Knowledge base
Does a pergola base need to be level?
The difference between a level frame, a drainage fall and an uneven mounting surface.
The mounting points must meet the level and fall tolerances in the pergola manual. That does not always mean the whole patio is perfectly flat: a roof or gutter system may need a designed fall, while the post bases still need stable, correctly aligned support.
Harbour Lifestyle tells buyers to check patio fall before installation and describes approved packers used to fine-tune level or introduce drainage fall for its products. It also recommends a site survey where a garden slope or uncertain groundworks make the base suitability unclear.
Do not use loose wedges, scraps of timber or an unapproved stack under footplates. A packing arrangement affects bearing, anchor engagement and water collection around the post. Ask the manufacturer what material, maximum thickness and bolt detail it accepts.
Set out all post centres from the technical drawing before foundations or paving are finished. Check diagonals as well as levels: four individually level pads can still be in the wrong positions or out of square. A made-to-measure screen or louvred roof is less forgiving than an open timber frame.
Plan where rain goes. An integrated gutter needs a clear outlet and the patio should not direct water towards the house. Levelling the pergola by blocking a drainage path simply moves the problem.
If the site has a substantial slope, ask for a designed foundation or stepped-base detail rather than trying to correct it entirely with packers. The supplier can then confirm whether standard posts and screens still fit.
Sources
- Harbour Lifestyle: pergola ground preparation — accessed 14 November 2026.
- Harbour Lifestyle: assembly and installation guides — accessed 14 November 2026.
See pergola bases and fixings, rain and guttering and the glossary definition of a footplate.