DIY concrete saw cutting foundation for door

[iron]

i'm remodeling our basement. one of the things we would like to do is move the door about 8ft from it's current spot so as to achieve a bathroom layout that makes sense. in doing this, it looks like i would need to cut a 34" long x 12" high x 8" thick chunk of concrete out of my current foundation. see pics. red line is future door.

i'm thinking of renting the hilti DCH 300 from the orange store for $50 for a day.

questions:
1. is this doable?
2. any tips for keeping a level and perpendicular cut for an awkward (low) cut like this?
3. any considerations i should take?

i would plan to rent the vacuum too, to minimize dust.

i realize i would need a temporary header to support my floor prior to installing the final header.

i also have a drain line on the inside of the house near this cut. i may need to cut this for access and then repair. thoughts on how to handle this?

i believe minimum setup charges with a contractor to do this small project would run around $400. for maybe $80 in rental stuff and some hassle, i think i can do it. however, i've never used a concrete saw before (though many other power tools).

thanks

 

[Buzz Saw]

First thing that caught my eye was 34". You are going to all this work for a 32" door? Cut for the biggest door you have room for. Preferably 38" for a 36" door.

As far as cutting it out it can be done but will take some grunt work. The saw won't be able to cut the full 12" you need in a single pass. You are going to have to cut vertical & horizontal(and diagonal ) the pound out chunk & repeat.

When you get close to the depth you want I would use the saw as a grinder and sweep left to right to work it down slowly to finished depth. Hope that makes sense.

Just thought of another thing. Is your depth taking into account for a treated 2x8 for the door to sit on?

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[Lake Girl]

Remember to install a waterproof membrane under sill... stop the potential mitigation of water into the house. The physical size of the saw will only get you so close to ground level unless you over excavate outside the door.

 

[greg13]

ANY electric will suck, they just don't have the power. A gas powered saw will give you a lot more power. Remember too that you are going to create a ton of dust you will want to use water when making the cuts, water & electricity make a bad combination. you will want to seal off the area from the rest of the house with plastic and have a fan going to keep the air moving. Depending on the thickness you may have to cut from BOTH sides of the wall to get through so make sure you have enough room.

 

[Buzz Saw]

Come to think of it they make chain saws for concrete. It might be worth calling a company that has a concrete chainsaw to make the cut. All the cuts could be from the outside. That would help keep the dust and water outside.

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[iron]

yes, it's a lot of work for a little door. i agree. but, our current door is in a really bad spot. a new 36" door will be too big for the new configuration, so we're going with 30".

the wall is 8" thick. my understanding is that most of the rental saws the orange box carries are good for up to 4 1/2" deep cuts. so, i think i can make it through. i think the vertical cuts will be the hard ones since i'm likely to bottom out on the ground before being able to make a long enough/deep enough cut. i guess an angle grinder for that?

the chainsaws look interesting. can't rent those, but it would certainly work if there was a contractor game to use it.

 

[iron]

well, so far i have one quote from a contractor. for $1100. that's not happening.

starting to think that maybe a combination of my rotary drill and an angle grinder with a diamond blade might get the job done. the angle grinder would likely have a better ability to get in tight and close to the slab. PITA? sure. but probably doable. sequence would be something like:
1. drill holes from inside of house at ~1.5" OC (with 3/4" drill bit) along outline of cutout
2. drill vertical holes to swiss cheese the thing
3. put on chisel tool and see how far that gets me
4. use sledge if chisel isn't working
5. use angle grinder to clean up and get close to level
6. if finished surface is poor quality, use jet set and form it up to something nice

do you think this would work? i know it would be a lot effort, but i feel like the noise would be theoretically lower for my neighbors (most work done while inside) and i think i could get closer to my slab to get the right height.



buzz saw: is it 100% necessary to have a wood sill on the concrete? or, is that a nice-to-have thing that would allow me to better attach a sill pan or sticky flashing?

thanks all! not looking forward to this one, but it is what it is.

 

[peakbagger]

I helped someone do this years ago. He drilled a row of holes and then we beat it on with a sledge and it came down. He went through a lot of core bits. Once the slab was on the floor, he had to drill it again to break it into manageable pieces and then we had to grunt the blocks up out of the house. If he figured in his manhours, $1,100 was cheap. I had another friend who had it done with hydraulic chainsaw, a couple of hours and it was done.

 

[sportbikerider78]

I can't see how high the ceiling is, but can you fit a standard size door that rests on the current concrete sill? That wouldn't work if you already have a door that is at the floor level,,,it would look weird.

 

[iron]

the foundation needs to be cut, otherwise the door would have no header in its exterior load bearing wall.

 

[peakbagger]

the foundation needs to be cut, otherwise the door would have no header in its exterior load bearing wall.

