Precast Concrete Post Bases

Types of concrete post bases

This episode of Gadero TV focusses on concrete post bases - precast bases for use as a foundation for canopies and other structures. Concrete post bases are available in various colours and sizes, and range from straight designs for positioning right up against other concrete components, to tapered designs for very heavy-duty builds. The tapered versions, available in 18 by 15 by 50 centimetres in white or anthracite concrete, has a thicker threaded rod, making it suitable for larger projects.

Installing a concrete post base

A concrete post base should always rest on a buried concrete tile. Dig a 30 centimetre deep hole, with a thin layer of fill sand on the bottom. Place the tile on top, and make sure it’s absolutely level. This will form the foundation for the concrete post base.

Next, place the post base on top so that it protrudes from the ground by about 10 centimetres. This has two advantages: it shows off the rugged good looks of the concrete post base, and keeps the post that sits on top free from rising damp.

A bag of fast-setting cement can be added for extra stability. Sprinkle the dry mix in the hole around the post base, and add some water. Then let the concrete harden before continuing your project.

Height adjustment plates

A concrete post base needs a so-called height adjustment plate. Note that not all post bases come with height adjusters included as standard; in some cases, these plates are sold separately.The product descriptions clearly indicate whether or not the height adjustment plate is included with the post base.

Height adjustment plates generally measure 10 x 10 cm; this size is used for posts of at least 12 centimetres in diameter. The project in the DIY video uses 12 by 12 centimetres Larch and Douglas fir beams.

It’s important to start by securing the plates onto the posts before affixing them to the post base using threaded bolts. Make sure to pre-drill holes for the threaded rods in the posts, otherwise it will not be possible to affix the post onto the post base. The diameter of the drill bit should not exceed that of the bolt by too much to prevent loss of stability.

Note that the height adjustment plates do not come with threaded bolts for their installation as standard, so visit our product catalogue to order your threaded wood bolts.

If you want to prepare your posts for lap-jointing, then we recommend doing so before installing the posts to the post bases.

Mount posts on post bases

Next, the post and the height adjustment plate can be affixed to the post by screwing them onto the threaded rod. Be careful, and turn the post as far as possible for maximum stability. Use a corner spirit level to check whether the posts are straight.

We recommend securing the mounted posts using two or more temporary braces. Several battens used as struts can help to keep the posts in place and protect them from high winds. The diagonal braces along the tops of the posts will eventually add permanent structural stability.

Once the posts are mounted onto the post bases and have been secured with temporary battens, you can continue with the next part of the canopy. For more details, have a look at Gadero TV episode 201, which gives you a detailed look at how to install your own deluxe canopy.

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