Getting uPVC windows measured and ordered properly is the distinction in between a clean, leak-proof installation and a month of therapeutic sealant, packers, and arguments. I have actually surveyed homes from Walthamstow balconies to Hampstead villas, and the mistakes correspond: presuming openings are square, thinking sill angles, or copying old sizes without checking tolerances. This guide lays out how a London property owner or designer can determine with confidence, order from a relied on fabricator, and prevent the timeless pitfalls that cost windows and doors london Doorwins time and money.
Why measurement matters more in London real estate stock
London real estate is gloriously inconsistent. Victorian brickwork does not run real. Edwardian bays frequently belly in the middle, council stock from the 60s has deep exposes behind asbestos-impregnated mastic, and modern-day houses can have curtain walling tolerances that mask large deflections. On paper, a uPVC sash should drop into a rectangular opening with 10 mm clear each side. On site, that 10 mm can disappear quickly, especially where render beads, lumber liners, or twisted lintels pinch the aperture.
Add to that preservation restraints in Camden or Richmond, party wall considerations, and FENSA sign-off requirements for security glazing near doors and in low-level panes, and it ends up being clear why an intentional study saves worry. If you prepare to order direct from windows and doors suppliers in London, you require a survey standard that an expert fitter would stand behind.
What you are really measuring
When we talk about determining for uPVC windows and doors, there are 3 different frames in play:
- The brickwork opening, typically irregular, sometimes plastered, in some cases with a wood liner. The existing frame, which may include packers, silicone, or cover trims that conceal the true structure. The new frame being purchased, which the producer will size to your stated tight size or general size consisting of cill and add-ons.
Clarity on which of those you are measuring is important. Most double glazing providers in London expect you to offer the tight brick-to-brick opening size, and they will subtract an installation clearance, generally 10 mm in width and height. Some smaller custom window manufacturers in London will request the manufacturing size rather. Verify this before you touch a tape.
Tools that make a correct survey
A steel tape, a small spirit level, and a note pad still do the job, however a laser procedure speeds things up, specifically on tall sash replacements and wide aluminium bifold doors. A digital angle finder assists with splayed sills, common in bay windows throughout Haringey and Hackney. I likewise bring plastic shims to feel for pinches inside the reveal, and a square to examine head and cill are running true.
For apartment or condos, confirm access and internal finished flooring levels before measuring outdoor patio doors or moving doors. Terrace limits bring Approved Document M factors to consider into play, not just weathering and cill projection.
Step-by-step: determining a window opening properly
Start by eliminating as much trim as you can without damage. Surface-mounted architraves and quadrant beads conceal fact. Even if you prepare to re-trim, expose the structural opening to decrease guesswork.
Width precedes. Measure brick-to-brick on top, middle, and bottom, on the internal expose and again externally if accessible. Keep in mind the tiniest measurement. Do the exact same for height, measuring left, centre, and right. If height varies by more than 8 to 10 mm, anticipate to pack at the cill or change with an add-on.
Check diagonals. Run the tape corner to corner. If the diagonals differ by more than 10 to 12 mm on a normal casement, the opening runs out square. The frame can still be plumbed and levelled, but you need to permit adequate clearance to load correctly without forcing. I generally order 10 mm overall clearance on smaller windows. On big bays or composite assemblies, 12 to 15 mm can be more secure, especially in older brickwork.
Assess the cill. Numerous London homes have actually sloped masonry sills or wood sub-sills still in place. If the slope is aggressive, a basic 30 mm uPVC cill might rock. Record the angle, or a minimum of utilize a level to estimate fall. Keep in mind whether you will keep the existing stone sill. If fitting an external cill, define projection to suit the brick depth and any render. I like 85 to 150 mm depending on façade information, with end caps tucked under the cladding.
Look for blockages. Boiler flues, alarm cables, bell boxes, and steel balustrades typically crowd the frame. In Islington basement flats, I often find soil stacks tight to an expose. Procedure clear space for opening sashes, drip vents, and deal with swing.
