Standard or custom windows: What suits your project?
Window planning for new builds and existing homes
The window opening is in place, the floor plan is almost settled – yet the choice between a standard and custom window remains open. This is the point to compare more than an apparently suitable width. Clear structural opening dimensions, the intended installation detail, opening direction, room use and the appearance of the whole façade all matter. A standard size can simplify planning when the openings and required function genuinely suit it. A custom window is often the cleaner answer where an existing building has uneven reveals, particular alignment lines or a deliberately planned window division. Coordinating the complete project before selecting dimensions avoids compromises that later show in daylight, furnishing, installation or elevation.
The installation situation matters, not the catalogue size
A window dimension does not automatically describe the opening in the wall. Several layers sit between the structural opening, outside frame size, possible installation clearance and the visible glazed area. In a new build, the opening can be designed around the chosen window system. In an existing building, the sequence is usually reversed: record the existing openings accurately, then decide whether an available format fits without design or technical drawbacks. Take several measurements at every opening. Width and height can differ at the top, centre and bottom; reveal depth, lintel, sill and orientation also belong in the survey. One measurement at the narrowest or widest point is not enough for an order.
Create a clear dimension chain for every position: existing wall opening, planned perimeter joint, outside frame size and anticipated clear glazed area. Ask the responsible trade professional to explain which reference edges the quote and order dimensions use. This prevents, for example, a finished plaster dimension being confused with a structural-opening dimension. Do not average measurements from several similar openings; a small variation can be decisive at one location. Then compare standard and custom solutions on the same drawing. Only then can you see whether a standard format merely fits mathematically or whether reveal widths, sill, installation detail and visible proportions also work together. Keep unresolved dimensions as checks on the window schedule rather than treating them as assumptions in the order.
Standard sizes: useful for repetition and clear planning
Standard windows are not a judgement on quality; they are a planning strategy. They suit repeating window lines, openings that can still be adjusted and a window type intended to work in several rooms. This can be useful for an extension with similar ancillary rooms or a new build with a regular façade grid. Fewer variants make it easier to compare elevations and coordinate details such as sill heights, shutters, sun control or window boards. However, do not select a standard format simply because it appears available on paper. If it requires disproportionate alteration of the opening or loses a sensible sash arrangement, the simplification is only apparent.
A standard format deserves a reality check before ordering: does it fit each opening with the intended installation detail? Do the windows sit at convincing heights across the façade? Is there enough room inside for the sash? And does the glazed proportion remain appropriate in rooms of different sizes? For a calm, unified elevation, a fixed-glazed window beside an opening window can be a suitable addition. It serves a different purpose, however: it does not provide its own ventilation opening. Do not plan on the principle that every panel must match; decide which panel provides light, which ventilates and which is intended for everyday operation.
Keep the whole project in view
Custom windows: when the building sets the dimensions
Custom windows are especially helpful where the wall opening, façade composition or room requires a particular dimension. Typical examples include renovations with differently sized openings, alterations, narrow wall sections, tall rooms or windows intended to align with existing doors and cornices. A defined size also gives greater design freedom where windows are to align precisely beside or above one another. Made to measure does not mean treating every opening as an isolated case without a system. It is often more convincing to develop several deliberately defined sizes and repeat them where the architecture allows. This keeps the façade ordered without forcing identical structural openings.
The question is not “Is a special size better?” but “Which size solves the task without compensating tricks?” A window that is too small can create wide junction zones or awkward reveals; one that is too large can require disproportionate intervention in the wall and installation detail. Draw the outside frame edge, visible frame and glazed area on an elevation. Only then can you tell whether a grid really works. In an older building, an outward-opening historic-style “Kombi” casement window may be relevant as a design idea if its intended division suits the façade. The product name does not establish which dimensions or fittings are available for your order; these must be checked for the specific configuration.
Read the façade as a whole first
Windows do not work in isolation. What matters is the relationship of window to wall area, window to window and window to door. Start with a complete elevation of every façade. Mark alignment lines, storey heights, sill heights, lintels and adjoining elements. Then assess which lines should continue deliberately and where an offset has an architectural reason. During a renovation, an identical window width can look wrong in two places if the existing wall sections differ in width. Conversely, a different dimension need not be disruptive if it responds to a doorway or expresses a clear room function. An elevation drawing protects against choices that seem plausible from inside but appear accidental from outside.
