Attaching Brick to Block

[ron9876]

Don't have much experience with brick and I am working on a renovation/addition to a very old house. It has a brick veneer over 8" block. We are matching that detail. The brick veneer extends about 4 feet up the wall. Is it enough to mortar the brick to the wall or is joint reinforcement required? High winds and no seismic.

 

[SLTA]

8" block with brick veneer on a very old house? How old is very old? That is a more modern version of construction. Very old, even as recent as 1930s, would have mass masonry, ie solid brick.

I'd do the new part like new construction, as much as possible, with a gap and brick ties. Try to give the brick and CMU room to change size without affecting the other or you might get cracking issues from thermal differences and growth vs shrinkage differences.

With the existing part, if it's working, don't monkey with it.

 

[MiketheEngineer]

Don't forget some weep holes

 

[ron9876]

It was built in 1944. The original drawings, they are things of beauty even if they have limited information, show the brick as a veneer. I am in South Florida and we there isn't much brick in this area.

We don't have the thermal expansion problems here that exist in other climates. The gap and weepholes seem like a lot of effort for brick that is only a veneer that is about 3'-4' up the wall.

 

[ToadJones]

I second gap & ties.

be sure to have weep holes & flashing.
Brick is porous.
Might want to tar the block prior to bricking.
Do not fully mortar the brick to the block.
Brick breaths.

wind driven rains will penetrate the brick.
It has happened on my own house.
If there is no flashing or weeps, the driven rain can easily saturate the brick and wind up in the voids of the block.

I'd add that the brick should be sealed with a silicon sealer after it is install and mortar is cured.
Brick is not even close to waterproof in and of itself.

 

[concretemasonry]

The first problem that may come up with matching the brick (size, texture and color), but that is not a structural problem.

Not all brick are porous and some just will not absorb enough moisture to get a good bond. Many of the older brick. (especially from he older suppliers)from the eastern U.S. are soft and porous, while others are extremely hard, but can vary because of the appearance and architectural effect chosen.

It sounds like you have a block wall with a minimal cavity (possibly open) and possibly could be the brick just set on a footing and laid up along with the brick using mortar between the 2 materials. You MUST determine the actual construction to determine the attachment method.

Even if it is block and brick with mortar slushed between the two using brick ties is now necessary under most codes. If it is a true brick/block veneer and traditional 2" gap for a cavity wall (not likely), the wall will be much thicker and the total wall thickness, so then actual wall construction of the existing adjacent walls will dictate.

If the exterior bond patterns on the exterior indicate the possibility of some brick being laid as ties at 90 degres to the face (usually every 3 or 4 courses) it could be a bonded wall and could be considered a 12" masonry wall.

Structurally, a brick/block wall with slushed ot full collar joints is not considered any different than a 8" wall. If it is a real cavity wall, there are many types of hardware available to maintain continuity and the air space, but that will not quality structurally as anything other than an 8" block wall since the attachment methods do not have the shear strength to make both wythes act together structurally. For a real cavity wall weeps are always recommended including flashing to divert any leakage outward.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[ron9876]

Yes what I need to do is add brick veneer for a portion of the height of the 8" block wall. And it will start from the footing. The original drawings show what looks like the brick placed tight against block.

 

[concretemasonry]

It is good you have the drawings. Just go out and verify the actual wall construction and details of the adjacent walls to maintain continuity.

If it was 1944 construction in Florida, there is no guarantee the the structure was built strictly according to drawings with limited information. There must have been some professional involved in the design and drawings, but no guarntee as to what is now there.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[ron9876]

Thanks for the input.

 

[Ron]

ron9876....the gap is for waterproofing and vapor diffusion. It MUST be in there, particularly in your area. Brick is not waterproof. Mortar is not waterproof. Brick and mortar will expand and contract thermally and with moisture changes...that's one important reason for not mortaring them together.

Use this sequence:

1. Waterproof the block masonry. I prefer an asphaltic mastic.
2. Provide thru-wall flashing at the bottom of the brick and all penetrations.
3. Provide 2" gap between veneer and wall.
4. Install brick using brick ties to connect to wall. Make sure mortar gets cleaned from gap.
5. Provide weep holes in mortar at the thru-wall flashings. Use cotton-core rope in weeps to allow wicking and weeping. Do not use synthetic rope...it will not allow wicking or weeping.

Weeps can be formed in mortar by using small diameter pipe, but better to use rope and leave in place (ever tried to push a rope in a hole?). Typically 1/2" dia. rope is used. Rope also keeps insects and small varmints out.

 

[concretemasonry]

Ron -

This is a minor addition to and older home and is only for a portion of the height of a residentisaal wall and must match the existing apperance. Increasing the gap to over 2" will not make it work, although 6" block are a possibility because the loading would not be a structural problem.

I can't really grasp the statement that the brick and mortar should not be mortared together.

Some brick (which must match the existing) can be very very hard and non-absorbant because the ASTM standards onlt give maximums and not a specific range of properties.

Also, brick has a long term expansion and the portion of a home wall is not enough to be a factor since most codes require soft joints at 2 or 3 stories and the flexible wall ties and "eye and pintel" cavity wall ties will accomodate the long term effects and minimize the thermal transmission.

I have seen many problems with and asphalt emulsion appied too thickly where it became a second vapor barrier and not a vague "vapor diffusor".

Granted, the brick and block construction is the "Cadillac" of masonry walls when a 2" gap is provided, but the wall cross-section is not always possible on an addition. Water and vapor travel in all directions.

There are many acceptible combinations of using brick and block, connection of wythes as listed in most references and standards. Full collar joints are acceptible. If it was up to me, on new construction it would be 6" lightweight block 2"void/rigid insulation space with both weeps AND vents.

Dick

On a residential addition, the call is really up to the architect as far as details and appearance.

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[Ron]

Dick...my statement was not very clear on the mortaring. I was referring to the OP's statement about mortaring the brick and block together. That would not allow an air space, so wouldn't be a good thing.

I agree that some old brick can be very hard; however, the OP is in South Florida. I've done several petrographic examinations of brick in various parts of Florida on old brick and it is almost invariably fired hard for an outside "crust" and much softer in the interior. Small fissures develop in the hard crust allowing moisture migration. Further, even if the brick will resist moisture, the mortar will not.

I'm not a great fan of vapor diffusion theory in building walls. Vapor diffusion tests and calculations assume a steady-state condition. That does not occur in walls.

The asphaltic material should not constitute a second vapor barrier. I agree that it would cause problems if constructed as such; however, the exterior wall surface is not a barrier, so it's OK if the asphaltic layer is a barrier. The vapor drive for his building will be inward.