Need Help On How To Increase The Size Of A Small Opening In My Basement Wall

Reply

  #1  
Old 10-23-11, 02:29 PM
Member
Thread Starter
Join Date: Aug 2009
Location: New York
Posts: 251
Received 0 Votes on 0 Posts
Need Help On How To Increase The Size Of A Small Opening In My Basement Wall

My basement has a small square opening in a cement block wall leading to a crawl space that's under a small addition.

The opening is only 18" x 16" so I would like to make it bigger so it's easier to get in and out of the crawl space for maintenance. I'm only looking to increase the size by 6 or 8 inches both vertically and horizonally.

My question is how can I increase the opening size myself without hiring someone? I read on the internet that I could use a hammer drill with masonry bits. It said to drill closely spaced vertical holes through the block then use a masons/cold chisel with a heavy hammer to chip away sections of the block I want to remove to arrive at the desired size. Will this work? Is there another or easier way?

Would appreciate any comments and suggestions.

Thank you
 
Sponsored Links
  #2  
Old 10-23-11, 05:40 PM
ray2047's Avatar
Member
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
First is there a header and if not is the area load bearing?

I would use a circular saw with a masonry blade to out line the hole. If you can get to the other side I'd do it on both sides. I'd probably use a cheap 7" diamond blade (less then $40) rather then carbide because the carbide get smaller as you cut and you have to keep changing them out to get decent depth. You could also use an angle grinder. You should be able to cut almose all the way through the cell walls. The blocks will break easily along the cuts and you will have a smooth opening.
 
  #3  
Old 10-23-11, 06:35 PM
Member
Thread Starter
Join Date: Aug 2009
Location: New York
Posts: 251
Received 0 Votes on 0 Posts
[QUOTE=ray2047;1900373]First is there a header and if not is the area load bearing?/QUOTE]

The existing hole to the crawl space starts at the very top of my basement wall just under the sill wood plate. Therefore, the top of the opening is in fact the sill plate. So the sill plate in my case actually serves as a header I think?

The opening (18" wide and 16 1/2" high) to the crawl space is at the top and in the middle of a 15 foot long basement wall. As I stated previously, I'm only looking to make the opening a little bigger.

Your suggestion to use a circular saw with a masonry blade sounds like the kind of solution I'm looking for since it might be easier than drilling a series of vertical holes. One question regarding using a circular saw is- do I need to saw completely through the block in order for the block to break apart? I'm asking because the top course of blocks just under the sill plate is 8" wide and the second and third course under it are 10" wide. Will this pose any problem?
 
  #4  
Old 10-23-11, 07:49 PM
ray2047's Avatar
Member
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
do I need to saw completely through the block in order for the block to break apart? I'm
No, and in fact the blade won't go deep enough but it should break along the cut. One reason I suggested cutting both sides was to get a better break. The saw will only cut about 2" and I'm guessing the blocks are 8".
 
  #5  
Old 10-23-11, 09:45 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,196
Received 0 Votes on 0 Posts
An angle grinder with a masonry wheel is your friend. You can use it to knock down any projecting edges of broken concrete block. Also, you may have to fill in a void or 2 with mortar, if your blocks are laid in a standard Dutch-bond (half-block) pattern.
 
  #6  
Old 10-24-11, 03:30 PM
Member
Thread Starter
Join Date: Aug 2009
Location: New York
Posts: 251
Received 0 Votes on 0 Posts
Great suggestions regarding using a circular saw or angle grinder since I have both.

However, I have a few questions.

1. Are we talking about using a fiberglass cutoff wheel designed for cutting masonry or a metal saw blade with slotted reliefs for cutting masonry?

2. Does the saw or angle grinder RPM matter? Is higher rpm better or doesn't it make a difference? I ask because one of my angle grinders operates at 10,000 rpm and my circular saw operates at about 5,000 rpm.

3. Also, will my 4 1/2" angle grinder work ok or is it too small?
 
  #7  
Old 10-24-11, 04:12 PM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,119
Received 2 Votes on 2 Posts
No Pro...but I found out after cutting down a block wall that a single dry cut diamond blade is WAAAAAYYYY better than ten fiber blades, even if it costs twice as much.

I was using a 10K rpm angle grinder....the diamond went through like butter.
 
  #8  
Old 10-24-11, 10:16 PM
ray2047's Avatar
Member
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
Agree on the diamond blade. I bought one for $27 that lasted me for years. As I said in my first post the carbide blades are sacrificial and must be changed often to maintain the depth of cut.
 