Window division also changes its effect. A double-sash window can create a balanced view in a wider opening, while one broad sash may need more clearance inside. An inward-opening double-sash window is therefore not simply the larger version of a single-sash window, but a different proposal for operation and appearance. Check the mullion position, sash widths and the position of open sashes on the plan. Assess glazing bars only after proportions and sash division are settled. Decorative bars and bars that divide the glass represent different design approaches; establish which version is available and appropriate through the specific design.
Room function also determines the opening type
A window can provide a view, daylight, rapid ventilation, help with cleaning a room or accompany access outdoors. These tasks do not always require the same opening type. In an area ventilated regularly, the sash must be easy to reach and must not clash with furniture, fittings or curtains. A sash swinging far into a workspace can be inconvenient, while in a recess it may cause no problem. Discuss cleaning of externally accessible or difficult-to-reach panes early as well. Size directly affects these practical questions because larger sashes need more opening space and can feel different to operate.
Review the floor plan with opening arcs drawn in. For inward-opening windows, radiators, curtains, kitchen worktops and furniture are important discussion points. Outward-opening versions move the opening zone outdoors, affecting exterior space and their position near paths or decks. An inward-opening single-sash window can be a straightforward solution for a modest opening if the room permits the swing area. Test critical situations on the plan with an open cupboard door, a pulled-out chair or planned tapware. This reveals whether a format that works on paper will remain comfortable in everyday use. Also ask for confirmation of available dimensions, handing, opening direction and the operating arrangement intended for your project before finalising window sizes.
Assess glazed area, division and outlook separately
A larger outside dimension does not automatically create a proportionally larger outlook. Frame width, sash division, mullions and glazing bars shape the visible glazed area. Anyone seeking better daylight and connection to the view should compare the clear glazed area on the drawing, not only the frame edge. Two windows of the same width can feel very different where one combines a fixed panel with an opening panel and the other is divided centrally. Height matters too: a taller window can visually lengthen a room, but it changes the sill, furnishing and view outside. A low connection to the garden raises different questions from a window above a work surface.
A useful approach is to note one priority for each room: light, outlook, ventilation, privacy or façade rhythm. This often leads to a mix of window types rather than one format throughout the house. Where daylight and a framed view are the priority, a fixed element can be effective; where ventilation comes first, an operable panel is needed. For a high wall zone, an top-hung outward-opening awning window can be a functional alternative if reach and installation circumstances are planned. It does not automatically replace a window needed for eye-level views or greater ventilation.
Keep the whole project in view
Special shapes need a stronger design rationale
Angled, triangular, round or semi-round windows are often seen as individual solutions. They can respond convincingly to a roof form, gable or unusual room geometry. For that reason, they should not arise as leftover dimensions after rectangular formats have been fixed. First ask which line the building form establishes and whether the special shape makes sense inside as well as out. A triangular element below a roof slope can create a clear connection to the structure; without that relationship it can make the façade restless. Special shapes also organise glass, frames and adjoining insulation or cladding differently from a rectangle.
With a fixed-glazed triangular or angled window the fixed glazing is already stated in the product name. This can suit a location where light and form matter more than operation at that point. Plan ventilation for the entire room elsewhere. Always draw the internal elevation for special shapes: it shows whether the form achieves the intended effect or competes with cupboards, roof slopes and lighting. Before ordering, also establish the dimension limits, divisions and installation details offered for the required version. A special shape should not only impress on the external elevation but also have a clearly solvable role within the room.
In existing buildings, surveying is a project phase in its own right
Window openings in existing buildings are rarely perfectly alike. Plaster layers, linings, earlier alterations and reveals that are slightly out of plumb can affect the survey. Record every opening individually and clearly: width and height at several points, reveal depth, sill, lintel, existing window board and obstacles inside and out. Dimensioned photographs and an elevation sketch help prevent mix-ups. Also note the intended installation plane. For an opening in a roof, roof pitch, internal lining, accessible operating height and the correct roof face must also be documented clearly. A roof pivot window is its own configuration, not simply a vertical standard window installed elsewhere. The project-specific survey and installation design must therefore suit the roof construction.