Decide on sightlines. If you are changing lumber sashes with uPVC in conservation areas like Kensington and Chelsea, sightlines matter. Keep in mind the transom height of nearby windows so mullions align. For multi-part windows, verify equivalent or proportionate splits. Get this wrong and the elevation will look off even if the thermal performance is perfect.
Finally, record information points. Floors are seldom level. If a cill must align with a cooking area worktop or tiling course, note that height and concur the concern with your installer.
Ordering sizes vs manufacturing sizes
This is where numerous self-managed projects go wrong. There are three common conventions:
- Brick opening size with the supplier applying setup deductions. You supply 1200 mm by 1200 mm, the supplier manufactures at 1180 by 1180. Manufacturing size, no reductions. You supply 1180 by 1180 as the specific frame. Overall size consisting of external cill and add-ons. You include the cill projection or 20 mm frame extensions utilized to cover render.
Confirm with your selected London window and door company which convention they require. For the majority of domestic double glazing in London, I suggest providing brick opening sizes with a specific clearance requirement, then getting the provider's order verification that shows the production size. Cross-check that producing size against your notes before you sign off.
Glazing specification that matches London regs and comfort
Beyond size, a sound order consists of glass and thermal details that suit your home and the district's expectations.
I define low E glass, soft coat, on face 3 of the double-glazed unit as basic, with argon gas double glazing and a warm-edge spacer. For most uPVC windows London purchasers go for a whole-window U-value of 1.2 to 1.4 W/m ² K. If you care about energy efficient windows in London's environment and rising energy expenses, push for BFRC ranked glazing providers who can offer a Window Energy Ranking of A or above and test data for the specific system.
Trickle vents are still a frequent requirement depending on Part F. Where mechanical ventilation exists, you may omit vents, however this need to be warranted. On hectic roads in Lambeth or Hammersmith, acoustic glazing can be a lifesaver. A 6.4 mm acoustic laminate over 4 or 6 mm float, with uneven spacing, enhances dB reduction without huge cost. For safety zones near doors and low-level glazing, specify toughened or laminated to fulfill Part K. FENSA licensed window installers are utilized to collecting these information for their compliance certificates, however you need them right at order time with online or factory-direct suppliers.
For colour, bear in mind that foil surfaces add lead time. Popular choices include Anthracite Grey 7016, Chartwell Green, and smooth black on aluminium-look uPVC. If you are blending with aluminium windows and doors in other places in the property, align the RAL recommendations. On seaside or high-exposure websites along the Thames, verify hardware deterioration resistance. Stainless or coated hardware lasts longer than zinc-plated in London's damp city air.
Special cases: bays, bows, and lintel realities
Bay windows are their own discipline. Numerous London bays are lumber assemblies that function as assistance for the roof canopy or first-floor bay. Do not remove a structural post without temporary propping and a prepare for steel or wood posts incorporated into the new frames. When measuring, get each element width, the angles in between facets, and the wall-to-frame returns. Fabricators can provide bay poles and load-bearing jacks, however they require exact information. I picture and sketch every bay with dimensions.
For bow windows, where a curved look is developed from faceted frames, the projection matters. Choose if you are matching the existing bow tie detail and roof, or flattening to a straight frame. Planning in districts like Westminster will care.
Lintels are the elephant in the room. Numerous older setups use the wood frame itself as the assistance for the masonry above. When that timber is eliminated, the brickwork can drop or break. If there is no noticeable lintel, get a home builder or structural engineer to validate. It is poor practice to rely on uPVC frames for load. You can still proceed, however element lintel setup into your budget and programme.
Choosing between uPVC and aluminium when sightlines matter
Even though this short article focuses on uPVC, I often compare thermally broken aluminium windows when clients want slimmer sightlines or bigger periods. For instance, aluminium bifold doors in London homes deal with large openings with less frame bulk and much better rigidity than uPVC. Thermally broken aluminium windows now publish whole-window U-values near 1.2 to 1.4 with the best glass, that makes the energy effectiveness in windows and doors discussion more nuanced.
