Reinforcing Old Masonry Building

[bpstruct]

Looking at an old sandstone masonry building (built in 1894). The masonry and "mortar joints" have severely degraded over the years. The back wall is severly cracked throughout. Northwest corner has collapsed. Virtually no roof (giant holes throughout, several localized collapses). Second floor is the same. First floor framing above the basement is even rotten, heavily cracked, and completely gone in some locations. I did a structural inspection on this building two years ago (before the wall collapsed) and recommended demolition. I did this for the city, who did not own the property. I believe there were some legal actions take by the owner to prevent condemnation of the building at the time of the initial inspection. After the wall collapsed, the city stepped in again. I looked at it again, contacted an asbestos abatement demo contractor (there is asbestos in the building), produced demo plans, and obtained a demo bid. We live in a very small town....no options for contractors (the one I contacted is 100 miles from here). The city does not have the money to demo this building and has asked that I explore other options. I see none that I am comfortable with, but I understand the city's position. However, I want to perform my due diligence and explore ideas as requested. Does anyone have a reference they can point me to?

Also, has anyone reinforced a wall like shown in the attachment?

 

[Michel60]

Good morning bpstruct,
How to strengthen and preserve archaic building materials is a bit of an art. I don't have a particular reference for retrofits but I've used "Structural Analysis of Historic Buildings" by J. Stanley Rabun to help better understand some of the original conditions. For structural evaluations of the existing condition there are "guidelines" such as FEMA 304 thru 306 that can help you categorize the structure in terms of it's risk...but it sounds like this might already be apparent.

The detail you provided I'd describe more as an "encapsulation" than a strengthening. Basically it's a couple of layers of reinforced plaster. In its application I'd expect the existing masonry wall to be pretty sound from the start for the approach to be effective. Historic masonry can be rebuilt but care needs to be taken to use compatible materials. Mixing modern portland cement based mortar with old lime based mortar should be avoided.

regards,
Michel

 

[bpstruct]

Well the idea didn't seem great to me...particularly because of how thin the cement was on each side. I found that detail online in an article about strengthening old masonry structures. The end walls of this building are partucularly bad. There is no connection (at least none that I can see - and I can see most of the framing) between those end walls and the framing. If those walls are rebuilt with block and tied to new roof framing, I am concerned about how I would make the connection to the remaining long walls (those aren't in great shape, but not nearly as bad as the end walls). I have found articles that support your position not to mix cement mortar with lime mortar, but none that talk in any detail about why.

 

[dik]

There's a copy of a paper on historic brickwork on slideruleera's website (

http://www.slideruleera.org,

I think) that has some information.

Encapsulating the brickwork as proposed prevents 'wicking' the moisture from the building, and is not a real good idea. It can hasten deterioration. You do, however, have a few choices:

Demolition... easy and likely relatively cheap... building is lost... bad if the structure has some historical significance or Architectural significance.

Renovation... can be costly, more so, the amount of original material you want to keep... also requires an owner...

Restoration... can be more costly and it's a matter of stabilising the structure and undertaking repairs... good for a century type of building and my preference.

Stabilising... the structure can be stabilised until money is available to undertake Renovation or Restoration.

Good Luck... Dik

 

[dik]

It's dot net, not dot org...

Dik

 

[Michel60]

The issue of mixing of new and old materials in masonry is essentially one of stiffness compatibility. Newer materials are much stiffer (numerically higher elastic modulus). As dik mentions this can result in more rapid deterioration of the remaining historic material. For example, if you were to re-point an existing lime mortar wall with portland cement mortar you create hard spots that concentrate the forces in small areas surround by "softer" masonry. This accelerates the deterioration of the softer original material because of the stress concentration.

This brings us back to your question of tying in new masonry to the original, you'd like to keep them separate or provide some measure of resilience in the connecting element between the two.

