Fire Doors Guide UK

FD30 FD60 fire rated doors prices specifications internal and external fire doors for homes and businesses UK building regulations compliant fire door sets.

A Step-by-Step Guide to Measuring for Your New Folding Door Set

You have found the perfect folding door system. You have chosen your finish—perhaps a beautiful prefinished oak or a crisp white primed. You have decided between the seamless Roomfold 3-in-1 and the floor-transitioning Roomfold Multi-Room. Now comes the most critical step in the entire process: measuring your opening.

In the world of doors, the old adage "measure twice, cut once" is absolutely gospel. An error of just a few millimetres can mean the difference between a perfect, professional installation and a costly, frustrating disaster. Folding door sets are precision-engineered systems. They are designed to fit specific opening sizes with allowances for fine-tuning, but they cannot compensate for a fundamentally incorrect measurement.

This guide will walk you through the process step-by-step, explaining exactly what you need to measure, what terms like frame height and frame depth really mean, and how to ensure your new doors fit perfectly first time.

⚠️ PROFESSIONAL TIP: Never assume your opening is perfectly square. Walls settle, floors shift, and corners are rarely perfect 90-degree angles. Always measure in multiple places!

Why Accuracy Matters More Than You Think

Before you pick up your tape measure, it helps to understand why this stage is so crucial. Modern door systems, like the Roomfold range from Doors Online UK, are not just wooden frames; they are engineered kits.

• Factory-Cut Components: The frames, tracks, and doors are cut and assembled to specific dimensions. They arrive on site ready to install.
• Tight Tolerances: These systems are designed to operate smoothly with minimal gaps. Too much space and the doors will rattle and lose heat/sound efficiency. Too little space and they will bind, stick, or fail to close properly.
• Hardware Integration: The pivot points, guide rails, and hinges are all positioned based on your overall measurements. A mistake here can throw the entire mechanism out of alignment.

Put simply, accurate measurements are the foundation of a successful installation.

Tools You Will Need

• A good quality tape measure (a steel tape is best; fabric tapes can stretch).
• A pencil for noting measurements.
• A spirit level to check if your opening is square.
• Paper to record every measurement clearly. Do not rely on memory!

Step 1: Understand the Key Terminology

When looking at door specifications, you will see specific terms. Understanding these now will save confusion later. Looking at the Roomfold systems, note these typical dimensions:

Frame Height

2078mm / 2060mm

Internal vs External

Frame Depth

78mm / 133mm

Internal vs External

• Frame Height: This is the overall height of the door frame unit. For the Roomfold 3-in-1 and Multi-Room internal sets, this is typically 2078mm. For the External Quality Patio system, it is 2060mm. Your opening needs to accommodate this.
• Frame Depth: This is the thickness of the frame from front to back. Internal systems like the 3-in-1 and Multi-Room have a frame depth of 78mm. The external quality system, needing more insulation and hardware space, has a deeper frame of 133mm. Your wall thickness needs to accommodate this.
• Trimming Allowance: This is your safety net. Most systems, including all Roomfold sets, allow for a 20mm trim on height and specific allowances on width (e.g., 20mm on two doors, plus an extra 10mm per door thereafter). This allows for fine-tuning on site, but it is not a substitute for accurate initial measurements.

Step 2: Measure the Width (Three Times!)

The width of your opening is the most common source of errors. You must measure in multiple places.

1. Measure at the Top: Run your tape measure from the left masonry/wall to the right masonry/wall, right across the top of the opening. Record this measurement.
2. Measure at the Middle: Do the same thing at the middle height of the opening.
3. Measure at the Bottom: Do the same thing across the bottom of the opening, close to the floor.

Why three measurements? Walls are rarely perfectly straight and plumb. The top, middle, and bottom widths can vary by several millimetres, or even centimetres in older homes.

