Local chimney waterproofing for Middleburg homes

Silanes on dense surfaces

Of the clear repellents, silanes have the smallest molecules. BIA's note explains that the small size helps them get into dense materials, and that they are supplied at high concentrations of active ingredient. The reaction that makes them water-repellent goes fastest on alkaline surfaces like concrete and concrete block, which act as their own catalyst.

On less alkaline clay brick, some products carry an added catalyst to help. Where a chimney has a very dense brick, a block section, or a concrete element that needs treatment, a silane or a blend led by silane may suit it better, and we explain the choice made.

Waiting after the joints are repointed

New mortar in a joint is still hardening and still giving off water for days after it is placed. Coating it too soon can interfere with that cure and lock the moisture in. BIA's pre-coating checklist sets a floor of 72 hours for freshly repointed mortar and repaired sealant joints, and the maker of the repellent we use sets the same interval after tuckpointing or other repairs.

On a chimney that has just been repointed, treatment is therefore booked as a separate visit. Writing the cure period on the estimate keeps anyone from spraying on the same afternoon the trowels are put away.

Protecting windows, skylights and shingles

Silane and siloxane products react with unprotected glass as well as brick, as BIA's note points out, and the note adds that these chemicals can etch glass. The maker of the product we apply adds paint, plants and asphalt-based materials such as roof shingles to the list of things to keep clear. So before any spraying, the glass in windows, skylights and doors close to the stack is covered, the roof surface around it is shielded, and plants below are protected as the directions describe. Any overspray that reaches an uncovered surface is washed off with soap and water straight away.