Fencing advice - how do I cut into concrete?

Soldato
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Hello,

I want to erect a 1.8 m fence. Currently there is a 0.9 m fence there already. The fence posts which support the current fence are not uniformly spaced. They need to be 1.83 m apart so that the new taller fence panels can slot between them and be held together with metal fence panel hangers.

At the moment the distance between the posts vary. Some are 1.5 m apart, some are 2 m apart.

The fence posts sit inside "channels" on the side of a high concrete wall as shown below.

20180820_102144.jpg


20180820_102111.jpg


My question is what tool do I need to cut new channels into the concrete (as shown in the picture above) so that when the posts sit in the channels, they are 1.8 m apart.

For the curious, I'm going with these Grange closeboard panels.

Thanks
 
Soldato
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Do you need to cut slots at all? It’s going to make a relatively simple job messy and time consuming.

If you want slots I’d guess an angle grinder down both sides and then break out between them.
 
Soldato
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The channels that are currently there look to have been created during the setting of the concrete so you wont be able to recrearte them exactly.

I would suggest you use a stone saw with a diamond tipped blade to cut down each side of the channel you are creating or do more channels if needed and then a lump hammer and flat wide chisel to knock out the concrete between. If you hit the chisel into one of the channels you have created with the stone saw it should split out the concrete pretty easily.

You can rent stone saws from TP or any other builder merchants. Go 2 stroke petrol over electric. Please be careful and dont chop a limb off while you do it.....

EDIT* Otherwise just drill holes and use some decent bolts with concrete plugs to fix the posts right against the concrete. Ensure you countersink them for a tidy job.
 
Last edited:
Soldato
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Do you need to cut slots at all? It’s going to make a relatively simple job messy and time consuming.

If you want slots I’d guess an angle grinder down both sides and then break out between them.
An angle grinder is not really man enough for the job in my opinion. A stone saw will be quicker and more suited for the job.
 
Don
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Last edited:
Soldato
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Do you need to cut slots at all? It’s going to make a relatively simple job messy and time consuming.

If you want slots I’d guess an angle grinder down both sides and then break out between them.

So my boundary finishes at the concrete wall. If I attach my posts to the concrete, then the posts will technically be in my neighbours boundary.

The channels that are currently there look to have been created during the setting of the concrete so you wont be able to recrearte them exactly.

I would suggest you use a stone saw with a diamond tipped blade to cut down each side of the channel you are creating or do more channels if needed and then a lump hammer and flat wide chisel to knock out the concrete between. If you hit the chisel into one of the channels you have created with the stone saw it should split out the concrete pretty easily.

You can rent stone saws from TP or any other builder merchants. Go 2 stroke petrol over electric. Please be careful and dont chop a limb off while you do it.....

EDIT* Otherwise just drill holes and use some decent bolts with concrete plugs to fix the posts right against the concrete. Ensure you countersink them for a tidy job.

It does look like the original channels were created whilst the concrete setted. I was going to rent a petrol tool over an electric as I think I'll power for the job.

Just as an alternative, could you not use those bolt down fence post feet and sit them on top of the concrete. Obviously where you have the slope you would need to create a level for the foot to go.


As above though, if you are intent on cutting channels you would likely want a cut-off saw and diamond blades.
https://www.hss.com/hire/p/cut-off-saw-350mm-14in-petrol

I did look into having those post feet sitting on the concrete level as you suggested. My issue with that is the "sleeve" which the wooden posts sit in doesn't look deep enough to really stop flexing. I.e. to me they don't look substantial. We live in Leeds where we get a high force wind in autumn/winter. Our friend who is a structural engineer in Leeds advised anchoring the fence posts to the concrete wall will be better than metal fence post feet as shown below.

simpson-strong-tie-bases-fpbb44-64_1000.jpg
 
Soldato
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personally I would modify the panels and keep the spacing as it is there.
Or as someone else suggests, fix posts to the concrete wall with bolts.

Depends where you most worried about "the look"

The fence panels are standard size. 1.8 m high and 1.83 m wide. Some posts are more than 1.83 m apart. E.g. some are 2 m apart. If I modify the panels to fit the existing spacing it's going to look naff.
 
