Measuring For a Glass Veranda

Getting accurate measurements is essential when ordering a glass or polycarbonate veranda. Whether you are a homeowner planning a DIY installation or preparing details for a professional quotation, precise measurements ensure your veranda fits perfectly, functions properly, and avoids costly modifications.

This guide walks you through everything you need to know about measuring for a wall-mounted veranda in the UK, including what to look for, common pitfalls to avoid, and important planning considerations.

Before you begin measuring, gather these essential tools:

• Tape measure (at least 5 metres long, ideally 8–10 metres for larger installations)
• Spirit level (to check wall and ground levels)
• Notepad and pencil (or a smartphone for recording measurements)
• Stepladder (for measuring wall heights safely)
• Camera or smartphone (to document the area, including obstacles and mounting surfaces

Step 1: Measure the Width (W)

The width is the total distance along your house wall where the veranda will attach.

• Measure from the furthest left point to the furthest right point where you want the veranda to extend.
• Take this measurement at the mounting height (typically 2.5 – 3.0 metres above ground level).
• Double-check by measuring at ground level as well—walls are not always perfectly straight.
• Obstruction Check: Note any drainpipes, lights, vents, or flues that fall within this width.

Pro tip: If your wall is uneven (bowed or rough stone), take measurements at multiple heights. Most wall profiles allow for some adjustment, but significant bows may require packing or stand-off brackets.

Step 2: Measure the Depth (D)

The depth (also called projection) is how far the veranda will extend outward from your house wall on the horizontal plane.

• Measure perpendicularly from the wall to the point where you want the front posts to sit.
• Consider practical factors:
  • Will you place a dining table underneath? (Allow roughly 3m x 3m for a 4-seater table).
  • Do you need space for bi-fold doors to open fully without hitting the posts?
  • Will the veranda oversail any pathways or borders?

Standard UK projection depths typically range from 2.5 metres to 4.0 metres for wall-mounted systems.

Planning tip: A deeper veranda provides more shelter, but remember that for every metre you project outwards, the roof must slope down, which affects your wall fixing height (see Step 4).

Step 3: Measure the Front Height (H2)

This is the height from ground level to the underside of the front gutter/eaves beam.

• Measure from the finished ground level (including any existing paving or decking) to your desired front height.
• Minimum recommended height: 2100mm (2.1m) is the standard minimum to ensure comfortable headroom.
• Future Proofing: If you plan to add glass sliding doors later, aim for a clearance of 2100mm to 2300mm, as most standard door systems are designed for these heights.
• Check that this height allows tall people to walk freely under the front beam without feeling enclosed

Step 4: Calculate the Wall Height (H1)

The wall height is the point where the wall profile attaches to your house. This is usually calculated rather than chosen freely, because it is determined by your Front Height, your Depth, and the Roof Pitch.

FORMULA:   Wall Height (H1) = Front Height (H2) + (Depth × Pitch Calculation)

Typical Roof Pitches:

• Polycarbonate Verandas: Often flexible, but typically installed at 8° (approx. 140mm rise per metre).
• Glass Verandas: Usually require a specific pitch of 8° to 10° to ensure proper drainage and warranty compliance.
• Flat Roof Systems: Look flat but have a hidden internal pitch (usually minimal impact on wall height).

Worked Example (Standard 8° Pitch):
 If your Front Height (H2) is 2100mm and your Depth is 3000mm:

• Rise per metre at 8° is approx 141mm.
• Total Rise = 3m × 141mm = 423mm.
• Wall Height (H1) = 2100mm + 423mm = 2523mm.

This calculation gives you the height to the underside of the wall profile. You must ensure you have clear brickwork at this height (no obstacles like first-floor windowsills or soffits)

Step 5: Document Obstructions and Site Conditions

Create a sketch or take photos noting:

 Wall-mounted obstacles:

• Drainpipes (soil pipes are particularly large and hard to divert).
• External lights and cameras.
• Gas flues (these often cannot be covered).
• Satellite dishes or alarm boxes.
• Measure the distance from the ground to each obstacle to check if it clashes with your Wall Height (H1).

