Old Multi-Wythe Brick House 1

[kmart30]

Looked at a possible project of an addition to an old 2 story multi-Wythe hollow brick home with a wood floor and roof. It’s a simple rectangle structure with a hip roof. Architect wants to demo one side of the house and attach a small 2 story addition to it. The addition will be wood with conventional framing and an overframed roof to tie into the existing. There will be a new wood wall in the same location as the old exterior brick wall with some openings that extend into the new addition (same width as house)

There is an exception in the code for additions to single family homes regarding the existing LFRS but just not sure on how to approach this one. Design the new exterior wood wall to take the shear from the old brick wall? Come up with some new steel or CMU in the location of the old brick wall to keep stability? Both? Stop trying to create problems out of 100-year-old structures???

 

[r13]

Removing a structural wall changes the load path/structural property, and depends on your later design, the remaining structural elements of the existing building may experience stresses at a level much different than it was designed for. It is doable, just a bit of tricky to work on an old house.

 

[phamENG]

Since you're keeping the existing roof as is and just overframing into it, I would try to keep the load path where it is and introduce something to take the load that wall was carrying. Unless the old roof was replaced with modern sheathing materials, you're going to have an interesting time tying the roof diaphragm of your new addition to the old 1"x10" potentially gapped roof boards of the existing construction.

It's also important to remember that old houses like that don't always behave as we might expect a new house to behave. The only way wood got tied to brick back then was by embedding the wood in the brick - so it's either held there by compression and friction or it rotted away 50 years ago and the magic of unaccountable redundancy is keeping everything in place (for now). I've had old masonry structures like that where the only way I could make the stresses in the mortar joints make sense was to consider them as a sort of two way system of strips between windows spanning both from foundation to floor/roof and horizontally from wall to wall.

 

[kmart30]

Yes the new wall that is replacing the old wall is supporting the existing roof under the overframing which will take shear and will be designed accordingly. Getting a good connection from existing old hollow brick is tricky as well. I know hilti has some good products(HY-270) for this but I am not sold on attaching to the end of old brick like this. Was thinking a cast in place column where needed....

 

[r13]

I've a suggestion that not necessarily perfect, or work out for your situation, but could eliminate some headache in removing the entire existing wall. How above remove a few layers of the old brick and provide a bond beam to accept the new roof, if possible.

 

[kmart30]

Here is a good picture of what they have....

 

[JAE]

That isn't brick - it looks like structural clay tile.

 

[phamENG]

JAE's right. Similar concept, but different behavior. I'm afraid I don't have experience with that - it was used in my neck of the woods in some composite floor systems, but around here everyone loved their solid brick too much to try it.

 

[r13]

Yes, it is clay brick. You may find more information on this supplier. Link

 

[kmart30]

welp....that changes this project a bit.

 

[phamENG]

retired - definitely not brick. As I said, they are similar but not the same. Even has it's own ASTM, though I'm not sure how available it is (ASTM C34-12, Standard Spec. for Structural Clay Load-Bearing Wall Tile). ACI 530 mentions them a few times (can't use them for a seismic force resisting system for cat C or higher).

Here's a website with some basics:

[URL unfurl="true"]https://historicbldgs.com/terra_cotta.htm[/url]

 

[phamENG]

Found a 1944 national building code that lays out requirements for structural clay tile:

[URL unfurl="true"]https://www.govinfo.gov/content/pkg/GOVPUB-C13-9323df3b0f162a1e77a6f262193b55c7/pdf/GOVPUB-C13-9323df3b0f162a1e77a6f262193b55c7.pdf[/url]

 

[r13]

I don't want to argue, but isn't old brick (non-concrete base) made of clay too? It's just a name, such as kitchen tile, bath tile, all share the same name but different shape.

 

[phamENG]

The terra-cotta pots on my front porch are also made of clay, but I don't expect them to behave like structural brick masonry or even face brick.

Similar to how we design concrete masonry differently than we would a plain concrete wall poured from the same mix the CMU is made of. Just because it has the same base material doesn't mean it will behave the same way. Consequently, we shouldn't design it the same way and should be cautious in our terminology.

 

[r13]

I didn't make up the name. The supplier did.

