Decking post anchours

[davphi338]

Hi,

I'm fitting some decking 5mx5m on a sloping section of garden, the lowest portion of the decking is at ground level and the hightest approx 1.2m. Its been recommended that I use 9 4x4 post with 6x2 joists, the posts are to be supported by post anchours similar to metposts.

The metposts are the long type that normally just hammer into the ground but I've been told to concrete them with a hole 600mmx600m and approx 400mm deep. Is it OK to concrere those sort of metposts because from the metpost website the ones that they recommend concreteing in are shorter with a square base rather than the long pointed ones.

 

[megawatt]

You need one of these ...

http://www.fencingtrade.co.uk/acatalog/Kwik_Posts.html

3/4 of the way down the page "Concrete Post 4" x 4"

 

[davphi338]

Thanks for the reply,

Yes I agree that is the post designed for concreteing in but the decking was supplied as a kit with the post anchours. The post are of the spike type but the supplier of the kit recommends that once the joists have been assembled and fixed to the posts the post anchour should be dug out to a depth of approx 400mm and then concreted in for extra support. I am just a bit concerened that because these posts are not the ones designed to concreted in they may not be suitable. Will it cause any harm to the post anchours by concreteing them in.

 

[megawatt]

The concrete post anchors are designed to spread the load across the footing for maximum support (vertically) whilst my guess is that the manufacturer is recommending concreting to provide lateral stability (horizontal) as concreting these pointed anchors will not affect their ability to bear loads.

These are more normal for supporting lateral loads (fence posts for example).

A 5x5M deck 1.2M off the ground is quite a substantial structure, one of the most important aspects of which being it's posts, piers and footings ... I would use anchors designed for the purpose of bearing loads

I would dig all of the footings approx 12" - 18" diameter by 2' deep (or deeper if the ground is soft ... Dig to the stony layer) and bell out the bottom third of the hole to give an inverted Y shape. Doing it this way will provide the same degree of load bearing capacity as digging out a 600mm diameter hole and save on backache and concrete.

Make sure you pour the concrete using a form so that the top face holding the post anchor is a 4" above ground level to keep the post end dry.

Don't forget that, for a deck this high, building regs apply regarding railings (basically you need them and a 4" ball cannot pass between any of the spindles).

Thermo usually has good advice on decks so you may find it useful to search for some of his previous posts (I have replied to quite a few previously also).

Good luck

MW