Did you know that incorrect measurements account for over 40% of internal bifold doors installation problems in UK homes? A simple 10mm measuring error can cost homeowners hundreds of pounds in replacements. It's frustrating and completely avoidable.
Getting accurate measurements for internal bifold doors UK installations isn't just about using a tape measure correctly. The critical 10-12mm fitting tolerance can make or break your project. Many DIY enthusiasts overlook this crucial detail. Professional installers know that proper measuring techniques save time, money, and headaches.
In this comprehensive guide, you'll learn the exact three-point measuring method used by professionals. We'll cover essential tools, step-by-step instructions, and common pitfalls to avoid. Whether you're installing wooden doors or modern internal aluminium bifold doors, this guide ensures you get perfect measurements first time. You'll discover standard UK sizes, special considerations for different rooms, and when custom sizing becomes necessary.
Understanding Internal Bifold Doors Before Measuring
Before grabbing your tape measure, let's understand what you're measuring. Internal bifold doors come in various configurations. Knowing these basics prevents costly ordering mistakes.
Types and Configurations
Single bifold doors feature two panels that fold together. Double bifold doors use four panels. Simple enough, right?
Configuration codes tell you how panels operate. You'll see notations like:
2+0 - Two panels folding one direction
3+1 - Three folding panels plus one traffic door
3+3 - Three panels fold left, three fold right
The traffic door (or lead door) opens independently. It contains the multi-point locking system. Perfect for quick access without folding all panels back.
Panel Width Guidelines:
| Configuration Type | Minimum Width | Maximum Width | Standard Range |
| Odd panels | 400mm | 1200mm | 400-900mm |
| Even panels | 700mm | 1200mm | 400-900mm |
Most internal bifold doors UK installations use panels between 600-800mm. This range balances functionality with smooth operation.
Nominal vs Actual Sizes
Here's where many DIYers get confused. Manufacturers list nominal sizes, not actual measurements.
Actual size = What you physically measureNominal size = The rounded number on the label
They typically differ by 12mm. An actual door measuring 606mm wide gets labeled as 610mm nominal. Height follows the same principle.
This matters when ordering internal aluminium bifold doors. You need actual measurements for proper fitting. The nominal size is just for classification. Always clarify which measurement the supplier needs.
Essential Tools and Preparation
Getting the right measurements starts with proper tools and setup. You don't need expensive equipment. Just the basics done right.
Required Tools
Here's what you'll need:
| Tool | Purpose | Why It's Essential |
| Tape measure (3m minimum) | Width and height measurements | Metal ones stay straight for accuracy |
| Large spirit level | Check if opening is square | Prevents fitting problems later |
| Paper and pencil | Record measurements | Digital notes work too |
| Step ladder | Reach top measurements safely | Don't guess heights |
| Helper | Hold tape for large openings | Makes measuring easier and accurate |
That spirit level? It's crucial for internal bifold doors. Uneven openings cause endless problems.
Pre-Measurement Steps
First, remove existing doors completely. You need clear access to the frame edges. Hinges and handles get in the way.
Clear the entire doorway area. Move furniture back at least one meter. You'll need space to work comfortably.
Check where panels will fold. Do they have room to stack? Internal bifold doors UK installations often fail because nobody checked this first.
For expensive projects or internal aluminium bifold doors, consider hiring professionals. They spot issues you might miss. It's worth the investment for tricky openings.
Step-by-Step Measuring Guide
Now for the crucial part. Follow these steps exactly. Missing one detail could mean ordering wrong-sized internal bifold doors.
Step 1: Check Opening is Square
Your opening might look straight. It probably isn't. Most UK homes have slight variations.
The Diagonal Test:
Grab your tape measure. Stretch it from the bottom left corner to the top right corner. Write down the measurement. Now measure from bottom right to top left.
| Measurement | What It Means | Action Required |
| Both equal | Opening is square | Proceed to Step 2 |
| Difference <5mm | Slightly off | Note it, but continue |
| Difference >5mm | Significantly uneven | Consider professional help |
If measurements differ more than 5mm? You've got options. Adjustable track systems can compensate. Or hire a carpenter to square the opening first.
Step 2: Measure Width
Never trust a single measurement. Walls aren't perfectly straight.
Three-Point Width Check:
Top measurement - Place tape at the highest point
Middle measurement - Exactly halfway down
Bottom measurement - At floor level
Record all three numbers. Circle the smallest one. That's your working width.
Now comes the critical part. Deduct 10-12mm for fitting tolerance. This gap allows proper installation. Without it, your doors won't fit.
