Bonding cinder blocks...

[Printer Mike]

A pine tree fell on top of my boathouse/workshop a few years ago. The force spread the roof joists(not built properly by me) and cracked the block wall at the mortar joints. Using jacks and a come-a-long, the roof and walls were brought back in place, and now it's almost like it never happened. The cracks are visible upon careful inspection. I was wondering if there is anything that could be injected into the thin cracks that might rebond and strenghten the joints.

Thanks for any help/ideas/comments...

 

[G_P]

Perhaps you could find some of the epoxy that is used to bond achors into concrete and use that?

 

[Printer Mike]

Some pics before repairs...

 

[mobetta]

grind out the old mortar and re-tuck point. there is not bond there now, but if you grind/ chisel out that old mortar- a bit at a time, and pack some new mud in there it'll be OK.

 

[chopper103in]

i would remove the roof and then reset/ replace the blocks

if you wanted to make it more solid i would put rebar through the holes in the block and then fill the holes with block fill (a really wet mix of portland and sand

 

[Printer Mike]

Thanks for the info.

The old block buillding was built in the early 70's with a flat roof. Head room was always limited. When I replaced the flat roof with a gable, I didn't use any cross bracing to maximize head room... I thought the block wall would handle the side load. Hard lesson learned.

 

[Ironcrow]

i would remove the roof and then reset/ replace the blocks

if you wanted to make it more solid i would put rebar through the holes in the block and then fill the holes with block fill (a really wet mix of portland and sand

This is what I would do too. Drop a #5 rebar in each cell and will it up with 4000 psi concrete.

And do a scissor truss or collar tie.

 

[Flange]

I didn't use any cross bracing to maximize head room... I thought the block wall would handle the side load. Hard lesson learned.

Cement, concrete and the like is very strong in compression and very weak in tension. By not putting ties in to your roof you imposed a side lead which imposed a load on some of the masonry in a direction which put it in tension.

My opinion is to put some props under the roof , take off those blocks where the joints have failed and re-bed them. You don't actually need to jack the roof up, just support it.

 

[Torque1st]

A good well supported ridge beam would have helped support the load. It may not be possible because of the overhead door.

You could also lag a 2x10 flat up against the rafters near the wall.

Flange has the right idea. Fill the block with rebar and concrete also. Then use fiberglass and epoxy to coat the walls with tensile loads like they do for masonry in earthquake zones.

If you add some cross ties you could jack up the roof and run another course or two of block around one side at a time.

 

[M3Pilot]

Many years ago my brother covered a block barn with some material that looked a bit like stucco. There were several cracked seams between the blocks. It's held up well for 20 years or more. I don't remember what the product was called & can't ask my brother because he's deceased. Wish I could be of further help.

 

[Tink]

I think what M3Pilot is talking about is a product called Surewall. My stepfather used it for a pump house. I that was about 20 years ago also. I believe it it still intact.

 

[Printer Mike]

Thanks again for all the suggestions!

I especially like the idea of adding a course or two of block to remedy the old headroom problem.

 

[Greatbear]

Since the roof has to basically come off, it should not be too much of a deal to take apart the broken courses of block and reset them. While there you can add an extra course or two, as well as rebar the wall and fill the pockets.

 

[REAL HOT SCHITT]

Hi
your best bet is to put into cavity a full height length of reinforcing rod and pour in2 cavity a mix of ready mix....using pea gravel.

2nd option if above no good?...
Grind out mortar joints using masonary disk and blow out dust, dampen blocks to stop dehydration and then repoint using fresh mortar.

Repeat other side. (on outside south face....use a weather joint pointing).

Adhesives do not work from work ive seen.

 

[MScott]

Surewall is a brand of Surface Bonding Cement. It is a mixture of Portland cement, fibreglass fibres and other ingredients that seals and strengthens concrete block walls. I understand that it has been used in the construction of underground homes using dry stacked concrete blocks coated inside and out with the material. The wall then becomes strong and waterproof. IIRC, the Mother Earth News built some underground shelters using this method and material.

 

[johndenver]

I think what M3Pilot is talking about is a product called Surewall. My stepfather used it for a pump house. I that was about 20 years ago also. I believe it it still intact.

20 years and still holding strong?

 

[Tink]

20 years and still holding strong?

If I remember,I'll ask next time I talk to him.

 

[mobetta]

I guess the first question is - Whats your budget?

now you are in the south, with little to no snow load, and that roof design would probably hold up fine for many a year if you just keep the trees of it. adding collar ties up high would help, but it still isnt designed to hold up trees.
if you want/need to go cheeep, grind out the mortar and re-tuck it.

if you have thousands to spend on a boat house, rip the roof off, add 2+ course of block, do core fills where needed, and get some room in attic truss' so you can have a mancave/ sewing studio/ art studio/ woodshop/ kids playhouse/ whatever you need to tell the wife to justify it.

 

[rsanter]

I like the idea of raising the roof at the same time you do the fix.
keep in mind that you do not have to use blocks to raise the wall height, you could add a 2ft wood framed stub wall on top of the blocks and then the roof. I really recoemnd you cross brace/cross tie the roof for the next round.
you could also add some slit windows in the part you add to the walls to bring some light in while having minimal security issue

bob

 

[M3Pilot]

20 years and still holding strong?

Tinks description sounds like the product my brother used and it's still holding up well.

 

[Daniel Dudley]

Surewall is a brand of Surface Bonding Cement. It is a mixture of Portland cement, fibreglass fibres and other ingredients that seals and strengthens concrete block walls. I understand that it has been used in the construction of underground homes using dry stacked concrete blocks coated inside and out with the material. The wall then becomes strong and waterproof. IIRC, the Mother Earth News built some underground shelters using this method and material.

Using this method you are required to rebar and fill block cavities on the corners and at four foot intervals. This will make a strong wall.