Fixing timber to the rear of a wall without rear access?

[CaptainJack88]

The best way to explain this is with a picture.

We have an existing fence between the neighbors. We can't take it out and get access from their side, as they have lots of stuff in the way, and it'd mean dismantling a lot of their garden. No go.

We had some builders in a while ago, and they built a wall in front of the fence, and eventually, off the top of the wall we would build a slatted fence. To cut a long story short, they messed up the plum line of the wall, as well as finishing it correctly which means we can't build the fence off the top of the wall as intended.

With this in mind, we're going to put some 25mm thick posts behind the wall and between the fence as can be seen below, and then build the fence off this, securing it properly with some 100x100 fence posts at either end.

The issue I'm having, is getting a good secure fixing of the timber to the wall. Does anyone know of best to do this, when access behind the wall is rather limited? Ideally, i'd like some sort of large, threaded plate. This way, i can drill my holes, screw the threaded plate into the back on the timber, drop it into place and then tighten it up with a threaded bar, hex bolt or similar.

The only issue is, I can't find anything like this on the market? Best thing I can find are some M12 nuts and 40mm square washers.
Any ideas?

.

 

[johnny2007]

T- nuts on timber and bolt through the wall

 

[CaptainJack88]

T- nuts on timber and bolt through the wall

I had considered this, but the wall is only 60cm tall and the fence post is 2m, and I can't get a hole in the ground, so the wall fixing needs to be really secure. Those T-nuts don't really spread the load enough. It's only treated pine, so they'll pull right through it

 

[freddiemercurystwin]

If you don't over tighten them T-nuts will not pull through a bit of 25mm timber.

Or what about plate nuts?

 

[CaptainJack88]

If you don't over tighten them T-nuts will not pull through a bit of 25mm timber.

Or what about plate nuts?

I did have a look at plate nuts as well, but the only ones I could find were where the thread comes in from the front. None of the stainless steel ones I could find have a hole in the back for a thread to come through. Unless im looking at the wrong thing

 

[freddiemercurystwin]

I still don't know what's wrong with T nuts, isn't M12 a bit overkill?

 

[CaptainJack88]

I still don't know what's wrong with T nuts, isn't M12 a bit overkill?

The wall itself is 4m wide and only 60cm high, so the only concreted posts are going to be that far apart. The slatted panels are 3m wide.
The fence is 2m high, so over the span of 4m, I need something that is going to take the flex of a 1.6m fence that'll have wind blowing against it.

It's got to hold up, and a T-Nut is going to put a lot of pressure onto 1 point on a piece of timber. Something like a plate nut is going to spread that pressure across a bigger area. Still not decided what to do here, might get a piece of stainless steel bar, glue to to the timber so I can drop it in and thread it through. Will give it a bit more structure and wont let it bend as much

 

[freddiemercurystwin]

Is the wall a thick wall?

 

[CaptainJack88]

Is the wall a thick wall?

100mm.

 

[jono_h]

Surely it’s more likely that a 25mm thick timber is going to snap with the weight of 1.6m of fence blowing in the wind?

These look like they might take a thread from both sides or just recess the stub into the timber.

M4 M5 M6 M8 M10 Carbon Steel Tee Spot Slab Based T Tee Shape Weld Nuts Top Pips | eBay

15mm pip to pip (c). 11mm pip to pip (c1). If there are any problems, then we will try to resolve them for you. We have many years experience in the automotive components and fasteners industry. 6mm Full Length Spire (h).

www.googleadservices.com

 

[freddiemercurystwin]

Or dislodge the blockwork.

 

[johnny2007]

Let me get this straight: you want to build a fence in front of an existing fence.
And the initial idea was to build it on top of the wall, hence losing space in your garden.
Correct?

 

[CaptainJack88]

Surely it’s more likely that a 25mm thick timber is going to snap with the weight of 1.6m of fence blowing in the wind?

These look like they might take a thread from both sides or just recess the stub into the timber.

M4 M5 M6 M8 M10 Carbon Steel Tee Spot Slab Based T Tee Shape Weld Nuts Top Pips | eBay

15mm pip to pip (c). 11mm pip to pip (c1). If there are any problems, then we will try to resolve them for you. We have many years experience in the automotive components and fasteners industry. 6mm Full Length Spire (h).

www.googleadservices.com

I've got actual posts getting concreted in at either end of the wall. It's a slated fence, so wind can pass through it

Or dislodge the blockwork.

I'm putting a few in to spread the weight. Shouldn't be too much of an issue

Let me get this straight: you want to build a fence in front of an existing fence.
And the initial idea was to build it on top of the wall, hence losing space in your garden.
Correct?

We asked them to put actual posts into the ground behind the wall when they built it, but then they took it upon themselves to decide the wall would be too far into the patio if we did that... So now, rather than having the planted 9cm further out, I'm trying to figure out a way to do it for this section retrospectively. Then when I get around to building the other planters myself, I'll put fence posts in first.
The idea is that the fence slats only start where the planter ends height-wise.

 

[johnny2007]

Aren't you over-engineering this?
There's already a fence there, why put another one?
Sorry, I don't understand what you're trying to achieve.

 

[CaptainJack88]

Aren't you over-engineering this?
There's already a fence there, why put another one?
Sorry, I don't understand what you're trying to achieve.

Completely different style of fence. Old one has also had it in places, but posts are on neighbouring side and they don't want to be ripping out all their plants and garden to replace it