For internal aluminium bifold doors, remember the frame adds 75mm. Standard timber frames are thicker at 95-120mm. Factor this into your space calculations.
Quick Formula:
Door Width Needed = Smallest Opening Width - 12mm
Example: Opening measures 1806mm at top, 1802mm middle, 1804mm bottom.
Step 3: Measure Height
Same principle as width. Three measurements give you accuracy.
Three-Point Height Check:
Measure from subfloor to lintel at:
Left side
Centre point
Right side
Use your step ladder here. Don't guess the top measurement. Remove any carpet strips first. You need the solid floor level.
Again, take the smallest measurement. Deduct 10-12mm fitting tolerance.
But wait. Internal bifold doors UK installations need floor clearance too. Add 10-15mm at the bottom. This prevents dragging on carpets or uneven floors.
Height Calculation Table:
| Measurement Type | Adjustment | Purpose |
| Raw height | -12mm | Fitting tolerance |
| After tolerance | -10 to -15mm | Floor clearance |
| Final height | Your order size | Perfect fit |
Real example:
Step 4: Additional Measurements
These extras make the difference between good and perfect fits.
Wall Thickness
Measure at several points. Older UK homes have inconsistent walls. You need the thickest measurement. It affects frame selection and finishing trim requirements.
Track Space Requirements
Top-hung systems need 75-100mm above the opening. Check you have this clearance. Hit a ceiling? You'll need a different configuration.
Measure from lintel to ceiling. Less than 75mm? Consider bottom-rolling tracks instead.
Handle and Hardware Clearance
Where will handles sit when doors fold? Check nearby walls and furniture. Standard handles project 50-65mm. You need clearance for comfortable operation.
Floor Level Check
Place your spirit level across the floor opening. Any slope? Measure the difference between highest and lowest points.
| Floor Variation | Impact | Solution |
| <3mm | Minimal | Standard installation |
| 3-8mm | Moderate | Adjustable bottom guides |
| >8mm | Significant | Level floor first |
Pro Tip for All Measurements:
Create a simple sketch. Mark every measurement on it. Include:
All width points
All height points
Diagonal measurements
Wall thickness
Any obstacles
Double-check everything before ordering. Especially for internal aluminium bifold doors where precision matters more. Their slimmer tolerances mean less room for error.
Remember the golden rule. Measure twice, cut once doesn't apply here. Measure three times at multiple points. Order once.
Standard UK Sizes and Specifications
Knowing standard sizes saves time and money. Most internal bifold doors fit common UK openings. Let's explore what's available off-the-shelf.
Common Sizes for Internal Bifold Doors UK
UK manufacturers follow fairly consistent sizing patterns. You'll find these everywhere.
Standard Height Options:
2032mm (6'8") - Most common
2047mm (6'7") - Slightly shorter option
2078mm (6'8.5") - Modern builds
2438mm (8') - High ceilings
Single door widths start narrow for cupboards. They go up to full room dividers.
Single Door Width Range:
| Width (mm) | Width (feet/inches) | Best Use |
| 457 | 1'6" | Narrow cupboards |
| 610 | 2' | Standard cupboards |
| 686 | 2'3" | Pantries |
| 762 | 2'6" | Small rooms |
| 914 | 3' | Bathrooms |
Double configurations work for larger openings. They're perfect for internal bifold doors UK room dividers.
Double Door Width Options:
| Width (mm) | Width (feet/inches) | Typical Application |
| 1168 | 3'10" | En-suites |
| 1473 | 4'10" | Home offices |
| 1778 | 5'10" | Bedroom dividers |
| 2136 | 7' | Living spaces |
Most Popular Combinations:
We see these sizes ordered repeatedly:
610 x 2032mm - Perfect for standard cupboards
762 x 2032mm - Ideal bathroom doors
914 x 2438mm - Statement room dividers
These combinations fit most UK homes built after 1960. Victorian properties often need custom sizes.
Minimum and Maximum Dimensions
Not every opening suits bifold doors. There are practical limits.
Minimum Practical Sizes:
Anything smaller? The folding mechanism becomes awkward. Users struggle with narrow panels.
Maximum Standard Sizes:
Need bigger? Internal aluminium bifold doors handle larger spans better. Their strength allows wider panels.
