Building A Pergola on Concrete

Building your pergola on a concrete slab is fairly simple for both attached and freestanding pergolas. Some people may already have a concrete patio slab and want to know how to build a pergola that will cover the slab.

The pergola is the same construction for flat roof pergolas or gable roof pergola with some small differences. The first is that the posts must be bolted to the concrete slab via a galvanised metal bracket. However, your concrete slab should be a minimum of 100mm or 4 inches thick to provide enough strength for the masonry anchors or bolts.

What to do if your pergola slab is too thin?

In this case you must cut a 300mm x 300mm hole at each post position and dig down to a minimum or 450mm (600mm minimum for freestanding). Then concrete in galvanised metal stirrups in the normal way and finish the concrete level with existing slab.

Step one: Pergola Set Out

Many of existing concrete patio slabs will be around 100mm thick so you can just bolt straight to it. Set out your pergola using builder’s chalk string to make sure that your pergola is square to the house or the existing slab. Once you have marked the exact position by referring to pergola span tables for spacing and size you are really to install post brackets.

Step two: Install Pergola Post brackets

Install your brackets by bolting them down to the concrete. You can use expanding bolts or chemical set bolts to secure your brackets down.

Step three: Build your basic pergola frame

The next part or your pergola is to build the basic pergola frame of posts and beams. If it is an attached pergola make your connection to the house and then build from there. However if building a freestanding pergola, build straight up from the slab with the brackets you have bolted into position.

You can build ether a flat roof pergola or a gable roof pergola on a concrete slab. The main thing is that the concrete is enough to support the pergola. If you have a strong slab building your pergola is fairly easy because your footings are just a bolted down galvanised brackets.

Tip: if you live near the sea or a salty area use only 316 grade stainless for all fittings as galvanised brackets and masonry bolts will rust.