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Octagonal Deck Construction - How to build an octagonal deck.

A sunken octagonal deck in woodland situation - part of a 5 deck complex - with access via decking steps from patio and 2 other rectangular decks. Octagonal decks put a totally new perspective on decking schemes.

The construction of an octagonal deck presents a few problems, but nothing that can't be overcome with an experienced decking team. (The tree in the deck didn't help, but certainly adds a little (?) something.)

The framework for an octagonal deck is normally built by firstly constructing a regular rectangle - square - then cutting the corners off at 45deg to shape the octagon.

In this instance, the original idea was to have the deck boards radiating around the octagonal shape, but then ideas changed to have the deckboards running 'across' the octagon. This is NOT the easiest or normal way of building an octagonal deck.

The support frame of the octagonal deck is started Octagonal deck subframe starts to take shape

This octagonal had the added dimension of having to be built on a steep slope, and also having to include an existing tree within the shape. The near part of the octagon is near existing ground level and can also be fixed to a section of deck that butts up to it, so support at this edge was not a problem. The rectangular sub frame supports the remainder of the shape, but was set back from the edge so as not to be visible in the finished project. The aim was to have this section of the deck to be 'floating' visually.

 Supports were very important for this octagonal deck Mitered border for the octagonal deck  Deck boards being laid acoross the octagonal deck for added strength

After the octagonal deck section was fixed to the subframe and other support points, the newels for the balustrades were fixed. Before they were fixed, radial deckboards were cut to shape and temporally positioned. The newels were then placed on top of the temporary boards, and marks were made where the boards would be cut to enable the newels to slide down to the sub deck for fixing. Once the newels were fixed to the octagonal deck frame, minor adjustments were made to the 'cut-outs' to ensure that the newels fitted properly through the deck.

 Octagonal decking all laid - the newels for balustrade are positioned

The decking laid on the octagonal deck - allowing 50mm gap around the tree to allow for expansion for the first two years. It was a sycamore tree, so quite quick growing, necessitating enlarging the gap with a jig saw every couple of years or so. If this is not done, then the upward and outward growth movements will eventually lift and distort the deck.   

Octagonal deck blends into the rest of the decking scheme

The balustrades around the octagon call for some careful cutting of the top and bottom rails with accuracy of angle and length being even more important than on straight runs. The balustrades linked the octagonal deck to the main deck section, and as can be seen in the image below, the 'floating' effect was achieved with no supports showing.

The octagonal deck seems to float - as a result of the cantilever work carried out

Plans for your first octagon deck 


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