Going Beyond Standard:
Custom manufacturing opens more possibilities:
Widths up to 6000mm possible
Multiple track systems required
Heights up to 3000mm achievable
Professional installation essential
| Opening Size | Track System | Panel Configuration |
| Up to 2.1m | Single track | 2-4 panels |
| 2.1m - 4.2m | Single track | 4-6 panels |
| 4.2m - 6m | Double track | 6-8 panels |
Remember these are finished door sizes. Your opening needs that extra 10-12mm we discussed earlier.
Special Measuring Considerations
Standard measurements don't always apply. Different materials and room types need special attention. Let's explore these unique situations.
Internal Aluminium Bifold Doors
Aluminium changes the measuring game completely. These doors offer distinct advantages over timber.
Frame Comparison:
| Material | Frame Width | Glass Area | Strength Rating |
| Aluminium | 75mm | Maximum | Excellent |
| Timber | 95-120mm | Reduced | Good |
| uPVC | 85-100mm | Moderate | Fair |
Those slimmer frames mean more light enters your room. But they require precise measurements.
Internal aluminium bifold doors support larger glass panels. Single panels can reach 1200mm wide. Timber struggles beyond 900mm. The strength difference is significant.
Weight becomes crucial here. Heavier doors need stronger tracks. Check your ceiling can support them.
Track Requirements for Aluminium:
Heavy-duty runners essential
100mm minimum clearance above
Reinforced fixing points
Professional installation recommended
Maximum panel sizes vary by location. Standard UK homes handle 48" x 96" panels. Coastal areas with high winds? Limit drops to 36" x 96".
Room-Specific Requirements
Each room presents unique challenges. Your measurements must account for these.
Living Room Dividers
Most UK living rooms suit 1800-3000mm wide openings. Measure furniture placement too. Will sofas block folded panels? Check both sides.
Wardrobe Doors
Minimum 610mm width works for single wardrobes. But consider access. Can you reach everything inside?
Louvre panels offer ventilation. They prevent musty smells in closed spaces. Measure for slightly thicker panels though.
Kitchen Dividers
Appliances complicate things. Account for:
Bathroom Installations
Moisture changes everything. Internal bifold doors UK bathrooms need special treatment.
| Consideration | Measurement Impact |
| Ventilation gaps | Add 10mm top/bottom |
| Waterproof seals | Reduce opening by 5mm |
| Floor drainage slope | Check level carefully |
| Extractor fan position | May limit track height |
Unusual Openings
Not every doorway is rectangular. Older UK homes throw curveballs.
Out-of-Square Openings
Up to 10mm variance? Adjustable tracks save the day. They compensate during installation. Measure the maximum variance points carefully.
Beyond 10mm needs attention. Options include:
Frame packing to square opening
Custom-made offset panels
Professional carpenter adjustment
Corner Configurations
Corner internal bifold doors create stunning open-plan spaces. Two angle options exist:
| Angle Type | Best For | Measurement Method |
| 90° corners | Square rooms | Measure each side separately |
| 135° corners | Bay windows | Use angle finder tool |
Both configurations need moving or fixed corner posts. Factor in 100mm for post width.
Victorian Property Challenges
These beautiful homes weren't built for modern doors. Common issues include:
Uneven brick openings (measure every 100mm)
Settlement causing slopes
Non-standard heights (often 2200mm+)
Thick walls requiring extension frames
Measure at more points than usual. Every 200mm horizontally and vertically. Document all variations.
When Custom Sizing Becomes Essential:
Opening varies >15mm in any dimension
Non-rectangular shapes
Heights above 2438mm
Widths exceeding standard tracks
Listed building requirements
Custom doors cost more. But they're worth it for perfect fits.
Common Mistakes and Solutions
Even experienced DIYers make these errors. Learn from others' expensive mistakes. Save yourself the hassle and cost.
Top 8 Critical Errors
Let's tackle the mistakes that ruin internal bifold doors installations.
1. Not Checking Square with Diagonals
People assume openings are square. They rarely are. Skip the diagonal check? Your doors won't fit properly.
2. Forgetting 10-12mm Fitting Tolerance
This kills more projects than anything else. Doors ordered at exact opening size simply won't fit. You need that gap.
3. Single-Point Instead of Three-Point Measuring
Walls aren't straight. One measurement lies. Three tell the truth.
4. Ignoring Floor Level Changes
Floors slope, especially in older homes. Miss this? Doors drag or leave gaps.
5. Not Considering Panel Stack Width
Folded panels need space. Four panels stack to 300-400mm width. Where will they go?
6. Measuring in Wrong Units
Mixing metric and imperial causes disasters. Internal bifold doors UK suppliers use millimetres. Stick to one system.
