How best to grind high spots on concrete foundation wall?
JohnWalker
| Posted in Construction Techniques on
Just had the walls poured and they are very good except for a few locations which for one reason or another couldn’t be trowelled as smooth/level as desired. There was probably a 2×4 strut in the way etc. Now have localized areas that are 1/4″ or more too high.
What is the best tool to grind these down?
Would you consider using a rotary hammer with chipper bit?
Thanks
John
Replies
I would not use a chipping hammer. You won't be happy with the results, and likely have to go back and patch the area. The best way to do it is with a diamond attachment on a grinder meant for honing/smoothing concrete floors. These can be messy, a shop-vac and a dust mask will go a long way here. You can look around and see what your options are but your best options are honing/polishing "pads" that you can find from 20-150 bucks depending on grit, brand etc. These will fit on a standard grinder and make quick work of your problem. Hope this helps, and leave the chipping hammer out of it :b
Robert Griffin, Owner
Katy Custom Kitchen and Bath
http://www.katycustom.com
Mason wheel?
One guy i talked to said i should use a "mason wheel" in an angle grinder. He said those wheels are about 1/4" thick and have some green marking on them to indicate they are for masonry.
Would the diamond attachment (wheel, cup?) be more efficient? I don't want to spend two days grinding high spots!
Thanks
John
John
Where's the guy that created the problem?
Yes, top of wall where plate will rest. No asthetic or dust concerns. I want it reasonably smooth and level so the floor framing and deck are too. Also want a decent sill seal here.
John
Buy a diamond cup wheel for your angle grinder. This will make short work of it. It will also produce copious amounts of dust unless you keep it flooded with water. I'd use a gfi outlet, have a helper handle the hose, and grind away. The diamond wheels are not expensive in the great scheme of things. Masonry wheels are a cheap, but slow, alternative.
I would think about doing it as if you were cutting a notch in a board. Using an old circular saw, you could mount a diamond blade. On the area you need to knock down, clamp a 2x board down on the level on each sid of the problem area, make the top edge flush with the level correct sections. This is your guide fence.
Make a sled using 1x material, the top piece goes over the wall, and two down pices keep the sled square to the outside guide fence. Put a 1x1 rectangle in each corner to lift up your sled 3/4" from the top of the material you are cutting.
Your sled will provide the correct depth of cut. Line the blade up flat to the correct height concrete first, then move your sled along so you can make cross cuts through the high section. Knock those out with a hammer, then you can smooth out the area by moving the sled and blade sideways.
Or just notch the bottom of the plate.
I still think the diamond attachment for an angle grinder is your best bet. I don't use alot of these but the comment suggesting a helper with a water hose sounds right on point, the dust is pretty epic, but it would be a very fast job. You could also try to shave the tops with a diamond blade on a skil saw and a steady hand as another person suggested. Though for the cost it wouldn't be worth it unless you have already have a diamond circular setup, as most of us probably do for concrete, hardi, etc. The cups are cheap and last a bit, especially when used wet. I'm not sure why anyone would recommend notching the bottom of plate. Creating a second problem is not a solution worth using imo.
Robert Griffin, Owner
Katy Custom Kitchen and Bath
http://www.katycustom.com
Yeah, but I can't think of a way to easily do that cut. Maybe with a horizontal router and a 4" bit? BAHAHAHAHA! I just thought of the horror show I would make of that setup. It would make a Zombie movie look like Disney.
Diamond Wheel is your best friend
xxPaulCPxx wrote:
I would think about doing it as if you were cutting a notch in a board. Using an old circular saw, you could mount a diamond blade. On the area you need to knock down, clamp a 2x board down on the level on each sid of the problem area, make the top edge flush with the level correct sections. This is your guide fence.
Make a sled using 1x material, the top piece goes over the wall, and two down pices keep the sled square to the outside guide fence. Put a 1x1 rectangle in each corner to lift up your sled 3/4" from the top of the material you are cutting.
Your sled will provide the correct depth of cut. Line the blade up flat to the correct height concrete first, then move your sled along so you can make cross cuts through the high section. Knock those out with a hammer, then you can smooth out the area by moving the sled and blade sideways.
The above quote is the best advice in my opinion. I would only suggest a diamond cup to smooth the wall after knocking the chips out. A good place the find deals on diamond wheels and blades are at tool rental stores - at least in Alberta. Some of the bigger shops will get them bulk and pass on the deal to their clients. The diamond cup wheel will outlast your obsession with a level sill (level IS good).
To relieve dust, use a pump sprayer and you direct it at the diamond wheel. The guy who messed up the pour operates the saw.
Fresh concrete?
A cheap hatchet, have at it.
Cheap diamond blade in a 4" grinder. How many spots to fix?
Joe H
Definitely a diamond cup for a big grinder - these come in different grits so get the coarsest one you can find - seems like the last 7" diamond cup I bought was $75 or so. Forget about masonary grinding wheels - they aren't agressive enough.
Many times it's easier to use the cup wheel to smooth off any small high points then use an electric hand plane to take some material off the first sill plate for a true flat surface.
diamond cup worked like a charm
....ended up using a 5" segmental diamond cup. Took off all the high spots on 140' of 8" wall in 3 hours. Some high spots 1/2" (localized). A little water kept the dust reasonable.
Thanks to all who replied.
John
Could you not just take your hammer and beat the high spots down while the concrete is still green? If its that bad, I'd have the concrete guys come back with a grinder.
grinding foundation
These are all good suggestions.I have had success grinding "lumpy" foundations.Why not thake the simple approch and scribe the sill. It is only 1/4" +/- . Very easy on a 2x6 sill,and it does not have to be pretty. If it doesn't fit perfectly and the sill seal won't take up the space, simply caulk it !
grinding foundation
These are all good suggestions.I have had success grinding "lumpy" foundations.Why not thake the simple approch and scribe the sill. It is only 1/4" +/- . Very easy on a 2x6 sill,and it does not have to be pretty. If it doesn't fit perfectly and the sill seal won't take up the space, simply caulk it !
grinding foundation
These are all good suggestions.I have had success grinding "lumpy" foundations.Why not thake the simple approch and scribe the sill. It is only 1/4" +/- . Very easy on a 2x6 sill,and it does not have to be pretty. If it doesn't fit perfectly and the sill seal won't take up the space, simply caulk it !
Grinding concrete down to level is about the least efficient method of leveling concrete, the best way is to place forms at the correct elevation, then screed with a screed board, which can be a 2x4 (make sure it is dead straight), or a steel angle.
modular rental forms....
Around here you typically rent your wall forms. They come in several heights but never the one you need. Consequently you end up screeding to a 1x2 level strip that is nailed to the inside of the form at the right elevation - and down as much as 12" inside the forms. With all the 2x4 struts and ties access is less than ideal.
Its a pain and I don't begrudge the finisher for the few spots that are rough.
John
obviously we want to get it right the first time.The OP has a issue with a finished foundation!