Raising a Cinder Block Wall

[mekehret]

I am planning to raise an existing cinder block wall. I have no experience doing brick work of any type. The wall I am raising is made out of 4x8x16 cinder blocks which have tongue and groove ends. Approximately every 10' there are pillars made of 8x8x16 H blocks. The existing wall ranges from 50 to 55 inches in height. I plan to raise the wall by two rows, which will essentially make the maximum new height 6'. I have contacted the builder of the original wall and they have verified that the footer was designed to support up to 9 rows of blocks (above ground). I will be taking the wall from 6.5 visible to 8.5 visible.
I have a couple of questions:

1) I didn't build the original wall and am not sure if there are vertical sections of rebar anywhere in the wall. I am assuming that the pillars every 10' have vertical rebar, but am not sure. Where should vertical rebar be located in the existing wall?

2) As I raise the wall, do I need to place rebar between the pillars?

3) The middle section of the H block pillars has been filled with cement. Should I drill into that and place vertical rebar? If so, how deep should I drill? How many pieces of rebar should I use?

4) What type of mortar should I be using for the wall? Should I use something other than mortar to fill the H blocks?

5) Should I be filling the open sections in the 4x8x16 blocks with mortar or cement?

6) The top row of 4x8x16 is made of the solid top block. Can I just add block on top of that or should I remove the row of solid top block first?

7) The pillars are capped with a 2x8x16 cap block. I would like to reuse these if possible. Is there a good way to remove the existing mortar from these blocks?

8) Is there a good how to book or pdf on building block walls of this sort?

Any help would be greatly appreciated.
Thanks in advance,
Matt

[Rich]

This is a pretty lengthy answer so when I get a little more time I'll get back to you.

[Rich]

1) I didn't build the original wall and am not sure if there are vertical sections of rebar anywhere in the wall. I am assuming that the pillars every 10' have vertical rebar, but am not sure. Where should vertical rebar be located in the existing wall?

A1) As you explained below the top row is solid so I assume an upside down bond beam. If you measure from each end of each block the vertical rebar should be 4" inboard of each edge.

2) As I raise the wall, do I need to place rebar between the pillars?

A2) With only putting 2 more rows on I would say the vertical rebar would be better.

3) The middle section of the H block pillars has been filled with cement. Should I drill into that and place vertical rebar? If so, how deep should I drill? How many pieces of rebar should I use?

A3) If you drill 12 times the thickness of the rebar you should be fine. So using #4 rebar would be 6". If you decide to put vertical rebar in - go every 4' - no vertical rebar go with 2'.

4) What type of mortar should I be using for the wall? Should I use something other than mortar to fill the H blocks?

A4) Mortar / grout would be fine for fill.

5) Should I be filling the open sections in the 4x8x16 blocks with mortar or cement?

A5) Mortar would be better and easier.

6) The top row of 4x8x16 is made of the solid top block. Can I just add block on top of that or should I remove the row of solid top block first?

A6) It depends on if you want to do the work of removing it.. :D Either way I think you would be fine. If you leave it make sure and drill some vertical dowels into it.

7) The pillars are capped with a 2x8x16 cap block. I would like to reuse these if possible. Is there a good way to remove the existing mortar from these blocks?

A7) Hammer and Masonry Chisel. Try and find a dead blow hammer - one shot and it should (fingers crossed) do it.

8) Is there a good how to book or pdf on building block walls of this sort?

A8) Do a search on Amazon.com or Google.com

Hopefully that helps.

[mekehret]

Thanks for the advice! I hope to begin work this weekend, but probably won't finish for several weekends. I will try to post the results and lessons learned once the project is complete.
Matt

[Rich]

That would be great. BTW - Welcome to the forum.