Window Caulking near you

There is no Approved Document about sealant. What there is sits inside the guidance on installing the window itself. Approved Document L Volume 1 says that for new and replacement windows, roof windows, rooflights and doors, where the entire unit is provided, units should be draught-proofed and insulated cavity closers should be installed where appropriate. Elsewhere it puts the same point more plainly: when installing windows, roof windows, rooflights or doors, all of which are controlled fittings, the controlled fitting should be well fitted and reasonably draught-proof.

That wording matters because it attaches to the installation, not to the sealant. It means the perimeter joint is part of what an installer is signing off when a window goes in, and a job that leaves a ragged or unfilled gap has not met the standard even if the window itself is excellent. If the windows were fitted recently and the perimeter joint is failing, that is a defect in the installation and belongs to whoever fitted them, not to a separate mastic contractor.

Resealing on its own is different. Approved Document L defines a controlled fitting as the entire unit of a window, roof window, rooflight or door including the frame, and work that does not provide one falls outside the energy efficiency requirements. Renewing a bead of sealant plainly provides no unit at all, so no certificate exists and no competent person scheme applies. Treat a firm offering you a compliance certificate for resealing with suspicion.

The work is mostly removal. Old sealant is cut out back to bare frame and bare masonry on both faces of the joint, and the surfaces are cleaned and allowed to dry, which on a British exterior often means picking a dry spell rather than a dry morning. Sealant will not bond to a damp or dusty substrate, and a bead applied over the remains of the old one is simply a decorative strip that will lift within a season.

A joint that is too deep is then backed, usually with a closed-cell foam rod, so that the sealant bonds to the two sides of the gap and not to the back of it. This is the step most often skipped and the reason beads split down the middle: a sealant stuck on three faces cannot stretch as the joint moves, and a window frame and a brick wall move differently every time the weather changes. The bead is then gunned in one pass and tooled to a concave face so that water sheds off it.

Ask what is going in and why. A low-modulus neutral-cure silicone is the usual choice on a frame-to-masonry joint because it stays flexible and does not stain porous stone; acrylic frame sealant is for internal joints that will be painted, and will not survive outside. Any competent contractor will tell you which they are using without being pushed, and the answer should differ between the outside bead and the internal line.

Most of the risk in this job is the access, not the material. The Health and Safety Executive states that the purpose of the Work at Height Regulations 2005 is to prevent death and injury caused by a fall from height, and that if you are an employer or you control work at height, including building owners who contract others to work at height, the Regulations apply to you. Employers and those in control of any work at height activity must make sure work is properly planned, supervised and carried out by competent people, and must first assess the risks.

For a homeowner engaging a contractor, the practical reading is that the duty sits with the firm you hire, and the way to see whether they take it seriously is to ask how they intend to reach a second-floor window before they arrive. A firm that plans on standing a ladder against the frame it is about to cut sealant off has not thought about it. Tower scaffold, a proper ladder tied at the top, or a cherry picker on a tight street are all normal answers.

Two other cautions are worth raising on older stock. Cutting out old paintwork around timber frames on a house that predates the phasing out of lead in domestic paint creates dust you do not want in the garden or the house, so ask how it will be contained. And on a property in a conservation area or a listed building, changing the look of a mortar joint or introducing a visible mastic line where none existed can matter, so check before the bead is run.