BT1 vs CT1: Which C-Tec Product Do You Need?

Both come in the same size cartridge. Both are made by C-Tec. Both say TRIBRID on the label. They sit side by side on our trade counter shelf, they are similarly priced, and the name alone does not tell you which one belongs on the job. If you are trying to decide, this is the article that settles it: a full comparison, a clear rule of thumb, and guidance on every situation where the choice is less obvious.

The short answer: CT1 is the universal trade sealant and adhesive for general construction and installation work. BT1 is C-Tec's dedicated bathroom sealant, engineered with enhanced anti-fungal protection for use in wet rooms and sanitary environments. Both products share the same TRIBRID polymer technology and the same application technique. The choice between them comes down to one question: is this a sanitary joint in a bathroom, or is it something else?

BT1 vs CT1: Side by Side

When to Use CT1

Reach for CT1 Sealant and Adhesive when:

• You are bonding across different substrate types (metal to glass, timber to masonry)
• You need to replace mechanical fixings on mirrors, panels or cladding
• The substrate is wet or the conditions do not allow it to dry
• You need a colour other than white or clear
• The joint will be over-painted once cured
• You are sealing cable penetrations, conduit runs or back boxes on site
• The environment is marine or salt-water

When to Use BT1

Reach for BT1 bathroom sealant when:

• You are sealing around a bath, shower tray, basin or wet room
• Mould resistance on the sealant surface matters long-term
• The installation is in a hospital, clinic, school or food-preparation area
• You are bonding shower panels without mechanical fixings (ETAG approved)
• A long-term, hygienic, bacteria-resistant sanitary finish is required

What CT1 and BT1 Have in Common

Both products are manufactured by C-Tec and built on the same TRIBRID polymer platform. That means both bond without primer to the same range of substrates: metal, glass, timber, MDF, fibreglass, concrete, ceramics, uPVC and most plastics (PP, PE and PTFE are the exceptions for both). Both cure without shrinkage or cracking, both are solvent-free and low-emission, and both can be applied in wet conditions. Full cure for each under normal conditions is approximately 24 hours: for more detail on BT1 specifically, see our guide to how long BT1 takes to dry. Application technique is identical: standard cartridge gun, continuous bead, tool immediately with a wet finger.

Because the chemistry is the same, neither product requires a primer, and neither needs mechanical fixings to form a structural bond on compatible substrates. If you are a plumber or electrician who has used one of them before, the other will feel exactly the same in the gun.

Preparing Surfaces Before Applying Either Product

The most common reason a sealant joint fails before its time is poor surface preparation, not a problem with the product. Before applying CT1 or BT1, the joint faces need to be clean, free of grease, and free of old sealant residue.

Old sealant removal is best handled with PeelTec paint and sealant remover. Spray it on the cured sealant, allow it to penetrate, and the old material lifts cleanly without damaging the substrate underneath. This is quicker and less likely to cause surface damage than cutting and scraping alone.

Once old sealant is removed, degrease the joint faces with MultiSolve. In a bathroom this step is critical: soap film, body fat and cleaning product residue all compromise adhesion. MultiSolve removes them without leaving a solvent residue of its own.

Can You Use CT1 in a Bathroom?

Yes. CT1 is waterproof and perfectly suitable for use in bathrooms, as covered in detail in our guide on whether CT1 is waterproof. The distinction is specific: for the sanitary bead around a bath edge, shower tray or basin, BT1 is the better choice, because its enhanced anti-fungal protection prevents mould developing on the sealant itself. That is the most common failure point for bathroom silicone over time, and it is what BT1 is engineered to prevent.

For everything else in a bathroom, such as fixing a shower enclosure panel, mounting a mirror without fixings, or sealing a back box on a tiled wall, CT1 is the right tool. The rule is simple: sanitary bead, use BT1. Everything else, use CT1.

BT1 is available from Harbro in White and Clear. For most bathroom applications, the White variant is the standard choice. The Clear variant suits applications where you want the substrate to show through the joint, such as glass shower screens or transparent acrylic panels. Both versions carry the same TRIBRID anti-fungal formulation and perform identically.

What About FC1 Decorator's Caulk?

If you are also looking at joint filling around skirting, architrave or coving before painting, neither CT1 nor BT1 is the correct product for that application. FC1 Decorator's Caulk is C-Tec's acrylic caulk designed specifically for pre-paint applications: it is paintable in 30 minutes and is formulated to take emulsion without bleed-through. CT1 and BT1 are both polymer-based and not designed for fine decorating use. All three products are available from the Harbro C-Tec range.

Both CT1 and BT1 are in stock at Harbro Electrical in Peterlee. Trade account pricing at checkout. Shop the full C-Tec range.