Historic Series brings the vibrant hues of orange and yellow to these classic clay bricks, adding brilliance to any exterior. Suitable for both commercial and residential use, the decorative bricks feature rounded edges and soft textures, offering traditional old world charm.

 

[JAE]

retired13 - not sure I want to make engineering classification/design decisions based on a brick manufacturer's sales/marketing person's use of happy talk.

 

[r13]

Actually the name "tile" to me is kind of confusing, besides tiles addressed above, many of the roofs around the world are still covered by clay roof tile - another type of flat tile (with minor curvature). To me, a tile is a solid flat clay material with thickness much less than width and length, usually used as facing element that has no structural significance. On the other hand, a clay brick is made of clay with thickness at about one half of its width, it can be made solid or hollow (as shown on the picture), and is a building element that carries load through its structural property.

Either way, the OP has a hollow wall with clay material, whether it is called tile or brick, the important thing is where to locate material property, maybe ASTM, or maybe give the brick manufacturer's sales/marketing person a call to find out.

 

[dhengr]

Kmart30:
Most people who have a modicum of structural engineering knowledge will describe and draw a sketch of two very different building products when they hear the terms clay brick and clay tile. I suppose anyone can call them anything they want, just because they are both made of clay, unless of course, they wish to be understood by the bldg. community at large. And, anyone who doesn’t know/recognize the differences and how they work differently, probably shouldn’t be pretending to be doing structural engineering on a bldg. like this.

I would leave the existing ext. clay tile wall in place and figure out how to cut a few new door openings and the like into it, and frame and reinforce them appropriately. I would infill any openings (windows, etc.) which are not to be used with the new addition. At the very least, I would want to save a 4’ or 5’ return at the two corners on this wall plane. This provides some important integral support for the two adjacent perpendicular ext. walls, and assumes that the existing bldg. is generally in good enough condition to warrant this. While this may not be sufficient, I would make the argument that the bldg. has withstood the test of time, again, good condition warranting this; citing past max. winds, etc. in the range of current code reqr,mts., etc. With a major addition or remodel, the AHJ may reqr. you to upgrade structural, mech. and elec. to meet current codes. The two structures, the existing clay tile and the new wood frame will act quite differently w.r.t. lateral loads and the detailing at the joint btwn. them should account for these differences in stiffness. I would only add new loads to the existing bldg. with great care and considerable engineering consideration of how to do this.

 

[r13]

dhengr,

I don't need to pretend, since nothing to be shied about. Yes, residential building in general is not my area of practice, so in nowhere I will/have used authoritative language, but expressions of my understanding at large. Thanks for enlighten me on the "community at large" situation though.

 

[masonrygeek]

As a masonry guy, I can't let this go too far without clarification (although it doesn't exactly answer the original question).

clay brick - usually modular size (3 5/8" wide x 2 1/4" x 7 5/8") solid units or small cores; ASTM C216 or C652; for older buildings used in multi-wythe mass walls

clay tile - clay based, but more/larger hollow spaces, also larger size; typically weaker than clay brick; cells (holes usually laid vertically although in this project they are laid horizontal); ASTM C34, C56 C212; popular in 1920s-1950s; only one or two manufacturers left (Superior Clay Products (OH), Elgin Butler (TX)); common terms that obscure what this is: SGFT (structural glazed facing tile); speed tile (a particular brand); clay block; loadbearing tile; non-loadbearing tile

ceramic tile - the kind you put in your kitchen or in subways; thin (1/4" thick) and many sizes - 1"x1", 2"x2", 4"x4", 12"x24", etc.; a fired product with clay being ground very fine compared to clay brick or clay tile; applied to walls, not structural

concrete block - made of concrete (not fired like the others); took the place of clay tile in the 1940s and 1950s hollow spaces like clay tile (from the photo uploaded it looks like concrete block directly below the opening that was made in the wall - you can tell by looking at the aggregate)

You can find info on clay tile at places like the Building Technology Heritage Library (

https://archive.org/details/buildingtechnologyheritagelibrary?and[]=clay+tile&sin=&sort=&page=2).

This is showing all the publications dealing with structural clay tile. "Brick and Tile Engineering" (or if you can find it "Tile Engineering") is a great resource for typical strengths and other properties.