Exterior Caulking near you

Every gap on the outside of a house is not a defect. Weep holes in the bottom course of a cavity wall and above openings are there so that water reaching a cavity tray can drain back out; ventilation slots in a soffit or an over-fascia vent are feeding the roof void; a gap at the bottom of a cladding cavity is the drainage and ventilation path the system depends on; and airbricks are ventilating a suspended timber floor.

Approved Document C puts a number on that last one. For a suspended timber ground floor, and again for a suspended concrete floor, it calls for a ventilated air space with ventilation openings placed in two opposing external walls so that ventilating air has a free path between opposite sides and to all parts of the floor void, with openings of not less than either 1500 square millimetres per metre run of external wall or 500 square millimetres per square metre of floor area, whichever gives the greater opening area, and pipes carrying ventilating air of at least 100 millimetres diameter. The openings are to have grilles that keep vermin out of the sub-floor without unduly resisting the airflow.

Seal those up — with mastic, with expanding foam, with render, or by raising a patio or a decking across them — and the sub-floor stops drying. The consequences are damp, decaying floor timbers and a smell in the ground floor rooms, and they arrive a year or two after the work, which is why the connection is so rarely made. Any exterior sealing job should begin by identifying what every opening on the elevation is for.

A joint that has been re-sealed three times and still leaks is telling you about the detail behind it. The usual causes are a cill with no fall, or with a drip on the underside that has been filled by successive coats of paint, so water tracks back along the soffit of the cill and into the wall; a frame set too far forward in the reveal on a wall taking severe driving rain; a missing or bridged damp-proof course or cavity tray above an opening; or a cavity closer that was never properly formed. Approved Document C expects damp-proof courses to be provided to direct moisture outwards where the downward flow would be interrupted at an obstruction such as some types of lintel, where cills and their joints do not form a complete barrier, and where reveal elements and their joints do not form a complete barrier at openings.

Geometry does the rest. A bead that is deep and narrow, or one that has bonded to the back of the joint as well as to both faces, cannot deform when the joint moves and tears instead. A bead laid over a joint rather than in it has almost no thickness at the edges where the stress is highest. And a bead that was applied in cold weather is being compressed every summer and one applied in a heatwave is being stretched every winter, which is why movement joints are sized rather than guessed at.

The third category is substrate. Sealant will not bond to dust, to a friable render face, to damp masonry, or to old silicone, and on some porous stone an unsuitable sealant leaves a permanent oily halo either side of the bead. Where a bead has failed cleanly off one face and stayed stuck to the other, that is an adhesion failure and the answer is preparation and primer, not a different cartridge.

Sealing is priced on removal, access and preparation rather than on metres of bead. The variables are how many joints there are and how long they are, what has to be cut out first and how well the old material is stuck, the height and how each elevation will be reached safely, the substrate and whether it needs priming or masking, whether backer rod and correctly sized movement joints are involved, the sealant specified, and whether a defect behind the joint has to be put right before anything is sealed. A ground-floor window is a different job from the same window three storeys up over a conservatory roof.

This is the kind of small, specific job LokalMatch exists for. Photograph the joints, describe where they are and what has already been tried, add your postcode, and firms covering your area come back to you directly. Using LokalMatch costs homeowners nothing; pros pay for the requests they receive. LokalMatch does not do the sealing, does not set prices and does not vet, rank or recommend anybody, so making sure whoever comes knows the difference between a joint and a drainage opening is a check that stays with you.