  #9  
Old 10-25-11, 06:39 AM
Gunguy45's Avatar
Super Moderator
Join Date: Dec 2007
Location: USA
Posts: 21,119
Received 2 Votes on 2 Posts
The other thing about a diamond blade is you get full depth of cut for a long time. As the fiber blades wear you have to keep going back over cuts with a fresh one to get full depth.
 
  #10  
Old 10-25-11, 04:02 PM
Member
Thread Starter
Join Date: Aug 2009
Location: New York
Posts: 251
Received 0 Votes on 0 Posts
You've all convinced me that a diamond blade is the way to go and I thank you.

I guess the only unanswered question in my mind is whether using a 4 1/2" angle grinder with a diamond blade will do a good job? Or is it too small?
 
  #11  
Old 10-25-11, 04:52 PM
ray2047's Avatar
Member
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
You only need to cut deep enough so when you break it out the break runs true but the deeper you cut the more like it is to run true. I find a circular saw easiest to handle but then the only angle grinder I have is 7". A 4" should work, especially if you cut from both sides.

A couple of Tips: at the horizontal line cut along a mortar line. Mark out your verticals so they are not on a cell wall. After cutting you can fill in the hollows with mortar.
 
  #12  
Old 10-27-11, 03:09 AM
Member
Join Date: Feb 2005
Location: USA
Posts: 1,396
Received 0 Votes on 0 Posts
The 4 1/2 inch angle grinder/diamond blade is a great choice because it's small and easy to work with in tight quarters. Unfortunately it won't cut as deep as a 7 inch or a circular saw.
My main concern would be the dust that this will create. Make SURE to wear a respirator...not a paper dust mask! Also, wear eye protection. The dust, especially on the inside of the space, will be considerable. If any of this work will take place in a finished space, you'll have a LOT of cleanup to do. Be careful and good luck!
 
  #13  
Old 10-28-11, 12:56 PM
Member
Thread Starter
Join Date: Aug 2009
Location: New York
Posts: 251
Received 0 Votes on 0 Posts
First, I want to thank everyone for their recommendation to use a diamond masonry blade for cutting my cement blocks to enlarge the crawl space opening. I bought an inexpensive 4 1/2" diamond blade at harbor freight and it worked wonderfully. Lots of dust.

Now, I have one more question. Although the blocks pretty much broke off on the cut line, there are some jagged edges and protrusions that I'd like to smooth out in order to make the walls of the opening square.

Can I use the inexpensive masonry grinding wheels with my angle grinder to do that? If not, what can I use?

Thanks again for your help.
 
  #14  
Old 10-28-11, 01:28 PM
ray2047's Avatar
Member
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
Can I use the inexpensive masonry grinding wheels with my angle grinder to do that?
Yes. If they are big enough you don't have to even cut all the way through, just score and snap.
 
  #15  
Old 10-28-11, 04:19 PM
Member
Join Date: Feb 2005
Location: USA
Posts: 1,396
Received 0 Votes on 0 Posts
Why not just use the diamond blade again? That's what I do. It works fine for cutting AND grinding.
 
  #16  
Old 10-28-11, 05:20 PM
Member
Thread Starter
Join Date: Aug 2009
Location: New York
Posts: 251
Received 0 Votes on 0 Posts
Originally Posted by Pecos View Post
Why not just use the diamond blade again? That's what I do. It works fine for cutting AND grinding.
I thought it was only for cutting and that you shouldn't put side pressure on it? Not true?
 
  #17  
Old 10-28-11, 05:32 PM
ray2047's Avatar
Member
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
Originally Posted by targa View Post
I thought it was only for cutting and that you shouldn't put side pressure on it? Not true?
That is true.

...............
 
  #18  
Old 10-28-11, 07:58 PM
Member
Join Date: Feb 2005
Location: USA
Posts: 1,396
Received 0 Votes on 0 Posts
It may be true, but I've done it for about 20 years, and even just yesterday. However, to be politically correct I'll say "follow manufacturer's recommendations".
But why can't you "cut" the rough parts off instead of grinding them down?
 
  #19  
Old 10-29-11, 06:40 AM
Member
Thread Starter
Join Date: Aug 2009
Location: New York
Posts: 251
Received 0 Votes on 0 Posts
Originally Posted by Pecos View Post
But why can't you "cut" the rough parts off instead of grinding them down?
In a couple of areas its more of a bulge that I need to grind down to make the side of the opening plumb. That's why I asked about using masonry grinding wheels.

Thanks
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: