Replacement windows for Christchurch homes

When replacing beats retrofitting

Retrofit is cheaper, so start there. Replacement makes more sense in four cases. The frame is rotten, corroded or twisted, so a sealed unit would be going into something that's failing anyway. The profile is too slim to hold a unit, which happens with some older aluminium joinery. The window leaks air around the sash badly enough that new glass wouldn't fix the draught. Or you want a different window: a bigger opening, a slider instead of a casement, a bifold onto the deck.

There's a fifth reason that's more about preference. If wet aluminium frames are what bothers you most, only a new frame with a thermal break, or a uPVC or timber one, fixes that. The aluminium double glazing page has the numbers.

An installer who does both should look at your frames and say which you need, window by window. Some houses end up mostly retrofit, with a couple of replacements where the weather's got in.

Consent and the Building Code for replacement windows

Building consent is usually not needed to replace windows in an existing house of up to two storeys. Schedule 1, exemption 8 of the Building Act covers work on windows and exterior doors, and MBIE's examples of exempt work include widening an opening with a new lintel and adding a window where there wasn't one. The exceptions are a window that failed within its required life (generally 15 years), work that affects a specified system such as sprinklers, or a building outside the exemption.

Being exempt doesn't mean anything goes. The work still has to meet the Building Code. Glass in doors, side panels, low panes, bathrooms and stairways has to be safety glass under NZS 4223.3, and a pane that wasn't safety glass before may need to be now. Fire rules apply within a metre of a boundary. And MBIE's guidance on insulation is that replacement joinery has to perform at least as well as what it replaces, without having to meet the full current standard for new builds.

Two more things to check. If your home is in a character area or heritage area, changing street-facing windows may need resource consent from the council, which is a planning matter separate from building consent. And official guidance doesn't say whether window replacement counts as restricted building work, so ask your installer whether a Licensed Building Practitioner will do or supervise the work.

What's included: architraves, sills and painting

Taking a window out disturbs everything around it: the gib and paint inside, the architraves, the sill, the flashings and cladding outside. Some installers quote the window and the fitting only. Others quote all-in, with the making good included. Published figures put the installer-only version 20 to 30% under the all-in one, and Christchurch homeowners asking online whether new architraves and painting were included have been surprised both ways.

So ask whether the old windows are removed and taken away, whether new architraves and sills are included, who repairs the gib and cladding, who paints, and whether GST is included. Then ask about timing: the deposit, the lead time for the joinery, and the days on site, which Consumer NZ puts at a couple of days for a replacement job.