If openings are to be enlarged, reduced or combined, this is not solely a window question. Qualified design and construction professionals should assess effects on the existing wall, lintel, façade and internal fit-out. In New Zealand, a building-consent exemption does not remove Building Code duties, and district-plan controls can still require resource consent. Check the property, scope of alteration, heritage status, foundations, services, boundary fire separation and stormwater requirements with the relevant council before ordering windows or altering openings. A custom window may sometimes avoid building alterations, but it does not replace project-specific checks where the wall opening itself is changed.
Set door and window dimensions together
Patio, balcony and sliding doors often influence the window grid more than the other way around. Their height, threshold, handle side and opening movement determine adjacent window alignments and use of the outdoor area. Where a large garden opening is planned, decide early whether a hinged, folding or sliding solution better supports everyday life. Side window panels and elements above can then be related to it cleanly. Standardising a window format simply because it sits beside a door can produce an unsuitable sill level or an unsettled façade line. Conversely, a continuous height across doors and windows can create strong order when it suits both the room and external elevation.
With a Patio Life lift-and-slide door the large opening itself is the starting point for planning adjacent panels. Check on the floor plan where fixed furniture, circulation routes and the desired deck area will sit. On the elevation, compare the head height, side wall areas and visual weight against smaller windows. Ask about possible dimensions, sash division, required junctions and the intended threshold build-up for the exact configuration. This clarifies whether neighbouring windows should align exactly, be deliberately offset or be planned as fixed side panels. Standard and custom choices can differ for doors and windows; what matters is that both form a coherent ensemble.
From sketch to an order-ready window schedule
A reliable window schedule combines design with unambiguous information. For each position, record the room and façade reference, structural-opening dimensions, required outside frame dimensions, opening type, handing, number of sashes, divisions, fixed panels and particular operating notes. Add the required position in the wall and identify dimensions still needing site verification. A position number should match on the floor plan, elevation and schedule. With similar windows, this prevents right- and left-hand elements being swapped or a special division being assigned to the wrong room. Keep open matters visible rather than presenting assumptions as final specifications.
Before ordering, compare the survey, elevation and quotation together. In particular, check that every window size belongs to the correct opening, opening directions make sense on the plan and fixed panels are truly where required. Also ask for the confirmed delivery date: Bloomcabin has a delivery time of 4–6 weeks, subject to order confirmation. Windows and doors have a 5-year guarantee. Place the order only after dimensions and specification have been fully checked; a timing assumption does not replace a confirmed order. This turns the choice between standard and custom from a matter of instinct into a traceable specification for the whole project.
Frequently asked questions
Are standard windows always cheaper than custom windows?
This cannot be answered in general terms. Overall cost depends not only on the window, but also on opening alterations, installation details, façade work and the number of different positions. Compare complete, like-for-like configurations and consider whether an apparently suitable standard size triggers additional building work.
How do I measure an existing window opening correctly?
Measure width and height in several places and record the smallest or otherwise relevant values clearly. Add reveal depth, sill, lintel, window board and features such as out-of-square openings. Set the final order dimension only after consulting the professionals responsible for surveying and installation.
Can I combine different window sizes on one façade?
Yes, if the differences follow an identifiable order. Deliberately align head heights, sills, axes or window divisions, for example. Different sizes can express different room functions. Always prepare a complete façade elevation, because windows that suit individual rooms may look unbalanced from outside.
When is a fixed window a good choice?
A fixed window suits a place where light, outlook or a clear panel division is wanted and ventilation is provided elsewhere. It is not a universal answer for large openings. Check ventilation needs for the whole room, cleaning access and the desired operation before replacing an opening panel.
What should I have confirmed before ordering?
Confirm dimensions, opening direction, handing, sash and panel division, wall position and all relevant installation details. Compare the quotation, survey, floor plan and façade elevation position by position. Where existing wall openings are changed, the responsible design and construction professionals should check feasibility in advance.
Next step
Standard windows are a good choice where a repeating grid and appropriately planned openings support the project. Custom windows are strong where existing conditions, proportions or use require an exact format. Both approaches produce convincing results only when external elevation, internal space and installation are considered together. Start with a careful survey and façade drawing, define the function of every panel and transfer the decisions into a clear window schedule. This way, you choose not simply an available size but a window that suits the opening, room and building.