Connecting floor and roof elements to old masonry can be challenging. Bearing joist/beams on the masonry in pockets and providing a steel through-wall tie with a backing plate on the exterior is most common. Not an attractive solution but effective.

regards,
Michel

 

[shobroco]

There are a lot of things to consider in the building that you are describing, but the first thing is to discard the proposal in your sketch. That is a recipe for a wall that will deteriorate from trapped moisture (especially if you have freezing temperatures) without revealing it until it is at the point of catastrophic failure because you've hidden it. If the town would accept this solution, then the building obviously does not have historic or architectural significance since this would destroy that, so despite my aversion to ever doing this with a good building I would say tear it down. That's the cheapest option and what you're proposing is not saving it anyway. If you do want to save it, this forum is insufficient to teach you about historic masonry, but there is plenty of information out there if you cannot engage some experienced in the field. The US National Parks Service has a good series of bulletins, start here.

http://www.nps.gov/tps/

 

[dik]

shobroco... there are a few of us that can provide him with guidance... he can start with the short paper on Historic Brickwork on

http://www.slideruleera.net

for a bit of info. There's no question that old masonry restoration is a science/art all unto itself and there are lots of 'park' agencies that are there to help.

From the deterioration noted, it appears that a poor quality of mortar was used in the original construction with limited hydraulic properties and over time, these have leached out leaving only the 'sand'... a not uncommon problem with historic brickwork.

The work ahead is detailed and expensive...

Dik

 

[MikeHalloran]

There is a fair amount of 'deconstruction' of wood frame buildings going on in New Orleans, wherein the building is pulled apart carefully, piece by piece, and the lumber is reused, perhaps in shortened form, to construct a new building.

I wonder if you can find a building materials supplier who'd like to obtain an inventory of historical materials for the cost of deconstructing the building and cleaning up the site.





Mike Halloran
Pembroke Pines, FL, USA

 

[bpstruct]

The city is simply wanting a safe solution to the issue. The building actually DOES have historical significance. It is the oldest building downtown and has one of the most unique looks. The walls are already severely deteriorated (collapsed in one location), and that is my dilemma. The city doesn't feel like it can afford the demo (primarily due to the presence of asbestos). The building is such a structural concern on the interior that all of the material is being disposed of as ACM (asbestos containing material). I inspected this building two years ago and recommended demolition then. The city would like an alternative, but I don't really see one that I feel comfortable with. I read the paper referred to above, and have looked at other references. But I'm still left with too many uncertainties.

I appreciate everyones' comments. I think my response to the city is still going to be that it has to be demolished.

 

[dik]

Demolition is forever, earthling...

Dik

 

[MiketheEngineer]

If they can't demo it - mother nature will. Can it be fixed - sure at great expense.

 

[bpstruct]

I hate recommending demolition for these old buildings. I am on our county historical commission and believe in preservation when it is a safe option. But the bottom line is that nobody has the money to repair it (including the city), and it is completely unsafe to sit like it does. Living in a small place like this is great, but there are some real challenges to solving local problems like this....this is not like it is in the city where you have qualified contractors to address problems like this. Even fewer who would be willing to give a price for the work.

 

[shobroco]

Can you tell us where you are & possibly someone close to you with experience in this area can help you? I'm assuming you're not near me, in Southern Ontario, but I do know a few people in the field in far-flung places, & I'm sure there are plenty of others who do as well.

 

[chicopee]

About getting a grant from the Historical preservation society and reconstruct the building to its original form as closely as possible. Preservation of this building should provide much needed jobs to construction workers.

 

[bpstruct]

I am in North Texas. This place is so small that we have only one local contractor that is capable of doing this kind of work. None that are qualified to do the asbestos abatement.

 

[connect2]

You really need to determine the material properties of what you have first, the brick and the mortar, gapping holes and collapsed areas aside. FEMA 356 can help you alot with this. The rehabilitation of URM there's lot's of techniques discussed in FEMA 356 and 547 as well. It is partially an art but at the same time you will find that there has been a lot of research and work going into seismic rehabilitation of URM buildings because there is a lot of them around. Good luck.

 

[ztengguy]

i would have to think that demo the building is cheaper than any labor intensive work such as this.