Building platform on existing wall

[samholder]

I want to build a pizza oven at a friends. He has a terrace with a wall around the edge (about 1 metre high - but a large drop on the other side of the wall). The only place that the oven could fit is in a corner of the terrace. We would like to use the existing wall as the level for the oven and want to know what the best way to build a base would be. Ideally the base would overhang the far side of the wall a little, so we could make the oven a little larger.

My initial thought was to use reinforced concrete bars diagonally across the gap and hanging over the edge of the wall slightly (a couple of inches or so each side) and then lay paving slabs or similar on the bars. Then we could build a insulated base on top of this upon which to lay the oven floor.

Does this sound reasonable? Are there better (or even alternative) solutions to this out there?

[dbhansen]

Re: Building platform on existing wall

A picture would really help!

[GianniFocaccia]

Re: Building platform on existing wall

If the perimeter terrace wall happens to be made of filled and reinforced concrete block you're in business. Cantilevered support slabs have been discussed here but need to be poured with rebar that ties into a CMU base and your terrace wall.

[Neil2]

Re: Building platform on existing wall

If an existing structures details are unknown, it is always best to assume that it was designed only for its intended purpose and no more.

Loading the existing wall with the weight of an oven is a big gamble.

I would consider transferring the new weight down to new footings or down into native firm ground. This should be independent of the existing wall and footings. This can be done fairly easily with piles or piers.

Also note that re-bar, by itself (i.e not part of a reinforced concrete structure) has effectively no strength in bending. Your idea of using this as some sort of platform would not work well.

[dmun]

Re: Building platform on existing wall

If there's a retaining wall, there's mystery fill behind it. I'm not sure this is a good idea. What's at the bottom of the retaining wall?

As always, building an oven is a ton of work. You want it to last.

[samholder]

Re: Building platform on existing wall

Thanks for the responses, sorry for the tardiness of my reply.

I have taken some pictures of the terrace to give some idea of its construction.

The walls are concrete block and are built on top of the foundations which support the whole terrace, which is made of concrete bar with the concrete blocks filling in the gaps. Not sure what the name for it is but there are a couple of pictures so it might help.
I've also decided to pour a support slab.

I am also wondering if, by including breeze block supports in the center of the supporting slab not just round the edges, I can reduce the thickness of concrete needed for the hearth? (and hence the weight of the oven). I'm planning on a board base for the oven.



anyway pics:

The breeze blocks outline where the oven will go (corner oven)



As you can see the terrace is raised up from the floor, and the wall is built on top of that. (this is a view from behind the terrace. the oven back will be in that corner.



This is view from below the terrace showing the terrace construction

[cynon767]

Re: Building platform on existing wall

I'm definitely with Neil on this one... You'll want to build up a whole new pier from the ground up if you want to support the weight of an oven that far off the ground. That wall doesn't look like it would hold much free-floating weight. I would consider building a reinforced filled-core cmu pier starting at ground level and going up to the level of the terrace. It would be a lot more work than what you were originally talking about, but would be much less likely to collapse the entire structure. Plus, there's the added benefit that you wouldn't take up as much space on the terrace that way.

[Tman1]

Re: Building platform on existing wall

From what your describing, the oven would actually sit a bit out from those walls on the outside, I think it'll work. Most of the weight would then be on the walls which look to be made of concrete block.

[Neil2]

Re: Building platform on existing wall

Keep the kids away.