Illustration of a brick house with white windows and a green front door with one pull handle

Advice & Guides

The Cii Double Glazing Blog

Practical guides to choosing windows, doors and roof glazing, planning upgrades and understanding repairs.

Two pairs of white uPVC French doors on the rendered rear wall of a house in Chelmsford, one pair with glazed side panels, installed by Cii Double Glazing

Door Guides8 November 2026

Patio Doors: Choosing French, Sliding or Bi-fold for Your Opening

Compare French, sliding and bi-fold patio doors for your opening: swing and stacking room, clear walk-through, glazing and what an itemised quote should list.

Lower half of a closed cream uPVC flush casement window with flat-faced frames above a weathered stone sill on a pale rendered wall, with lavender in front

Window Guides28 October 2026

Flush Sash Windows vs Sliding Sash: Which Suits Your Home?

Flush sash vs sliding sash windows: how each opens, looks and cleans, which suits a period frontage, and what to compare for the same opening at survey.

Red brick house at dusk on a frosty evening, its white uPVC double glazed windows lit warmly from inside, with frost on the front lawn and hedge

Window Guides27 October 2026

Benefit of Double Glazed Windows: A Homeowner's Guide

What double glazed windows change at home: warmer rooms, less street noise and less condensation, and when a repair makes more sense than a new window.

Chrome locking handle on the bottom rail of a closed anthracite grey uPVC casement window, seen from inside with rain on the glass and a garden fence beyond

Repair Guides26 October 2026

Fix Double Glazing Window Handle: Repair or Replace?

Window handle stiff, loose or spinning? Find out whether the handle, the locking gearbox or the hinges are at fault, and when a repair beats a new window.

White uPVC casement window seen from inside a living room, with fog trapped between the panes of the left sealed unit and a clear view of the garden through the right pane

Repair Guides23 October 2026

Misted Double Glazing: Repair or Replace the Unit?

Misted double glazing? Find out where the moisture sits, when a new sealed unit in the existing frame is enough and when the whole window needs replacing.

Pair of cream French doors with fixed side panels set in the yellow stock brick rear wall of a terraced house, under a concrete lintel, with a slate step, a slot drain and a dining room beyond

Door Guides22 October 2026

Replacing a Window with French Doors: What Needs Checking First?

Turning a window into French doors? Check the lintel, the wall below the sill, the threshold, drainage and approvals before you ask for an itemised quote.

View looking up through a single-panel flat rooflight with a slim anthracite frame and a deep white plastered reveal in a kitchen extension ceiling, pale blue sky and a bare branch beyond

Roof Glazing Guides21 October 2026

Triple Glazed Flat Roof Lights: Choice and Installation

Compare triple and double glazed flat rooflights, fixed and opening units and the kerb detail, then see what an itemised written quote after survey should list.

Low close-up of an anthracite grey aluminium sliding patio door, part open, with a low twin-track threshold, drainage slots and a slot drain in wet grey patio paving

Door Guides20 October 2026

Sliding Patio Door Installation: Thresholds, Drainage and Everyday Access

Plan sliding patio door installation around the clear opening, threshold height and track drainage, then know what to agree at survey and test at handover.

Rear elevation of a red brick semi-detached house with matching anthracite grey windows and a sliding patio door, the neighbouring half keeping white frames

Planning Guides18 October 2026

Doors and Windows Installation: Plan One Fitting Project

Plan doors and windows installation as one project: list every opening, match finishes across each elevation, set the fitting order and agree who finishes.

Newly fitted white uPVC French doors and a casement window in a kitchen-diner, with dust sheets, a spirit level and a sealant gun on the floor

Planning Guides17 October 2026

Door and Window Installation: 7 Big Mistakes to Avoid

Seven door and window installation mistakes to avoid, from rough measurements and unclear quotes to fitting day access, sealing and the final handover checks.

Anthracite grey uPVC casement bay window with angled side returns, a lead-covered bay roof and a stone sill on a red brick terraced house

Window Guides16 October 2026

Bay Window Double Glazing: Survey and Replacement Guide

How to replace a bay window with double glazing: keep its shape and sightlines, check the support and bay roof, know when permission applies and what to agree.

White uPVC bedroom window seen from inside, with a fixed pane, an opening sash swung inwards and a trickle vent along the frame head, gardens beyond

Planning Guides15 October 2026

Replacement Window Building Regulations in England: A Homeowner's Checklist

A checklist for replacement window building regulations in England: planning, heat loss, ventilation, safety glass, escape openings and who certifies the work.

White double glazed sliding sash window with a two-over-two pane layout set back in the brick reveal of a yellow brick terraced house

Window Guides14 October 2026

Sash Window Installation: Double Glazing That Fits

How to replace sash windows with double glazing and keep their character: what to record, which details to agree, permission checks and what fitting involves.

Old white-painted timber bay window seen from inside a living room, with a survey folder, pencil and tape measure on the window board

Planning Guides13 October 2026

What Happens at a Window and Door Replacement Survey?

What a window and door replacement survey covers: how to prepare, what the surveyor checks at each opening, and what the written quote should then include.

An anthracite grey composite front door beside a white half-glazed uPVC front door on a pair of pebble-dashed semi-detached houses

Door Guides10 October 2026

Composite vs uPVC Front Doors: Which Fits Your Home?

Composite vs uPVC front doors compared on looks, glazing, security, thermal performance and fitting, plus the questions to ask at your home survey in Essex.

Replacement friction hinges, a window handle, rubber gasket and a screwdriver on the window board in front of a white uPVC casement window

Repair Guides9 October 2026

Double Glazing Repair: 7 Fixes Before Full Replacement

Seven double glazing repairs to check before you replace a window or door: misted units, cracked glass, handles, hinges, seals, door locks and patio rollers.

Window Guides8 October 2026

Double Glazed Windows: uPVC vs Aluminium Quotes

Compare uPVC and aluminium window quotes like for like: sizes, opening layout, glass, whole-window U-value and fitting, and when a new sealed unit is enough.

Illustration of an anthracite hipped roof lantern on the flat roof of a brick extension

Roof Glazing Guides7 October 2026

Roof Lanterns for Extensions: What to Plan First

Plan roof lanterns for a flat-roof extension: compare lower-profile rooflights, size the opening, choose glazing and coordinate fitting and approvals.

Illustrated comparison of open aluminium bi-fold doors on the left and sliding patio doors on the right

Door Guides6 October 2026

Bi-fold vs Sliding Doors for an Extension

Compare bi-fold and sliding doors for your extension: clear opening space, garden views, everyday access, thresholds and the questions to ask at a survey.