Pergola base and fixings

A pergola is only as good as what holds it down. Follow the maker's fixing and base instructions. They set the pad size, slab thickness, bolt type and edge distance for the wind and snow figures they publish.

What the makers we read ask for

From retailer and maker pages checked on 13 November 2026:

• Sunnier lists concrete foundations, stone patio or timber decking (with suitable fixings) as suitable surfaces, and reinforced point foundations of 60 × 60 × 80 cm where used, on its Pergola Essential page.
• Pergolux lists concrete, wood deck and patio pavers as installation surfaces, and says anchoring hardware is not included, on its Pergola 4 page.
• Costco's listing for a 3 × 3 m louvred pergola says the base must be firm, flat and level, recommends concrete, slabs or a timber frame, and says not to place it directly on grass, earth or sand.
• Rowlinson's timber pergola listing at B&Q says posts can be sunk into the ground or cut short and used with metal post anchor spikes or shoes.

So the base depends on the product. Get the instructions before you choose the base, not after.

Option 1: an existing patio slab

The cheapest base if it is sound. The questions are whether the slabs are bedded on a full mortar bed or dabs, how thick they are, whether there is concrete underneath, and how close to a slab edge the bolts would land. Bolts into a thin slab on sand can pull out in wind. See fixing a pergola to an existing patio.

Option 2: concrete pads under each post

A pad of concrete under each post, sized to the maker's instructions, with the post bolted down. Common for aluminium pergolas on lawn or soft ground, and for a patio that cannot take the fixings. Plankley works out concrete and slab quantities.

Option 3: ground screws

A steel screw driven into the ground, with a bracket at the top for the post. Quick and no concrete, but only as good as the soil and the screw's rated capacity. Ask the pergola maker whether they accept ground screws for their wind and snow figures. Many publish ratings that assume a concrete base.

We haven't tested this. Figures are as the maker states them (checked 13 November 2026).

Domax galvanised ground screws, pack of 6. Listed on Amazon UK as 80 mm × 685 mm ground screw anchors with a square bracket, for fence or pergola posts. Check the bracket fits your post size, and ask the pergola maker whether this kind of fixing suits their structure before buying.

View the Domax ground screws on Amazon UK

Option 4: decking

Some makers list timber decking as a surface with suitable fixings. The decking frame then carries the post loads and the uplift. Many deck frames were not built for that. Ask the maker, and consider taking posts through the deck to pads underneath. Decking more than 0.3 m high is outside permitted development in England. See planning permission.

Anchoring and wind

Uplift is the load people forget. A roof catches wind from below as well as above, and that pulls the posts up. A heavy aluminium frame still needs bolting down. Use the anchors the maker specifies, at the spacing they specify. Some makers do not include anchors, so check. See wind and snow.

Can I put a pergola straight on the lawn?

Not on the lawn itself. Costco's listing, for example, says not to place its pergola on grass, earth or sand. Use pads, a slab, or a fixing the maker accepts.

Do I need a level base?

Makers ask for level, and louvres and gutters need the frame square to drain and close properly. Check the slab with a level before the kit arrives.