I have an upcoming project and I could use some advice. There is a six foot cement block wall, eight inches thick, slightly over sixty feet long. The top of the wall is flat. On this top flat surface I am going to install a redwood trellis. My plan is to core an approx. 2″ diameter hole, ten inches deep and set a square steel pipe in non-shrink cement grout. I will have pre-drilled holes in the steel pipe to receive bolts… so I will be able to bolt on redwood 2 X 4 posts to either side of the pipe… then I can frame in the trellis itself and attach to the bolted 2 X 4’s.
My question is how to best approach the coring. I can rent a coring machine with a diamond coring bit. But I’ve never used one and I’ll be perched up on that wall. My worry is that it will bind (like the holesaw I’m familiar with) and the machine and I will descend rather quickly to a bad end.
I could also rent a big rotary hammer and either plow through with a giant bit or do perimeter drilling and open up a hole that way. But using a rotary hammer makes me worry about blowing the blocks apart, which would be really bad.
I could use your thoughts. I will have to drill 17 holes. Thanks.
Replies
I would guess that any sideways forces on your trellis (like kids playing) will pull out the top cap block where you have them imbedded.
And then, you'll find the wall itself to be hollow cores.
If you insist on doing this, may I suggest removing the top cap block whereever you want to place a post, and 1, be real sure of the placement of your post, 2, core out the hole while the block is on the ground, 3, drop a #4 rebar (long enuff to go up into the cap block) into the wall's hollow and grout (using a ceement mixture) the hole full, then put your capstone back in place and push your post in position. Mortar everything back to prettiness.
hire it out, that core bit is $400
And the job cost itself is like only $50. Really cheep.
Far better than doing it yourself.
Hmmmm... I always get a little worried whenever someone says, "If you insist on doing this..." Is the underlying concept of how this trellis will be built... a lousy one? The only other way I could think of would have been to install posts on the side of the block wall. Somehow I just couldn't imagine that would look good.
you can do this. the core drill is made to be fastened to the wall with anchors that you drill and put in each time. a little water and your good to go be patient and no kick back slow is the key. once again no problem. and that many holes no way are you going to get them foe $50 bucks as some one mentioned.
Thank you for the encouragement! I'm curious as to the fastener of your choice -- what would you use to 'bolt' the coring machine to the top of the wall? Thanks again.
we use a "red head" its an exspanding bolt 1/2 inch diameter.
all the guys I've seen do it around here use the lead exspansion so they can get them back out but then the lead is no longer usable but you should be able to reuse the bolt.