mortar question

Posted by George on October 9, 2009, 8:21 am

I'm replacing a lower roof, which abuts a cement-block wall. I need to
flash this joint. In other places, I've cut a slit in the blocks, and
fit the upper flashing into the slit. I can't do that here. Long story
- basically, there's an opening in the blocks that can't be filled with
masonry. The opening can be covered, though.

I'm thinking to run a strip of wood along the wall at the joint. The
upper edge of the wood could be tapered down for a smooth transition to
the block surface. This would cover the opening, and the flashing
would be attached to the wood. I would then need to seal from the block
wall to the upper side of the wood and flashing. I plan to use mortar
for this.

Questions:
1. What cement to use. I've read that acrylic-modified cement has
considerably improved adhesion to wood/metal. Yes? If so, would
something like Quickcrete Concrete Patch (contains vinyl) be a good
choice? Or, would it be better to look for a stucco product?
Or something else?

2. Should I use wire lath over the block-to-wood transition? I guess I
could even nail the lath into the flashing, though that may be one of
those things that works better in your mind's eye than in reality.

Thanks,
G

Posted by DanG on October 9, 2009, 9:38 pm

George, I don't know if I really understand the problem. It
sounds like installing a counter flashing higher on the wall would
be the best solution rather than wood and concrete. Look up
counter flashing, here is one good site that may give you some
good ideas:
http://www.copper.org/Applications/architecture/arch_dhb/flashings_copings/counterflashing.html

Look at detail 2 in the A drawing where they install the
counterflashing in a sawn in reglet. There is another similar in
drawing C.

Another option would be to use a surface counterflash like the
first two shown here:
http://www.wph.com/products_counter.aspx

--
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)
dgriff237@7cox.net

> I'm replacing a lower roof, which abuts a cement-block wall. I
> need to
> flash this joint. In other places, I've cut a slit in the
> blocks, and
> fit the upper flashing into the slit. I can't do that here.
> Long story
> - basically, there's an opening in the blocks that can't be
> filled with
> masonry. The opening can be covered, though.
> I'm thinking to run a strip of wood along the wall at the joint.
> The
> upper edge of the wood could be tapered down for a smooth
> transition to
> the block surface. This would cover the opening, and the
> flashing
> would be attached to the wood. I would then need to seal from
> the block
> wall to the upper side of the wood and flashing. I plan to use
> mortar
> for this.
> Questions:
> 1. What cement to use. I've read that acrylic-modified cement
> has
> considerably improved adhesion to wood/metal. Yes? If so,
> would
> something like Quickcrete Concrete Patch (contains vinyl) be a
> good
> choice? Or, would it be better to look for a stucco product?
> Or something else?
> 2. Should I use wire lath over the block-to-wood transition? I
> guess I
> could even nail the lath into the flashing, though that may be
> one of
> those things that works better in your mind's eye than in
> reality.
> Thanks,
> G

Posted by RicodJour on October 9, 2009, 11:18 pm

> I'm replacing a lower roof, which abuts a cement-block wall. =A0I need to
> flash this joint. =A0In other places, I've cut a slit in the blocks, and
> fit the upper flashing into the slit. =A0I can't do that here. =A0Long st=

ory

> - basically, there's an opening in the blocks that can't be filled with
> masonry. =A0The opening can be covered, though.
> I'm thinking to run a strip of wood along the wall at the joint. =A0The
> upper edge of the wood could be tapered down for a smooth transition to
> the block surface. =A0 This would cover the opening, and the flashing
> would be attached to the wood. =A0I would then need to seal from the bloc=

> wall to the upper side of the wood and flashing. =A0I plan to use mortar
> for this.
> Questions:
> 1. What cement to use. =A0I've read that acrylic-modified cement has
> considerably improved adhesion to wood/metal. =A0Yes? =A0If so, would
> something like Quickcrete Concrete Patch (contains vinyl) be a good
> choice? =A0Or, would it be better to look for a stucco product? =A0
> Or something else?
> 2. Should I use wire lath over the block-to-wood transition? =A0I guess I
> could even nail the lath into the flashing, though that may be one of
> those things that works better in your mind's eye than in reality.

I'd lose the wood and go with proven products...assuming that you
don't want to find out that your detail didn't _quite_ work.

These guys have been around forever and are big in commercial
construction.
http://www.fryreglet.com/details-roof.htm#
Hit up a roofing supply house in your area and ask at the counter what
product they stock and/or would recommend.

R

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