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KNOWLEDGE HUB

Everything You Need Before You Buy.

Four essential guides covering UK planning permissions, precise measuring, foundation requirements, and how to care for your structure across every season.

Planning & Permission Measuring Foundations Maintenance

Measuring the space a pergola will stand in before ordering

Accurate measurements are the single most important factor in a successful pergola installation. Errors at this stage cascade through every subsequent step — from incorrect post positioning to structural misalignment. Measure twice. Photograph everything.

Tools You Need

Laser distance meter (preferred)

Accurate to ±1mm. Stand at one wall and fire toward the opposite point. Record width and depth separately from the same reference corner.

Steel tape measure (minimum)

If using a tape, have a second person hold the far end taught. Avoid measuring on a diagonal — always measure parallel to walls and edges.

Spirit level or plumb line

Used to confirm your reference wall is vertical and your ground surface is acceptably level. A slope greater than 30mm across the intended footprint will need to be addressed before installation.

Measuring Width & Depth

Always measure from the inside face of any wall or fence the structure will attach to — not from the outside face. Your pergola dimensions refer to the finished external frame size, so measure to where you want the outer edge of the post or beam to sit.

Width

Parallel to the attachment wall, from post centre to post centre

Measuring to the outer wall face rather than post centre

Depth (projection)

Perpendicular to the wall, from wall face to outer post centre

Forgetting to subtract the wall-bracket standoff (typically 80–100mm)

Height

Ground level to intended underside of beam, at the wall

Measuring to the top of the beam rather than the underside

Checking for Square Corners — The 3-4-5 Method

If your installation area has walls or fences on more than one side, confirming square corners is essential. An out-of-square space will create misalignment in post positioning and visual discrepancies in the finished structure.

Mark 3m along one wall from the corner

Use chalk or a stake to mark the 3m point along your reference wall.

Mark 4m along the adjacent wall

From the same corner, mark 4m along the wall at 90° to the first.

Measure the diagonal between the two marks

If the corner is perfectly square, the diagonal will measure exactly 5m. If it doesn't, note the discrepancy and include it in your suitability assessment.

Pro Tip

Most residential gardens are not perfectly square. A discrepancy of up to 30mm across a standard bay is generally accommodatable during installation. Anything beyond this should be discussed with your advisor at the detailed quotation stage.

Circulation Space — The "Action Zone"

Allow a minimum of 900mm between any pergola post and an adjacent wall, fence, or fixed furniture. For comfortable movement of two people passing, 1,200mm is preferred. This clearance affects post positioning and is critical in narrow spaces.

Rule of Thumb

If your total available depth is less than 2.4m, discuss post placement options with your advisor before ordering. Some configurations allow posts to be moved closer to the wall to preserve usable space.

Height Considerations

Our standard frame heights range from 2.2m to 3.2m to the underside of the beam. The most commonly requested residential height is 2.4m — comfortable for clearance under the beam whilst remaining within Permitted Development limits when close to a boundary.

Remember: if you are within 2m of a boundary, the total structure height (to the top of the outermost roof element, not the underside of the beam) must not exceed 2.5m. Factor in louvre depth — typically 80–100mm above the beam — when confirming compliance.

Photo Requirements for Your Assessment

Photos submitted with your suitability assessment form allow our advisors to verify your measurements and identify any site-specific considerations that might not be obvious from dimensions alone.

The wall the pergola attaches to

Full-width shot showing the entire wall face, including doors, windows, and any obstructions. Taken from 3–4 metres back, portrait orientation.

Ground surface across the footprint

Showing the full area where the structure will sit. Include any level changes, drains, or features within or near the footprint.

Access route from the street

Including any gates, steps, narrow passages, or overhead cables along the path your HIAB delivery vehicle will need to navigate.

The show pergola at dusk with its LED strips on

WANT TO SEE THE SHOW PERGOLA?

See the Engineering In Person.

Our single full-size show pergola is at our Sutton, Retford premises, and viewings are by appointment. Book a viewing on the showroom page, where you can send the dates and times that suit you. Or use the form below to send approximate sizes and photographs. We aim to return an initial budget estimate within a few working days; if it suits your budget, we then move to the detailed specification, CAD drawings and firm written quotation.