If you mix materials, decide frame depths and colour finishes in advance. A common uPVC frame might be 70 mm deep. Aluminium systems differ from 60 to 75 mm. Lining up these avoids uncomfortable internal plaster returns. In period homes where deep reveals assistance, uPVC often sits nicely. In modern flats with shallow openings, aluminium's minimized depth can save a headache.
The provider landscape and what to look for
There are numerous double glazing providers London house owners can approach directly. A few practical checks assist separate marketing gloss from dependable output:
- Ask for BFRC certificates for their typical double glazed units and the particular profile system. Rehau, Liniar, Deceuninck, Kommerling, and Veka are common uPVC systems in the UK market and carry out well when made correctly. Confirm whether they are FENSA signed up or work with Certass authorized double glazing installers for fitting. Even if you are supply only, it is telling if a provider routinely feeds licensed teams. Inspect corner weld quality, gasket seating, and reinforcement practice. On tall sashes I expect steel reinforcement as per the system manual. For coloured foils, ask about substrate colour. A brown or anthracite base hides scratches much better than white when foiled. Lead times and service windows matter. A made to measure windows London supplier with 5 to 10 working day lead times for white, and 3 to 5 weeks for foils, is common. Anything significantly much shorter may be a warning for hurried QC.
I keep a list of trusted glazing professionals London architects like to use for consistent ending up. Good doors and windows suppliers will also happily supply glazing beads and extra gaskets for site insurance coverage. If the discussion feels protective when you ask technical questions, relocation on.
Ordering information that keep installers happy
The devil is in the notes. Beyond sizes and glass specification, include hinge side for each sash, deal with colour, drip vent colour, cill type and forecast, packer and add-on requirements, and any astragal bar or Georgian bar layouts. On French doors London jobs, confirm master leaf, opening instructions, and limit type. If accessibility is a concern, define a low threshold with suitable drainage and weather rating.
For patio doors London apartments, confirm whether the track can sit flush with the ended up floor or needs an upstand. With moving doors London providers, choose between inline sliders and lift-and-slide. The latter offers smoother action on much heavier panes however includes expense and frame depth.
Security spec must reference PAS 24 if you desire new-build level defense. On front doors and back entrances London house owners anticipate multi-point locks as basic, but the cylinder grade matters. SS312 Diamond or at least TS007 3-star cylinders resist snapping. If you are connecting into an alarm system, request magnetic contact preparation during fabrication.
Making buddies with structure control, FENSA, and paperwork
If you utilize FENSA certified window installers, they will self-certify compliance with Structure Regulations and issue a certificate for conveyancing. If you are doing supply just and self-fitting, or using a non-registered trimmer, you will need to inform building control or use Certass where applicable. This impacts insurance and resale. I have actually seen sales fail in Barnet over missing out on certificates for a couple of replacement casements.
Part L for energy, Part F for ventilation, Part K for safety glazing, Part B for ways of escape, and Part M for ease of access around doors are the primary files you will touch. Means of escape windows require minimum clear openings, generally 0.33 m ² with a minimum measurement of 450 mm. That has style ramifications for sash sizes and egress hinges in bed rooms. Discuss this early, particularly in loft conversions in Enfield or Croydon.
Tolerances, packers, and how to avoid call-backs
Even the best study finds surprises. I permit adjustable packers, a number of 20 mm add-ons, and spare trims on every task. You can mask a 5 mm plaster wave with a neat trim, however you can not make a too-large frame smaller sized without cutting and jeopardizing the support. Err towards a touch smaller, never larger.
When frames arrive, measure them before you rip out the old ones. I examine the manufacturing labels against my order confirmation. If sizes are wrong, you can still keep your house protected while the supplier remakes the systems. On site, use solid packers at fixing points, not wedges of timber, and avoid overpacking the head which can bow the frame and trigger sash binding.
