Cutting a channel in concrete floor against exterior wall

[dannyrico]

Previously poured concrete ground level too high. I want to cut a channel and fill with pea gravel.

I have a circular saw and SDS chisel, but I worry that’s a chore. Anything I can hire to make it easier? Wondering if I’d be able to get flush/close enough to wall with a disc cutter.

Side note, I don’t see any obvious signs that I’d hit a pipe/cable…but you never know.

What would you do?

 

[robinbanks]

I have a circular saw and SDS chisel, but I worry that’s a chore. Anything I can hire to make it easier?

Take the worry time and apply it to the job instead

I'd go at it with a disc cutter. If you don't have one, make sure the one you hire has a water attachment for dust suppression and definitely get some decent ear defenders because that enclosed space will be deafening

If the concrete runs under the wall, cut a shallow line at the wall joint as upright as you can get the saw, for neatness, then another line close to the wall with the saw blade vertical, max depth, another line that is where you want the trough to end, then several cross cuts (possibly on an angle) at say 4 to 6 inch spacings
Use your SDS to break out the cross cut blocks to give you some room to then breaker out the chunks next to the wall

If the concrete doesn't run under the wall just make the second and third cuts mentioned, proceeding the same

Purple line; cut with saw at steepest angle possible to get an inch maybe 1.5 inch deep cut, if concrete runs under wall. If it butts up to wall don't bother

Green lines - saw blade vertical, max depth

Blue angled lines - whatever angle sees the saw do max depth without crossing the neat green line nearest you( the edge of the pea gravel trough)

Highlighted part: break these out first. The first one you take out might just end up being a destruction job, making more cuts to turn it into Swiss cheese will make life easier, and the cutter will like be more effective/quick than the breaker

If you hire a saw and they charge by the mm for blade wear don't worry; the wear rate is minimal, don't skimp on making cuts cos you're worried about wear; make life easy for the few extra quid

 

[jj4091]

Why do it that way . Use an angle grinder to champher it away from the DPC. I presume that is what you are concerned about

 

[Deluks]

Screw a batten to the floor as a guide, no use marking a line, the dust will obscure it.

Drill and manually smash out the corners.

 

[robinbanks]

no use marking a line, the dust will obscure it.

If you use a saw with a wet suppression system, this doesn't happen; there is no dust, and the blade flings a disc of water that washes the surface ahead, so you can see the line

Always cut wet; your lungs, your neighbours' lungs, and your wallet will all thank you

 

[Deluks]

I wouldn't bother hiring a tool for such a small cut. He mentioned circular saw but assume he meant angle grinder?

 

[robinbanks]

(My local family-owned tool hire place would do a Stihl saw for about 20 quid/day - depending on how one values their time, I'd say it represents a saving over trying the same with an angle grinder)

 

[dannyrico]

All good info so far thanks everyone.

assume he meant angle grinder?

It is in fact circular saw. I entertained the thought to “use what I got”, maybe just buying diamond blade—dust and time were my worry.

I do value my time…and I suspect the concrete has been down at least a decade so quite strong. From what I’m hearing so far it seems worth hiring a wet disc cutter, even if it’s a small area. The wife would be impressed if it’s finished before lunch!