How to set out your decking frame
There are many ways you can set out your frame. When designing your frame, you must use these standard calculations to ensure the weight loading placed on top of it is supported sufficiently. The design of your decking must include the support posts, beams, joists and decking. The support required is 1.5kN per square metres for an evenly distributed load. So if you would like to know “How to set out your decking frame” do read on…
What are the regulations for decking design
The regulations are derived from BS5268-7.1 which demonstrate the calculations within which you should design your decking structure. There are also wider regulations called Euro Codes (EC) and this EC5 code pertains directly to timber construction. (EC5 is derived from the existing British Standard)
If you are providing a service where you are building a decking structure you must observe these standards and adhere to them. In short, this protects both the client (end user) and also the person building the deck. It enables the deck builder to provide an efficient service and use the correct number of materials. It also protects the client if something goes wrong as the structure will be judged by these standards.
This helpful decking guide assumes the following information
Dimensions of the decking are 3.6 metres deep and 3.6 metres wide
It assumes that the decking manufacturer has specified 400mm joist centres
Beams and joist timbers used are 150mm x 47mm
All timbers are structurally graded C24
The best treatment is to Use Class UC) 4
Posts are 100mm x 100mm (Best in HDPE which is recycled plastic)
Structural fixings are warranted for exterior use such as 150 x 6.5mm Carpenters Mate
Please note that there are many different sizes of decking platform and the decking frame details in this guide are only for a 3.6m x 3.6m low level frame.
For the free download guide for decking structure design go here
Where do I place my Support Posts
Your support posts must be designed to support the beam. If you look at the span tables it clearly sets out where the posts must be placed.
An example being that if your beam centres (this is the distance between the beams) are 1.8 metres. You can’t span your joists over 3.32 metres so by using the span tables we adopt 1.8 metres for the beams because this is at the centre of the structure and will spread the load evenly.
You could use 195 x 47 which is able to span up to 4.11 metres but in most UK decking structures being close to the ground height is an issue.
So now we have a structure with Beams set at 1.8 metres we can use the tables to find our maximum clear span of the joist. In this case it is 1.87 metres
Beam centres at 1.8 metres means that your posts should be no more than 1.87m centre to centre.
Helpful tip “If you find you have posts on every joists you may consider more beams”
Where do I put my Beams
The beams are covered in the above Support Posts section. The design considers the beams in conjunction with the Support Posts. The beams can be placed in a position to enable the joists to sit on top of the beams or be fitted to the side of them.
If height is an issue, then you should fit the joists to the side of the beams. If height is not an issue you then you may fit the joists on top of the beams. How to set out your decking frame is only a simple guide, if you would like someone to design your decking structure contact a pro who will design your deck and cover all regulations.
Where do I put my Joists
If you read your decking manufacturer’s instructions it may be read that the joist centres must be set out at 400mm centres. This means that the centre of one joist can be measure to the next joist centre as 400mm.
Your joists can span between the beams, or you can use them as single pieces and span from one side of the structure to the other.
The detail in “How to set out your decking frame”
This is a simple demonstration for how to use the regulations for a simple decking platform. If you need a perimeter trim detail, laying patterns or a more complex arrangement then you must consider the structure underneath as part of your primary design.
You may require more joists to form the structure to enable a certain pattern of decking. Don’t wait until is built to then decide you would like further detail as the joists won’t be in the right place.
If you need someone to design your decking structure for you click here.
If you would like more information whether to use decking tape or not read this https://deckingnetwork.com/decking-advice/what-is-decking-joist-tape/
