Frequently Asked Questions

What is the difference between Nitoseal MS300 and a standard silicone sealant for facade joint sealing?

Standard silicone sealants are excellent for weatherproofing and UV resistance but have two significant limitations for building facade applications. First, silicone sealants cannot be painted or overcoated with facade paints after curing — silicone is inherently non-stick, and paint applied over cured silicone peels away. This prevents the use of silicone in joints that must be incorporated into a painted facade system, or where the joint sealant must match a painted concrete, render, or metal surface. Second, silicone sealants typically require a silicone-specific primer (Sil primer or equivalent) for adhesion to porous substrates such as concrete, masonry, and stone. Nitoseal MS300 MS polymer overcomes both limitations — it is paintable with standard facade paints after curing (allowing the joint to be finished flush with the surrounding surface colour), and it adheres to concrete, masonry, glass, aluminium, and steel without primer on most substrates. For building facades where the joint sealant must be painted and where the architect requires a seamless, coloured joint finish, Nitoseal MS300 is the technically superior choice over silicone.

What joint dimensions should be specified when using Nitoseal MS300 on a concrete facade panel system?

Joint dimensions for Nitoseal MS300 on concrete facade panel systems must be designed to accommodate the full range of anticipated movement while keeping the sealant within its stated movement accommodation capacity. The rule of thumb for sealant joint sizing is: the joint width must be large enough that the maximum anticipated movement does not exceed the sealant movement accommodation rating (plus or minus 25 per cent of the installed joint width for Nitoseal MS300). For concrete panel joints in Indian buildings subject to the full annual temperature range, a thermal movement of 1 to 1.5 mm per metre of panel length is typical. For a 3 m long facade panel, total thermal movement at the joint is approximately 3 to 4.5 mm — the joint width must be at least 4.5 divided by 0.25 = 18 mm to stay within the sealant movement accommodation. A minimum joint width of 20 to 25 mm is therefore typically specified for facade panel joints. The joint depth should be approximately half the width, achieved with a polyethylene foam backing rod of the correct diameter.

Can Nitoseal MS300 be applied in rain or high humidity and what are the minimum substrate preparation requirements?

Nitoseal MS300 is a moisture-curing sealant — it cures by reaction with atmospheric moisture. High humidity actually accelerates the surface skin formation and curing speed, which is generally beneficial. However, the sealant must not be applied to wet or rain-washed joint faces — water on the substrate surface prevents the initial adhesion bond from forming. Joint faces that are temporarily wet from recent rain should be dried with compressed air or allowed to dry surface-dry before application. Application in rain is not recommended as rain falling on fresh uncured sealant can cause surface wrinkling or whitening during cure. The minimum substrate preparation requirements for Nitoseal MS300 are: clean (free of dust, oil, grease, curing compound, and old sealant residue); sound (no loose or weak surface layer); and dry or surface-dry at the adhesion interfaces. A foam backing rod must be installed at the correct depth before application, and a fine masking tape along both joint edges will produce a clean, neat sealant bead appearance after tooling.