I don't agree. Unless there is appropriate reinforcing in the remaining concrete spanning the opening, it should be cut out all the way to the sill. The sill then needs to be re-supported with an appropriately sized header. The header can be supported by either notching a shelf into the concrete on either side or cutting the hole wider and running jack studs down to the bottom of the cut.

If its a low basement, the header can be a issue as it impacts the height of the door. There are ways of beefing up the sill to eliminate the need for the header but it depends on which way the floor joists are running. If the joists are parallel with the wall to be cut, it may not be that difficult if the joists are high enough to fit in the appropriate height header. If you don't have enough height then you need to notch the concrete. until you have enough height. It the joists are running perpendicular to the wall you would need to install temporary supports on the floor joists, then cut back the joists so you can fit in additional headers to build out the sill.

 

[iron]

i'm not following some of the terms you're using, peakbaggger.

the concrete foundation wall at this location is probably 14" tall. if i land an 80" door on top of that, that top of the door would be touching the ceiling, which aside from looking weird, wouldn't work structurally. if you're suggesting that i add a header directly at floor joist level and not underneath the joists like i am planning, this will not work due to my utility chase being right in front of these joists. there's no way i'm screwing with that. demoing the concrete will be way easier.

 

[iron]

does anyone know if it's possible to use a portaband and a blade specific for concrete to make this cut? i'm coming up empty at searches online, but i feel like this should exist. some carbide tipped blade?

 

[Buzz Saw]

does anyone know if it's possible to use a portaband and a blade specific for concrete to make this cut? i'm coming up empty at searches online, but i feel like this should exist. some carbide tipped blade?

No, but you can rent the chainsaw [emoji3]

https://www.sunbeltrentals.com/equipment/detail/929/0200120/14in-gas-concrete-chain-saw/#

This was a quick Google search. It doesn't appear there is a sunbelt in your area but give idea on pricing. $115 for a day doesn't seem to bad.

I don't recall if you ruled out using the chainsaw. I am vicariously living through you with wanting you to rent that chainsaw. I think is would be awesome to run one.

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[iron]

i looked for the chainsaw, but couldn't find a rental. otherwise, i'd be all over it and your dreams could be realized!

 

[Buzz Saw]

Is this place close to you?

http://www.aurorarents.com/equipment.asp?action=category&category=84&key=SAWCCG

You really have me intrigued with the concrete saw.

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[iron]

yep, that store is just down the road. i guess i'll be making a call in the morning. otherwise, it's circular saw + grinder for me.

i do see they require you to purchase the chain, which is pretty lame.

 

[iron]

it looks like plunge cutting is the way to operate this saw. any thoughts about potential kickback issues?

 

[Highbeam]

I have an awesome diamond cup wheel for my 4" grinder that I've used many times to level door sills on slabs or otherwise grind concrete. With one of these you only need to get close with the chainsaw or other method for stem wall removal.

 

[iron]

yeah, i picked one of those up, so hopefully it'll help if needed.

the chainsaw rental price was reasonable. however, you need to buy the chain for $250, so it's a non starter for me. i'll fight the concrete with my circular saw and grinder i guess. boo. would've been fun to use the chainsaw.

 

[Buzz Saw]

$250 dollar chain! [emoji15] .You would think they would have used chains for sale or a deposit on the chain to make it more financially feasible for home owners.

Dang , so close!!



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[peakbagger]

When I used to rent a concrete saw for industrial work, the rental fee was related to a measurement of the depth of tooth loss for the 2' diameter blades. Sawing concrete definitely chews up blades and I expect that that applies to chainsaw blades.

 

[Lake Girl]

Both the concrete and rebar within beats the heck out of the blades... I'm thinking blades are more reliable than chain but have only seen the blades in action.

 

[peakbagger]

I have used both on various projects. Most concrete residential walls have few rebars maybe a few up near the sill. A hydraulic chainsaw is the fastest unless the wall has a lot of rebar in it. Saws really should be set up on track to keep the blade from pinching. For floors I usually had the crews use a saw as it was lot easier to move around. More than a few folks just score the wall about an inch or two deep from both sides and take a jackhammer to it. The concrete generally fractures right along the score mark. Cutting vertically is a PITA as you don't have the force of gravity to help.

If its really full of rebar like industrial foundations I like wire sawing the best. Its a longer setup but it will cut through anything and leave a really clean cut.

I had a couple of 30" diameter holes drilled horizontally 9 feet deep with core drills long ago. Nice clean holes but slow. The contractor went cheap and bought a low quality bit for $12,000, it ended up dull and he had to buy a $16k one that worked fine.

 

[vinny11950]

The right tool for the job may save you time and sloppy work. That chainsaw looks sweet, so for $250, I would buy the chain for the chainsaw. It is a big job so expect to spend some to get it done.

Whatever you do, get a quality P100 mask/respirator. You don't want to be breathing in that silica dust as it can cause lung damage.

Plan on ways to control the dust so it doesn't go inside all over the place. I use the 20" box fan with a hepa filter taped to it so it catches some of the dust.