ᐅ Fence Construction – Installing Posts on an Uneven Sandstone Wall?

Embedding posts in concrete behind the wall is unfortunately not an option. The ground has been built up and will settle over time, causing the fence to sink. The landscape gardener (who built the wall and carried out the fill) strongly advised against this and said that the posts definitely need to be connected to the wall, for example by attaching them from behind with a wall post bracket.

I spoke again with the fence installer on site, and he said this is nonsense. The best way is to core drill into the wall, 20cm (8 inches) deep / 12cm (5 inches) in diameter, shorten the posts, and embed them in concrete—that will hold. So now I’m looking for a suitable core drill bit for sandstone (any recommendations? There are a total of 12–15 holes) or I might have a company do the work...

Changeling schrieb:

Now I’m looking for a suitable core drill for sandstone (any suggestions? It’s a total of 12-15 holes) or I might have a company do it…

Hello Changeling

A company will charge a lot for that. For 12-15 holes, you should expect to pay around a thousand. If you’re reasonably handy, do it yourself. Online classifieds like eBay Kleinanzeigen are a good option. You can rent a core drill with a suitable diamond drill bit for about a hundred euros for 24 hours. Make sure to find one that offers a fixed price including wear and tear on the drill bit. It’s better to pay 20 euros more upfront than to be charged heavily for drill bit wear afterward.

Steven

Changeling schrieb:

The best option is to core drill into the wall, 20cm deep (8 inches) / 12cm diameter (5 inches), shorten the post and set it in concrete,

Keep in mind that for each post you will need to build a kind of support frame, for example from battens, to ensure all posts are levelled in three axes at the end.
Alternatively, wedge the post in the hole until the concrete / fast-setting cement / grout hardens and the post can no longer move.

Steven schrieb:

A company charges a lot for this. You should expect around $1,000 for 12-15 holes.
If you’re not completely inexperienced, do it yourself.

Wow... so it’s not something you can just do quickly. Around here, there are no core drilling machines available on eBay classifieds or rental sites like erento. And I didn’t really want to spend another $1,000 on a fence that costs a bit more than half of that...

Is it really that complicated?

Would it be possible to secure the post to the stone at height using L- or S-brackets and then encase it in concrete, so that we basically go back to the previous option (embedding it behind the wall) — only this way the post couldn’t sink? Or would frost still push it out / could it still sink like that?
Viewed from the side like this:

// Edit: I spoke again with the landscaper. He suggests: Two clamps per post, and additionally securing the lower part of the post with a screw through clamp/post/stone. If needed, add a bit of concrete around it as I suggested above. Apparently, that’s fully sufficient, with reasonable cost and effort. Sounds like a plan!

Changeling schrieb:

He means: two clamps per post, and additionally fix the lower post with a screw through clamp/post/stone. If necessary, add some concrete around it.

It's not about just securing it! The point is that all posts are aligned.
How do you screw your clamp/bracket onto a "crooked" stone?

Hello Changeling

To do it properly (or you’ll regret it for years), you have two options:
1. Core drilling
2. Have the posts welded onto a suitable steel rail, hot-dip galvanized, and install the structure horizontally on the stones. You will also need to drill proper holes into the stone wall.
Anything else is not so good.

Steven