7. Forgetting Track Space Requirements
Top-hung systems need 75-100mm clearance above. No space? You'll need major changes.
8. Not Double-Checking Measurements
Measure once, cry twice. It's that simple.
| Common Error | Cost to Fix | Prevention Method |
| Wrong tolerance | £200-500 | Always deduct 10-12mm |
| Mixed units | £300-800 | Use metric only |
| Forgot track space | £150-400 | Check ceiling clearance |
| Ordered wrong size | Full door cost | Triple-check everything |
Professional Tips
Some situations scream for expert help. Don't be stubborn.
When to Hire an Expert:
Opening variance exceeds 15mm
Internal aluminium bifold doors over 3m wide
Listed buildings or conservation areas
Structural modifications needed
You're just not confident
Professionals spot issues immediately. They've seen every problem before. Their experience saves money long-term.
Documentation Best Practices:
Create a measurement sheet. Include:
Keep everything until installation completes. You'll need it for queries.
Manufacturer Consultation Importance:
Different brands have different requirements. Call them before ordering. Ask about:
Their specific tolerance requirements
Maximum panel sizes they recommend
Track system specifications
Adjustment capabilities
Free advice prevents expensive mistakes. Most UK suppliers offer measurement guides. Use them.
After Measuring: Installation Planning
Choosing Your Doors
Numbers in hand, we turn measurements into a spec. Use the smallest opening width minus 10–12 mm. Height follows the same rule, plus 10–15 mm floor clearance. Now pick size, material, configuration, and track.
Quick size-to-setup guide
| Opening width (mm) | Typical setup | Notes |
| 1168–1500 | 2 panels | Cupboards, compact rooms |
| 1501–2100 | 3–4 panels | Everyday internal bifold doors |
| 2101–3000 | 4–6 panels | Room dividers, wider spans |
Standard vs Custom (cost & timing)
Standard sizes: fastest sourcing, strongest pricing. Fewer onsite adjustments.
Custom sizes: solves non-standard UK openings. Expect ~15–35% premium, longer lead times.
Tip: adjust plasterboard or liners before ordering custom. It often pays back.
Material selection for your opening size
Internal aluminium bifold doors: 75 mm slim frames, excellent rigidity, larger panels up to 1200 mm. Ideal for 2.1–3.0 m spans.
Timber: warmer look, thicker frames 95–120 mm, best under 900 mm panel widths.
uPVC: budget friendly, moderate spans, bulkier sightlines.
Configuration decisions
Fold direction: push stacks toward clear space, not sockets or radiators.
Panel numbers: balance passage width, stack width. Rule of thumb: stack ≈ panels × 75–100 mm.
Traffic door (lead door): daily access, multi-point locking, smoother flow.
Installation Checklist
✅ Confirm every dimension twice; use three-point checks for width and height.
✅ Specify opening direction; mark hinges and stack side on the sketch.
✅ Choose track type: top-hung preferred for clean floors; bottom-rolling suits low headroom.
✅ Verify headroom: 75–100 mm clear space above for tracks and fixings.
✅ Check floor level; plan shims or guides if variance exceeds 3–8 mm.
✅ Lock hardware choices: handle projection 50–65 mm, safe clearance on both sides.
✅ Timeline: measure day, order day, lead time, delivery, acclimatisation, install day, snag list.
✅ Budget professional installation: £150–£300 per set in the UK; location and spec influence price.
✅ Prepare site: remove old doors, clear 1 m each side, protect floors, confirm power access.
✅ File everything: sketches, photos, all readings, supplier spec sheets for internal bifold doors UK orders.
Quick Reference Guide
Measurement Formula Summary
Door width = Opening width − 12 mm
Door height = Opening height − 12 mm
Stack width = Panel number × 75–100 mm
Minimum opening = (Panel width × panels) + tolerance
Use smallest reading from three-point checks.
Keep 10–15 mm floor gap for smooth glide.
Nominal ≈ actual + 12 mm; label differs by design.
Size Conversion Table
Metric ↔ Imperial quick picks
| Metric | Imperial (approx.) | Use case |
| 12 mm | 1/2 in | Fitting tolerance |
| 75 mm | 3 in | Slim aluminium frame, headroom min |
| 100 mm | 4 in | Upper headroom, heavy tracks |
| 400 mm | 15.75 in | Odd-panel minimum |
| 610 mm | 24 in | Cupboards, wardrobes |
| 762 mm | 30 in | Bathrooms, small rooms |
| 914 mm | 36 in | Wider passage |
| 2032 mm | 80 in | Standard UK height |
| 2078 mm | 81.8 in | Modern builds |
| 2438 mm | 96 in | High ceilings |
Standard size chart (internal bifold doors UK)
| Type | Widths (mm) | Heights (mm) |
| Single | 457, 610, 686, 762, 914 | 2032, 2047, 2078 |
| Double | 1168, 1473, 1778, 2136 | 2032–2078 (common) |
Common openings
Living rooms: 1800–3000 mm; plan stack space.
