Metal roofing in The Blue Mountains

Ice dams form because snow sits on a roof long enough to melt from underneath, run down to the cold eave, and refreeze. Everything that reduces how long snow sits there reduces the problem. A steep pitch helps. A slick, continuous metal surface helps enormously. Put them together, which is what a Blue Mountains chalet with a standing-seam roof is, and the snow generally leaves before the cycle can establish.

That is why metal is more common here than anywhere else in the region, and why the owners who have it tend to be emphatic about it. It is not only durability. It is not spending every February watching ice build over the entry and wondering what it is doing to the ceiling.

It also removes the load question. A metre of wet snow on a roof is a serious weight, and while properly built roofs are designed for it, not accumulating it in the first place is a straightforwardly better position to be in on the heaviest-snowfall roofs in the region.

The corollary of a roof that sheds well is that everything below it is in the firing line. On a steep chalet roof, a slab of accumulated snow releasing at once carries real force, and entries, decks, hot tubs, gas meters and parked cars are all things it can reach.

Snow guards are what make a metal roof civilised. They do not hold the snow indefinitely; they break the sheet up so it comes off in manageable amounts rather than as a single mass. Placement is the skilled part: above entries and walkways, over anything vulnerable, and in a pattern matched to the panel and the pitch rather than scattered.

We plan this at quote stage rather than treating it as an accessory. A metal roof designed without thinking about where the snow lands is a roof that will eventually damage something below it.

Many chalets have cathedral ceilings, and a metal roof over an unventilated cathedral assembly can trap moisture against the deck. Metal is impermeable, so any water vapour reaching the underside of the sheathing has nowhere to go. If the rafter bays have no continuous air path, that moisture condenses and the deck suffers, quietly, for years.

The correct approach on these roofs is either to establish a proper vented path in every rafter bay from soffit to ridge, or to build a vented over-roof above the existing assembly and lay the metal on that. Which one is right depends on what we find when the old covering comes off.

This is the part of a chalet metal roof that separates a job done properly from one that looks identical on completion and causes trouble in a decade. It is worth asking about specifically, whoever you have quote the work.