four or five people shower one after another in the same room. The wall never gets dry and the anti-mould agent in the sealant becomes exhausted. We replace the joint in silicone with fungicide, because acrylic disperses under prolonged exposure to water. And we tell you what the extraction has to do.
More about this serviceWindow frames and sills on the canal
On the quayside there are timber window frames in brickwork, usually with a bluestone sill beneath. Two substrates within half a metre, so two products: on natural stone only natural stone sealant, on painted timber something that remains overpaintable. Silicone cannot be overpainted, so acrylic or an overpaintable hybrid goes in there.
More about this serviceLabs at the Bio Science Park
On the west side there is work in laboratories, cleanrooms and plant rooms: joints that have to withstand cleaning and that nothing may get behind. There the build-up matters more than the colour. Backing rod in, the joint to depth (width divided by three plus 6 mm) and a product that suits both the substrate and the cleaning agent.
More about this serviceHow we approach it here
Which sealant on what, and what it costs
The substrate decides the sealant
Four substrates come up most often here. Bluestone at front steps and sills in the old city: that calls for natural stone sealant with chemically bound plasticisers. Free plasticisers migrate into the pores and leave a dark edge that only appears after weeks and never comes off again. Painted timber in window frames: silicone is not overpaintable, so acrylic or an overpaintable hybrid goes in there. Glazed tiling in the bathrooms: silicone with fungicide, because acrylic disperses under prolonged exposure to water. And concrete and powder-coated aluminium at the deck-access flats and the new builds: acetoxy silicone does not belong there, because on alkaline concrete it loses its adhesion. Which sealant goes in depends on what it has to adhere to. S 125 is the standard, not an automatic choice.
Costs and lead time
Here the sliding scale only becomes visible with a whole access deck at once. In the Merenwijk the connection joints, the concrete joints and the expansion joints of a row of homes run on one after another; that is one job, and the price per metre comes down there. A single sill on the canal is at the other end of that same sliding scale: there the journey weighs more than the joint. The price is per linear metre and the sliding scale depends on the size of the job. You will not see amounts here: the rates have not been fixed yet, and a price that is different tomorrow is no use to you. Replacement works out higher than new. The old sealant has to come out completely first and that cutting out is the work. It is also the reason we put nothing over old residue: the work comes with a 2-year guarantee, and on residue a joint does not last those two years. For planning, the curing counts too. Sealant cures at roughly 2 to 3 mm per day, so after a sanitary joint there is no showering for two days. If a whole building shares one shower, we do not schedule all the wet rooms on the same day. Say in your request how many metres it is, what the substrate is and whether a shower has to stay in use. You get a reply within 15 minutes on working days, and that helps with scheduling.
Two routes
Business or homeowner in Leiden
Managers and landlords of subdivided buildings work in rounds: the wet rooms of a building in one go, with a list to go with it. We set up our planning around that form. On listed buildings in the old city the painter goes over the joint, so it has to be overpaintable and dry in time for his turn. If you ask us for planned maintenance on the deck-access flats or for new builds at the Bio Science Park, it is about connection joints, expansion joints and cleanrooms, fitted in between other crews. Tell us when your crews are on site and we plan our day around that. If we work under a main contractor, the invoice goes out with the VAT reverse charge.
For businesses
Contractors, painters, homeowners' associations, property managers and interior fit-out.
See what we do for businessesAlso near Leiden
As the crow flies from the centre. By road it is further.
- Oegstgeest 4 km
- Leiderdorp 4 km
- Voorschoten 5 km
- Zoeterwoude 5 km
- Warmond 6 km
- Sassenheim 7 km
- Katwijk 7 km
- Wassenaar 8 km
Is your town or city not listed? See the whole service area.
Questions from Leiden
What people in Leiden ask most often
The sealant in my shower is black again within six months. How is that possible?
Rarely the sealant itself. In a subdivided building the shower is often in a former room without a window. Between two showers the wall never gets dry, and then the anti-mould agent in the sealant is used up within a few months. Putting bleach on it does not help: that removes the black colour and that agent too, and the edge is left more porous than it was. We replace the joint, but we look at the extraction first, otherwise you are back there in six months. For a new bathroom the Dutch building decree (Bbl) sets that requirement at 14 dm³/s.
We let rooms in several buildings in Leiden. Can that be done in one round?
Yes. If you put several buildings into one job, the sliding scale runs over the total number of metres and the price per metre comes down. Provide a list with, per building, the number of wet rooms, and whether the sealant is to be replaced or is new. Replacement costs more, because the old joint has to come out completely first. That gives one price per metre.
The rear house is cracking away from the front house. Does sealant help against that?
Sometimes, but only if the joint is wide enough. Two building parts that settle differently move more than a narrow joint can cope with. If the sealant cracks in the middle of the joint, that is called cohesive failure: the joint was designed too narrow and refilling solves nothing. Count on at least 8 mm wide, with a backing rod behind it so that the sealant adheres on two sides only and not on three. One thing about the guarantee: settlement and movement of the structure fall outside it, because sealant does not hold back a sinking building. What we do is measure the joint against the movement that is there, and say in advance if a joint is not going to carry that movement.
Our front steps on the canal are bluestone and the stone has turned dark along the sealant. Can we still get that out?
No, that is in the stone itself. Plasticisers from the sealant have migrated into the pores; that is called edge-zone staining and it often only appears weeks later. Scrubbing gets nothing out, and a harsh cleaner eats the top layer open further so that the stain stands out even more. Prevention is possible, and only beforehand: natural stone sealant in which the plasticisers are chemically bound, so that they do not migrate freely into the stone. Acetoxy silicone does not belong on natural stone in any case. That is why we always ask about the substrate, even when it is about one sill.
Our building is a listed building with old window frames. Can that sealant simply come out?
Not just like that, and that is down to the age of the window frames. Glazing sealant and putty that went in before 1994 are suspected of containing asbestos and such work falls into risk class 2 as standard. Leiden's city centre within the ring canals is a protected townscape and the city has over 1200 national listed buildings, so the chance of such frames is high here. We cut nothing out until it is established what is in it. If it turns out to be suspect, a licensed asbestos removal company takes it out and a notification is made beforehand. After that we apply the new joint. Because the painter goes over such frames, we choose something overpaintable: silicone cannot be painted.