Sealant option matters. In London's mixed brick and stone façades, neutral cure silicone or hybrid polymer mastics adhere better and resist staining compared to acetoxy silicone. On listed exteriors, speak with conservation officers before using wide external trims.
Pricing realism and where to save
Supply only uPVC casements in white, double glazed, with low E and argon, normally cost in between ₤ 250 and ₤ 450 per average window, depending upon size and specification. Coloured foils, laminated acoustic glass, and intricate layouts push that up. Aluminium windows and doors, specifically custom aluminium doors London clients enjoy for slender sightlines, command a premium, frequently 2 to 3 times uPVC for the exact same opening.
Where to economise without regret: keep to standard colours, prevent over-specified bars, and rationalize opening lights. Where not to skimp: glass spec, hardware, and supplier quality control. A stopped working sealed system or a floppy hinge expenses more in disruption than the saving ever did.
Sustainability and lifecycle thinking
Sustainable glazing London jobs now inquire about recyclability and embodied carbon. uPVC is recyclable, and significant systems houses run take-back schemes. Ask your provider how offcuts and old frames are dealt with. Specify warm-edge spacers and greater gas fill with robust seals for long-term efficiency. Consider laminated glass with a solar control layer on south-facing elevations to manage getting too hot in more recent airtight builds.
BFRC rated glazing providers can show you energy balance figures, not simply U-values, so you can tune solar gain and heat loss for each elevation. In dense areas like Southwark where summertime heat build-up is real, this information pays off.
A useful determining list you can trust
- Confirm whether your provider wants brick opening sizes or producing sizes, and what deduction they will apply. Measure width and height in three locations each, take the tiniest, and examine diagonals for squareness. Record cill conditions, slopes, and needed forecast, along with any need for add-ons to cover render. Specify glass: low E, argon, warm-edge spacer, security glazing where needed, and acoustic where needed. Note hinge sides, opening instructions, vents, handle surfaces, bars, and any compliance requirements like egress hinges.
When to call an expert surveyor
There is no pity in asking a pro to verify sizes, particularly for bays, structural openings, or large mixes with sidelights and fanlights. Double glazing business London based property surveyors understand the borough peculiarities and can identify missing out on lintels and covert services. If you are buying aluminium doors London style sliding or bifold systems with tight tolerances, a professional website study can be affordable insurance.
For business glazing suppliers London tasks, tenders will typically mandate an approved survey anyway. On residential double glazing London supply-only jobs, it is still your finest course to a novice fit.
Bringing all of it together
Correctly determined and specified uPVC doors and windows provide quiet, warm rooms and a clean façade line. The procedure rewards care: understand the opening, pick a spec that addresses London's guidelines and noise, and order through relied on double glazing suppliers who provide clear documents and consistent fabrication. Whether you are changing exhausted casements in a Lewisham semi, updating to energy efficient windows London flat by flat in a block, or mixing uPVC with aluminium doors and windows in a mixed-material restoration, the very same fundamentals apply.
A final suggestion from years on the tools: photograph every opening with a tape reading visible, and conserve those images with the room name. When the delivery shows up or a question originates from the factory, those images cut through doubt. It is basic paperwork that secures you, your installer, and your budget.
If you keep the measurements honest, the specifications recorded, and the providers liable, your new windows will look right, perform well, and sail through FENSA or Certass paperwork. That is how a London task avoids snag lists and lives gladly with its brand-new glazing for decades.
Doorwins
Address: Office 11, Dearden House, W Gate, London W5 1BS
Phone: 020 8629 1250
Our specialists at Doorwins are among the leading aluminium glazing companies in London. Our company supply and professionally fit roof lanterns and sliding doors for modern homes and luxury developments.
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uPVC & Aluminium Styles: uPVC casement windows; uPVC bifold doors; roof lanterns. Aluminium thermally-broken windows; aluminium bifold doors; roof walk-on glass. As a London double glazing company, we provide bespoke fabrication and fitting for residential and commercial projects, covering replacement windows, new-builds, extensions, and refurbishments.
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