CT1 OB1 is a solvent-free hybrid polymer sealant and adhesive that bonds and seals in one go. Works on wet surfaces, sticks to almost anything, and won’t crack or shrink. Available in a wide range of colours to suit most finishes.
Colour
Price
QTY
Silver
£6.95£8.34
Terracotta
£6.95£8.34
Clear
£6.95£8.34
White
£6.95£8.34
Black
£6.95£8.34
Grey
£6.95£8.34
Brown
£6.95£8.34
Oak
£6.95£8.34
Beige
£6.95£8.34
Anthracite
£6.95£8.34
The CT1 OB1 hybrid sealant and adhesive is one of those products that genuinely earns its place on the van. It handles bonding and sealing in a single application, removing the need to carry separate tubes of silicone, acrylic, mastic, PU adhesive, and butyl rubber sealant. One product doing the work of several is not a gimmick here — it actually delivers on it.
The hybrid polymer formulation is solvent-free, which means it stays flexible once cured and will not crack or shrink over time. That alone puts it ahead of a lot of standard sealants that look fine on day one but start pulling away from the substrate within a year or two. OB1 holds its shape, and the bond it forms is genuinely strong — suitable for structural sealing tasks and adhesive applications where you need confidence in the joint.
Where CT1 OB1 Gets Used on Site
One of the more useful qualities of this OB1 sealant is that it can be applied to wet surfaces. If you are working outside in changeable weather, or sealing around wet areas in bathrooms and kitchens, you are not waiting for conditions to be perfect before you can press on. It also adheres to a wide range of surfaces including timber, metal, glass, concrete, stone, ceramics, and most plastics, so you are not constantly second-guessing compatibility.
It has built-in resistance to fungal and bacterial growth, which makes it well suited to wet room environments and anywhere condensation is a regular issue. No need to reach for an anti-mould silicone separately.
Colour Options
OB1 comes in a useful spread of colours: white, clear, grey, black, brown, beige, anthracite, silver, oak, and terracotta. That covers most window and door frames, kitchen and bathroom installs, roofline work, and general interior finishing without having to compromise on the final appearance. Matching the sealant to the finish takes two seconds off the shelf rather than a special order.
At this price point, it is worth keeping a few colours stocked. The OB1 hybrid sealant and adhesive is the kind of product you reach for without thinking — which is usually the mark of something that actually works.
Pro Tip: When gunning OB1 onto a wet surface, cut the nozzle slightly smaller than you think you need — the hybrid polymer spreads more readily than silicone and a smaller bead gives you better tool-off without mess.
CT1 OB1 is used across a wide range of trades wherever bonding and sealing need to happen together. Joiners and kitchen fitters use it around worktops, sinks, and units. Plumbers and bathroom installers rely on it around baths, shower trays, and wet room panels where a sealant with mould resistance is needed. Roofers and general builders use it on external sealing jobs where weather resistance and adhesion to damp substrates matter.
Window and door installers find it particularly useful for sealing frames to masonry, as it bonds and weatherproofs in a single application. It also sees regular use in flooring, glazing, and general maintenance work where a solvent-free, flexible adhesive sealant is preferred over more brittle alternatives.
Best For
Bathroom and kitchen sealing
Window and door frame sealing
Wet room installations
External sealing on damp surfaces
General bonding and adhesive applications
Roofline and external maintenance
Compatible Surfaces
Timber and MDF
Metal and aluminium
Glass and ceramics
Concrete and masonry
Stone and slate
Most plastics and uPVC
Key Properties
Solvent-free hybrid polymer formula
Will not crack or shrink
Applies to wet surfaces
Anti-fungal and anti-bacterial
High bond strength
Flexible when cured
Available in 10 colours
Not suitable for: Not suitable for use on EPDM rubber or bitumen-based surfaces without checking compatibility first. Not recommended as a structural load-bearing adhesive where engineered fixings are specified.
Cut the nozzle to the bead size you need and load the cartridge into a standard skeleton gun. Apply at a steady pace, keeping the gun at a consistent angle to the joint. OB1 tools off cleanly with a wetted finger or tool within a few minutes of application, so work one section at a time rather than gunning the whole run first.
Surface preparation makes a real difference. Remove any old sealant, loose material, or grease before applying. On porous surfaces a light clean is usually enough. The product will cure in most conditions, including damp ones, but a clean substrate always gives a better finished bond than a dirty one.
Remove all existing sealant or adhesive residue from the substrate
Clean the surface and remove any grease, dust, or loose material
Load the cartridge into a standard skeleton gun and cut the nozzle to suit the required bead size
Apply a consistent bead to the joint or bonding area in a single steady pass
Tool off immediately with a wetted finger or jointing tool to achieve a neat finish
Allow to cure fully before exposing to water or stress on the joint
Can CT1 OB1 be applied outdoors in wet conditions?
Yes. One of the practical advantages of OB1 is that it can be applied to wet surfaces and will still cure and bond correctly. This makes it genuinely useful for external work where waiting for a dry day is not always an option. Just make sure the substrate is structurally sound and free from loose debris before applying.
Does OB1 replace both adhesive and sealant, or is it better at one than the other?
It handles both functions properly. The hybrid polymer gives it a bond strength that replaces most PU and wood adhesives for general fixing work, while the sealant properties are on a par with silicone and acrylic for weathering and gap filling. That said, it is not a substitute for mechanical fixings or specialist structural adhesives where those are specifically required by a design.
CT1 OB1 is based on a hybrid polymer chemistry that combines the flexibility of silicone with the paintability and adhesion of polyurethane, without the solvents present in many traditional sealants. The cured material remains permanently flexible, resists UV degradation, and contains agents that inhibit fungal and bacterial growth. It is compatible with the vast majority of common construction substrates and requires no primer on most surfaces.
Brand
CT1
Formula Type
Hybrid Polymer
Solvent Content
Solvent-free
Application Surface
Wet or dry
Fungal and Bacterial Resistance
Yes
Available Colours
Anthracite, Beige, Black, Brown, Clear, Grey, Oak, Silver, Terracotta, White
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