Attaching deck posts to foundation concrete

[jimmington]

Hi all,

First post and hope you don't mind another newbie with a question about deck foundations

I'm installing a small (7.2' x 4.2') deck and steps to provide access from our kitchen to garden which will be just under 2' off the ground.

My plan is to sit the deck frame on six 4x4's. I'm going to set the 3 outer posts in postcrete but I'm unsure of the best approach for the 3 closest to the house, which I had planned to mount in three MetPost brackets, secured with anchor bolts.

I'd wanted to keep the deck floating and avoid a ledger/drilling holes through new render and possibly affecting the DPC.

Having removed the previous old concrete/brick steps that were in disrepair, there is a mix of crumbling concrete with hardcore/sand underneath. Removing this reveals what appears to be foundation concrete (our kitchen having been extended in the 1950s with solid concrete foundations).

Is installing metposts/anchor bolts onto the foundation next to the house OK?

Does it matter that the 3 posts are fixed to foundation and 3 more free-floating in the ground beyond (would that cause stress to the deck frame?)

Thanks for any advice you may have, even if it is "get a builder in!"

Jim

 

[powerst]

I had a similar problem in my old house when I built a deck. I had a massive concrete 'patio', if you could call it that.

My original plan was to break it all up and then use the 4x4 route postcreted in to the ground.

The ones furthest from the house were fine as there was just grass so I dug the holes and inserted the posts. But there was no shifting the concrete unless I got some really heavy duty machinery. I tried a big kango that I hired but it barely made a scratch.

I ended up attaching the frame to the outer posts using coachbolts and then also attached the nearer ones to posts in the same way, but the posts just sat on the concrete. It wasn't going anywhere.

Lasted for 8years with no issues and was still there when we left.

 

[jimmington]

Thanks powerst.

A friend said similar (about it not budging), particularly as it's mainly for access rather than entertaining).

Gut feel is to expose the rest of the underlying concrete (foundations or old concrete 'patio'?) and mount the posts on that if it looks stable and solid.

 

[powerst]

One other thing, just make sure that the water can drain away from the posts and that water doesn't pool around them.

 

[jimmington]

Thought I'd post back with what I ended up doing. The underlying concrete was also weak and insubstantial (gave it a light bash with a sledgehammer)

I ended up digging out the 6 post holes and setting the 4x4's in postcrete. The deck subframe feels really solid (so far )