Which measurement do you use? You should use the narrowest of the three measurements as your starting point. This ensures the frame will fit everywhere. The trimming allowance can then be used to adjust for the slight variations.

Step 3: Measure the Height (Left, Right, and Centre)

Just like the width, the height of your opening can vary, especially in older properties where floors may have settled.

1. Measure the Left Side: Measure from the finished floor level up to the top of the opening on the left-hand side.
2. Measure the Centre: Measure from the finished floor level up to the top of the opening in the centre.
3. Measure the Right Side: Measure from the finished floor level up to the top of the opening on the right-hand side.

Critical Warning: Remember to account for your finished floor level. If you are installing the doors before your final flooring (like tiles or wood) is laid, you must add the thickness of the future flooring to your measurement. A common mistake is measuring to the subfloor and then finding the doors are too tall once the new floor is down.

Again, use the smallest of these measurements as your baseline.

Step 4: Check for Square

An opening can be the right width and height but still be out of square. This means the corners are not perfect 90-degree angles.

To check for square, measure the diagonal distance from the top left corner to the bottom right corner. Then measure the diagonal from the top right corner to the bottom left corner.

• If the two diagonal measurements are equal, your opening is perfectly square. Congratulations!
• If the measurements differ, your opening is out of square. The amount of difference tells you how much. The trimming allowances on your door system (the 20mm allowances) are designed to accommodate a slight lack of square, but significant differences may require you to build out the opening with timber packers or, in extreme cases, have a builder correct the opening structure.

Step 5: Measure the Depth (For Frame Fit)

Remember those frame depth specifications? Now you need them.

Measure the depth of your wall opening (the thickness from the finished internal wall surface to the finished internal wall surface on the other side).

• For a standard internal stud wall or partition, a 78mm deep frame (like the Roomfold 3-in-1 or Multi-Room) is usually perfect.
• For an external wall or a particularly thick internal wall, you may need the 133mm deep frame (like the External Quality Patio system).

The frame needs to sit comfortably within the wall depth. If your wall is deeper than the frame, you will need to use architraves or build out the surrounding wall to create a neat finish. If your wall is shallower than the frame, the frame will stick out, which is generally undesirable.

Step 6: Consider the Headroom and Reveals

Look at the space above the opening (the headroom) and to the sides (the reveals).

• Headroom: You need enough flat wall space above the opening to mount the top track. The installation instructions for your specific door set will specify the minimum headroom required.
• Reveals: You need enough flat wall space on either side of the opening for the side jambs of the frame to sit flush. Also, consider the "stacking space." When the doors are fully open, the folded door leaves will stack against one side (or both sides, depending on your configuration). You need enough clear wall space next to the opening to accommodate this stack width.

Step 7: Record Everything and Consult the Professionals

You now have a set of critical measurements:

• Minimum Width (from top, middle, bottom)
• Minimum Height (from left, centre, right)
• Diagonal Measurements (to check square)
• Wall Depth

With these figures, you are ready to look at the specific product details. For example, you can now confidently see if your opening width falls within the ranges offered (e.g., 1215mm - 3502mm for the 3-in-1) and if your height is compatible with the 2078mm frame height.

A Final Word of Advice:

If at any point you feel unsure, or if your measurements reveal significant irregularities in your opening, do not guess. A mistake here is expensive.

Contact the Supplier: Companies like Doors Online UK have experienced teams who can review your measurements and offer guidance. They deal with this every day.

Hire a Professional: Paying a qualified installer or joiner to measure and fit your doors is money well spent. They will know exactly how to handle out-of-square openings, uneven floors, and tricky reveals.

Accurate measuring might seem daunting, but by following these steps methodically, you arm yourself with the knowledge needed to ensure your beautiful new folding doors fit perfectly, operate smoothly, and transform your home for years to come.

Fire Doors Guide UK

FD30 FD60 fire rated doors prices specifications internal and external fire doors for homes and businesses UK building regulations compliant fire door sets.

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