Author Topic: Tying new block to old block  (Read 2500 times)

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Offline Patrick

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Tying new block to old block
« on: January 01, 2014, 05:46:16 AM »
I'm looking for best practices here I plan on adding an 18x18 addition onto my 28' wall I want to come strait off the corner which is solid filled with concrete and I'm hoping to hit another solid filled section on the other end (Blocks where filled every 32" approx) My top course is also solid filled I will tie into the footing with rebar and was thinking of epoxying studs into the old block everyother course and using a 90 degree piece of stainless bolt that to the wall and have a 5/8 rebar go through the steel in the first cavity of the block which would be tied into the footing then tie in the bond course and fill it all in with concrete. Or should I just epoxy rebar everyother course and put in 90's at the ends of the rebar at random lengths tying into my verticals? I have also read about bolting in plates on the exterior of the wall. Im looking for any tried and true meathods here none of my books go into this very well.I am also wondering about stripping the waterproofing off I used a rubberized coating I was thinking of trying watered down muratic acid. And would it be good practice to use a bonding agent afterwards? This is all standard block construction using 12" block with a 12"x24" footing.

Offline Redoverfarm

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Re: Tying new block to old block
« Reply #1 on: January 01, 2014, 06:18:58 AM »
If it were mine I would just use #5 rebar studs epoxied into the old wall @ the mortar joint and equal distance into the new wall mortar joints. The mortared joint in the old block by itself is probably not strong enough but the filled web should be.  You can chip out the end of the new block (top and bottom of that course) to allow the rebar to set into the mortar joint which will not interfer with you mortar joint bond.  That can be done at every other joint.  Then fill that end cavity with mortar or concrete.  To aid in uplift you can pin the footer and allow the rebar to come up to tie to the wall pins.  If you footing is solid and the blocks are laid plumb there should not be any lateral pull and is basicly just for alignment.

You could use a plate jointer which basicly is bolted (wedge bolts) to the existing wall ( assume corner block) with the 90 deg short leg and the longer portion is laid in the new wall mortar joint. Being that you will probably be using a line block there is sufficent room in the end of the block to accomidate the nut & washer. 
« Last Edit: January 01, 2014, 07:33:30 AM by Redoverfarm »

Offline Patrick

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Re: Tying new block to old block
« Reply #2 on: January 01, 2014, 10:40:13 AM »
thanks,  Would you bend the ends of the rebar at all or just keep them strait? if I go this route I think I will tie the stubs to the first vertical then. And yes I used 12" corner blocks and everything was filled about 2' from the actual corner and If I end up hitting a hallow row on the other side can I do the same thing with the rebar and fill the cavity with cement after its all done or should I do something different?

Offline Redoverfarm

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Re: Tying new block to old block
« Reply #3 on: January 01, 2014, 01:03:31 PM »
thanks,  Would you bend the ends of the rebar at all or just keep them strait? if I go this route I think I will tie the stubs to the first vertical then. And yes I used 12" corner blocks and everything was filled about 2' from the actual corner and If I end up hitting a hallow row on the other side can I do the same thing with the rebar and fill the cavity with cement after its all done or should I do something different?

Yes you can. Just remember that the short leg of the "L" has to go in the cavity of the block so it cannot be that long of an "L" unless you extend it upwards and lay your block over it.  Ideally figure the portion that goes back into the block to come out to midways of the cavity.  If you want more into the old block then it will have to be inserted upside down bottomed out then rotating it 180 deg to get the short leg down into the cavity (5-1/8"W for 8" block and 8-1/2" for 12" block.  What I am saying is if you are using 8" block the short leg cannot be more than approximately 2" for 8" block and about 4" for 12" block.  Of course you could off center it to gain a little more length on the short leg.   

Offline Patrick

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Re: Tying new block to old block
« Reply #4 on: January 02, 2014, 04:24:14 AM »
Thank you, thats very helpful I understand exactly what your saying I think this will be the meathod I will use.