Ground-level Considerations:

• Existing patio slabs, decking, or concrete.
• Manhole covers (avoid placing a post directly on top of one).
• Uneven ground or slopes away from the house.

Wall Type

• Is it brick, stone, render, or cladding?
• Is the wall vertical? Use a spirit level to check for leaning.

Post Positioning & Cantilever Options

Standard verandas have maximum spans between posts (e.g., usually 3.0m - 7.0m max for glass systems). If your preferred width exceeds this, you will need an intermediate post.
 However, if you want to avoid a post right on the edge of your patio, many systems allow you to inset (cantilever) the posts.

• Inset Posts: You can often move the outer posts in by up to 500mm-1000mm from the edge (check specific model limits). This is great for keeping corners open for access.

Rainwater Drainage & Gutter Systems

Every veranda needs to drain water. Most modern aluminium systems use an integrated gutter where the water runs down inside one of the front posts.

• Surface Discharge: Water exits a hole at the bottom of the post onto your patio.
• Underground Connection: You can connect the post outlet directly to a soakaway or existing drain using standard underground piping.
• Planning: Decide which post you want the water to drain down (usually the one closest to an existing drain or gully).

Future-Proofing: Sliding Glass Doors & Side Walls

If you think you might want to enclose the sides later:

• Ensure your ground is level where the doors will run.
• Stick to standard heights (2100mm - 2300mm under the gutter) to avoid needing expensive custom glass sizes later.
• Ensure the posts are perfectly vertical (plumb) during installation.

FREQUENTLY ASKED QUESTIONS

Q: Do I need planning permission for a veranda in the UK?
 A: Most verandas fall under Permitted Development rights if they are single-storey, rear extensions. Typically, if the height is under 4m (or 3m if within 2m of a boundary) and it does not cover more than 50% of your garden, planning is often not required. However, restrictions apply to listed buildings or designated areas (Conservation Areas, National Parks). Always check with your local planning authority or visit the Planning Portal.

Q: What is the difference between measuring for glass vs. polycarbonate?
 A: The measurement principles are identical. However, glass is significantly heavier. This means glass verandas often have stricter limits on post spacing (usually max 4m between posts) compared to polycarbonate, which can sometimes span wider.

Q: Can I install a veranda on an uneven surface?
 A: The structure itself needs to be square and level. If your patio slopes (which it should for drainage), you will need to adjust the post lengths. Often, installers cut the posts on-site to accommodate the fall of the patio, ensuring the roof remains level.

Q: How accurate do my measurements need to be?
 A: For the initial quote, estimated sizes are fine. For manufacture, aim for accuracy within ±5mm to 10mm. Verandas are engineered products; precise measurements ensure the kit goes together smoothly.

Q: Should I measure before or after I have my patio laid?
 A: Ideally after, so you know the exact finished floor level for your height measurements. If you must measure before, you need to know exactly how much height the new paving will add (e.g., 50mm) and deduct this from your available height under windowsills.

Before ordering your veranda, ensure you have:

• Width (W): Measured along the wall.
• Depth (D): Measured perpendicular from the wall.
• Front Height (H2): From finished floor to underside of gutter (min 2100mm recommended).
• Calculated Wall Height (H1): Confirmed it clears all windows and obstacles.
• Photos: clear views of the wall and ground.
• Obstruction List: Pipe locations, vents, lights noted.
• Drainage Plan: Decided which post will handle the rainwater.
• Ground Type: Confirmed what you are fixing the posts into (concrete pads are usually required under paving)

Taking accurate measurements for your glass or polycarbonate veranda is a logical, step-by-step process. By calculating your wall height correctly and checking for obstacles early, you prevent 90% of common installation issues.

Remember, the goal is to ensure the wall plate fits cleanly on the house and the front clearance is high enough for comfortable use. When in doubt, provide more information—detailed photos and sketches are invaluable for your supplier to spot potential issues before your order is processed.