Wardrobes: 610–914 mm; mind handle projection.
Kitchen dividers: 1500–2400 mm; allow appliance clearances.
Bathrooms: 762–914 mm; check ventilation gap.
FAQs About Measuring Internal Bifold Doors
Q: How much clearance needed?
A: Leave 10–12 mm fitting tolerance around the frame, then keep 10–15 mm under-door clearance for carpets and uneven floors. Always work from the smallest three-point measurement before applying these allowances.
Q: Minimum practical width?
A: 610 mm for a single internal set is the practical minimum. As a guide, odd-panel configs can use ≈400 mm panels; even-panel configs need ≈700 mm minimum per panel for smooth folding.
Q: Maximum standard height?
A: 2438 mm (8 ft) sits at the top of typical UK “standard” options. Many homes use 2032/2047/2078 mm heights. Taller openings move to custom kits or alternate track arrangements.
Q: Can doors be trimmed?
A: Limited trimming only—about 5–10 mm total dependent on brand and stile construction. Avoid cutting into hardware zones. When possible, order to size using nominal ≈ actual +12 mm conventions.
Q: Different requirements for aluminium?
A: Internal aluminium bifold doors use slimmer frames (~75 mm) and support larger panels (up to ≈1200 mm), yet the measuring method stays the same: three-point checks, subtract 10–12 mm, verify 75–100 mm headroom for tracks.
Q: What if between standard sizes?
A: You have options: adjust the opening using liners/packers, change panel count or configuration, or specify a custom set. Confirm nominal vs actual sizing delta (≈12 mm) and the required clearances before ordering.
Why Choose Derchi Doors and Windows for Your Internal Bifold Doors
About Derchi Excellence
Industry leader in premium internal bifold doors for UK homes and projects.
Specialist focus on internal aluminium bifold doors for sleek sightlines and strength.
Precision engineering ensures a perfect fit once measurements follow the 3-point method and 10–12 mm tolerance.
Broad catalogue: fast-moving standard sets plus fully bespoke sizes for complex openings.
At-a-glance specs
| Item | Typical Value |
| Frame sightline | ~75 mm (aluminium) |
| Panel width range | 400–1200 mm |
| Headroom for track | 75–100 mm |
| Fitting tolerance | 10–12 mm |
Derchi Product Advantages
Ultra-slim frames: more glass, more light, cleaner lines.
Smooth operation: premium runners, accurate guides, stable stacking under daily use.
Custom capabilities: made-to-measure panels for non-standard UK openings and period properties.
Professional support: we translate your measurements into exact order sizes; clear drawings, hardware advice.
Quality guarantee: robust warranties; components selected for longevity and low maintenance.
Get Your Perfect Fit with Derchi
Free measurement consultation; we review your three-point readings before you order.
Guided resources: printable checklists, measurement templates, quick formulas in plain English.
UK-wide installation network; vetted teams, clear timelines, tidy handover.
Custom manufacturing for irregular widths, taller drops, corner sets, multi-panel rooms.
Ready to proceed on internal bifold doors UK projects? Talk to Derchi today; share your opening sizes, preferred configuration, and we’ll map the optimal internal aluminium bifold doors package.
From Measurements to a Perfect Fit
Nail the measuring, and your internal bifold doors will work beautifully. Start by checking the opening is square using diagonals. Record width and height at three points; use the smallest number. Subtract 10–12 mm for fitting tolerance and keep a 10–15 mm floor gap. Confirm 75–100 mm headroom for tracks. Remember: nominal size usually equals actual size plus 12 mm. Plan configuration and panels early—estimate stack as panels × 75–100 mm. For internal bifold doors UK projects, many openings match standard sizes; go custom when walls vary, heights rise, or access needs a traffic door.
Choosing internal aluminium bifold doors brings slim ~75 mm frames, larger panels, strong operation—accuracy matters even more.
Need help from measurement to install? Derchi Doors and Windows provides clear guides, specification checks, and a UK-wide network to deliver the right doors, fitted right, first time.
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