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Fair enough

It looks like the fence slopes down in your pic, closest to the camera, how much? pre formed fence panels on slopes are always a pain.
It looks like one post goes basically straight up, your potentially going to have a gap in places if you cannot have the whole fence keeping a consistent angle
 
Soldato
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BTW, that fence looks quite new and nice (imho) why do you want to change?

Privacy :) Our neighbours are amazing but we could do with privacy. On the right of the picture is our nighbours house which sits lower than ours, and the nieghbour to the left (you can't see in the image) sits higher than ours.

Fair enough

It looks like the fence slopes down in your pic, closest to the camera, how much? pre formed fence panels on slopes are always a pain.
It looks like one post goes basically straight up, your potentially going to have a gap in places if you cannot have the whole fence keeping a consistent angle

I'm going taper the gravel board so that the fence panels stair step. The gradient isn't steep - 10 cm drop for every 1.8 m distance.
 
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Privacy :) Our neighbours are amazing but we could do with privacy. On the right of the picture is our nighbours house which sits lower than ours, and the nieghbour to the left (you can't see in the image) sits higher than ours.



I'm going taper the gravel board so that the fence panels stair step. The gradient isn't steep - 10 cm drop for every 1.8 m distance.

I figured privacy, was just going to ask if you had considered plants growing along to give more privacy.

And yeah thats what i was going to ask if the gradient wasnt too bad if you were just going to use gravel boards to level it up.
Will the steps be consistent? IMHO the worst fences I have ever seen are ones with inconsistent steps. They just look horribad
 
Soldato
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If bolting to the concrete flush isnt an option you will need to cut channels as originally posted. You have two options. Modify the panels to fit the channels and posts that are already there or cut new channels to fit the panels that will be arriving. I think that the first option will be cheaper and less time consuming.
 
Soldato
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If bolting to the concrete flush isnt an option you will need to cut channels as originally posted. You have two options. Modify the panels to fit the channels and posts that are already there or cut new channels to fit the panels that will be arriving. I think that the first option will be cheaper and less time consuming.

The first option is going to look horrible though. If a standard panel is 1.83 m wide, how exactly do you modify it so that it's 2 m wide?

I can always shorten panels and make it look neat - how on earth do you widen panels without it looking dodge?
 
Soldato
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Those posts still look like they stick out of the wall by an inch or so.

Could you not just notch the new posts so they look like they're inset but actually aren't? They'll still have the strength to support the panels if properly secured.
 
Associate
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you risk damaging the concrete with cutting and knocking a channel out

would it be easier to cut the wooden post and then fix in to the concrete with self tapping concrete screws??

it would give the illusion of channels without you neighbors garden sliding into yours
 
Don
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I can always shorten panels and make it look neat - how on earth do you widen panels without it looking dodge?

You can't and I agree that it would likely look terrible.


Might be worth getting a quote from a contractor to cut the concrete? Ultimately it's then a fixed cost rather than you hiring a saw (and anything else you may need e.g. dust suppression), and chewing through however many blades. There's maybe even some specialist equipment to "chase" out the concrete in that way?
 
Soldato
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The first option is going to look horrible though. If a standard panel is 1.83 m wide, how exactly do you modify it so that it's 2 m wide?

I can always shorten panels and make it look neat - how on earth do you widen panels without it looking dodge?
you are dead right. I assumed the gaps were less wide not wider. How does the neighbour feel about making more channels their side, will it not make that concrete wall even more unsightly? Have you considered bolting fence post bases on top or even countersinking the posts into the concrete on top?
 
Soldato
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You can't and I agree that it would likely look terrible.


Might be worth getting a quote from a contractor to cut the concrete? Ultimately it's then a fixed cost rather than you hiring a saw (and anything else you may need e.g. dust suppression), and chewing through however many blades. There's maybe even some specialist equipment to "chase" out the concrete in that way?
A contractor will cost the best part of a grand and the stone saw with blades will be like 50 for the day max. You will use 2 blades in my estimation if that.
 
Soldato
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Those posts still look like they stick out of the wall by an inch or so.

Could you not just notch the new posts so they look like they're inset but actually aren't? They'll still have the strength to support the panels if properly secured.
This would weaken the timber massively, you cant fix the panels to posts that are notched down to 1 inch of timber.... It would snap at the slightest breeze.
 
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