Exterior Caulking near you

Read clause 7.5.6 in order and the hierarchy is obvious. First, the opening must be flashed, and the flashing material must comply with AS/NZS 2904. Second, the flashing has minimum dimensions: extending not less than one hundred and ten millimetres beyond the reveals, overlapping not less than seventy-five millimetres in the direction of flow. Third, and only then, sealant goes between the laps. Nowhere does the provision offer sealant as an alternative to the flashing.

That has a direct practical consequence for anyone buying exterior sealing work. If the reason the wall is wet is that the flashing is missing, short, wrongly lapped or lapping against the flow, no amount of sealant will fix it, because the water is arriving behind the sealant rather than in front of it. The bead will hide the symptom for a season or two and the damage behind it will continue.

There is a second place the Code touches sealant, and it is about chemistry rather than water. Part 8.2 on windows and external glazed doors requires packing to be clear of any flashing material, and refers to isolating materials such as bituminous membranes or paints and caulking compounds where an aluminium sill contacts masonry. That is a compatibility function: keeping two materials apart, not keeping water out.

Ultraviolet exposure and heat cycling are the obvious pair. An exterior joint on a north or west elevation goes through a large daily temperature swing and sits under intense sun, and every sealant has a finite service life under those conditions. A joint that looks intact from the ground can be chalked, crazed and debonded at the edges when you get close to it, which is why exterior sealing is a maintenance item on a cycle rather than a permanent fix.

Movement is the less obvious one and the more common cause of early failure. A joint between two materials that expand at different rates has to accommodate that movement, and a sealant applied too thin, too wide, without a backing rod, or adhering to three sides of the joint instead of two will tear rather than stretch. Most of the failed beads on Australian houses failed mechanically, not chemically.

Then there is the substrate. Sealant will not adhere durably to a chalking painted surface, to a dusty render, to a damp masonry face or to a dirty metal flashing, and reapplying over old sealant compounds the problem. If the proposal is to run a new bead over the existing one, ask why, because the honest answer is usually that removing the old one is the slow part of the job.

Diagnosis first, and it is the step that gets skipped. Establish where the water is entering, which is very often not where it appears. On a window, the head flashing, the sill, the reveal and the cladding junction are all candidates, and only one of them is fixed with sealant. Ask the contractor to say in writing which joint they believe is leaking and why.

Then preparation, which is most of the labour. The old sealant is fully removed rather than trimmed, the joint faces are cleaned back to a sound substrate, a backing rod or bond breaker is installed so the sealant adheres to two faces and not three, and a primer is used where the sealant manufacturer specifies one. A joint that has been prepared properly looks like a proper joint before anything is gunned into it.

Then application and tooling to a consistent profile, and then, importantly, documentation. Ask for the product name and data sheet, the joint dimensions used, and photographs of the prepared joint before filling. On a repeat problem that record is what tells the next contractor whether the previous attempt was a failure of product, of preparation or of diagnosis.

Resealing is the right call when the joint is doing its designed job and the material has simply reached the end of its life: the flashing behind it is sound, the substrate is sound, the movement is within what the joint was designed for, and the sealant is chalked, split or debonded. That is ordinary maintenance and it should be planned rather than triggered by a leak.

It is a delaying tactic when the water is arriving from behind. A missing or reversed flashing, a lap running against the flow, a sill without a drip, a penetration never collared, or ground built up above the cladding clearance are all faults that sealant conceals. The Housing Provisions set the clearances at the base of cladding and the flashing dimensions at openings precisely because those are the defences, and sealant is not one of them.

The honest test to apply to a quote is whether it names the water path. A quote that says it will reseal the windows has described an activity. A quote that says water is entering at the head flashing lap on the western elevation, that the lap will be reformed and the lap sealant renewed, has described a repair. Only the second one can be compared against a second opinion.