Tag Archive: Forensic/Foundation and Structural Repair Engineeringc

This (Really Surprising) Old House

View of house from front

Our company does a lot of structural condition assessments of residences, oftentimes for Architects when there is a planned major renovation of an old house.  The City of Atlanta requires an engineer to evaluate the foundations of old homes if a second story is proposed, because there are often problems with the existing foundations.  This house was at first unremarkable, it was an old home in the west side of Atlanta, and was a fairly standard small home built in the 1920’s for working class people that had employment in the cotton mills and factories that once dotted the City.  However, this one had a surprise.  Let’s look at it:

House view from side.

House view from side.

View of house from front

View of house from front

It was just what we call a “shotgun shack”, it was an old duplex that had been subdivided into apartments as the neighborhood got poorer.  I was surprised though when I looked around the side20170512_115649

Notice the subwall is stone – that was not typical of these type of houses.  Usually they didn’t have subwalls, they had brick piers and were open underneath. You usually see concrete block that was placed around the brick piers at a later date to close in under the house and add some space for storage and usually a washing machine.  Also, what was the deal with the blocked up window? Around back  the subwall changed to block, which was odd:

Block placed at the back of the house.

Block placed at the back of the house.

I thought the whole thing was rather unusual, but the answer came when I went into the basement.  I found this:

Doorway to old house.

Doorway to old house.

The house had been built on top of an older stone house!  The stone house underneath has to date back to the mid 1800’s.  It’s rare to find such things around here, most of the older homes were built of timber, which is long gone.  Apparently when they built the shotgun house, there was an old house already on site, and the builder just built on top.  Here’s some more photos:

Interior of older house - note the old window that was blocked in.

Interior of older house – note the old window that was blocked in.  Very impressive stone masonry around the windows.

The front corner - note the newer stone work - it is under a fireplace.  Also, we see a window blocked in.

The front corner – note the newer stone work – it is under a fireplace. Also, we see a window blocked in.

Old timber used to support first floor - this was also salvaged from even older buildings, it is rough sawn.

Old timber used to support first floor – this was also salvaged from even older buildings, it is rough -sawn.

Another view of the recycled timber.  The workmanship here is very poor, unlike the workmanship on the original stone house.

Another view of the recycled timber. The workmanship here is very poor, unlike the workmanship on the original stone house.  The builder simply stacked stone and set the timbers that he salvaged on top.

I have seen the older homes containing salvaged timber, that is rather common.  Reusing timber from old houses or barns that were torn down would have made sense to the builder.  The cost of materials vs. labor probably was more in favor of using the labor and trying to save on materials.  Hopefully the investor that bought the house and the Architect will make use of the old house in the basement and make this a more distinctive house.  This is one of the most interesting homes I’ve ever visited.


Worst Basement Failure Ever

I was going through my photos this morning, and I found this one:

Basement Subwall Failure

This was the subwall in an apartment building.  The building was built back in the 70’s, and was built as part of a development of low income apartments.  If there is ever a case for proper building permitting procedures, these types of apartments in the Atlanta area make it.  In every one of these buildings it appears to me that there was almost no structural engineering, the foundations are often minimal or non-existent, the structure is all wood and all of the members are overspanned, there is no consideration for wind bracing, and as you see here, the subwalls are never strong enough.  I suspect all that was done for the design was a floor layout, some elevations, and that was it.

It also appears that there was no inspection in most of these because the errors in construction are often so extreme that even the most inexperienced building inspector should have caught them.  I always wonder how this worked.  I assume the that at the time the builder submitted the floor plans and elevations, fees were paid, and the permit was issued and that was that.  I suspect there was no inspection at all, or maybe just plumbing and electric.

In this one the subwall was not reinforced properly, the site wasn’t drained properly, and there was not a working underdrain system.  As it rained, water pressure built up against the outside wall and we had a catastrophic collapse.  Fortunately, no one was hurt.  Sad thing is, I have been in one building where a tenant was seriously injured in a failure  – while he was in bed the ceiling collapsed on him.  The ceiling was not nailed to the joists above, it was glued.  In time the glue deteriorated and the ceiling fell loose and seriously injured the person below.

View of Outside – Note the bracing.

The brick wall in in danger of collapse.  By this time the building was condemned and apartments cleared out.  It could have been much worse.  The repairs were done (by replacing the subwall with an engineered one) and the building put back in service.

Every time I go to the old low income apartment buildings I come back away irritated.  The shoddy construction is downright criminal, and shows a total lack of concern for the people that live in the buildings.  The structural problems are many, and in addition the bathrooms are never adequately designed to contain the moisture.  In every building of this type you will find rotted wood all around the bathrooms.  This is not only a danger for the structure, but presents a great place for mold to grow. Also, the windows are usually improperly flashed, so you will see moisture in the structure around the windows – again, causing structural issues and mold.

How was this allowed to happen?  Were the building officials corrupt?  Were they incompetent?  Were they racist (figuring it was primarily minorities that would live in these buildings and thus they didn’t care)?  Was the system itself too lax?  Most likely it was a combination of all.  The sad thing is it hurts people that have no other options in life.

By the way, every time I go to these buildings I talk to a lot of the people that live there.  They don’t seem like the stereo type “welfare recipient/drug dealer/thug” to me.  All of the ones I’ve talked to just seemed like regular people, the kind you’d be happy to have as a neighbor.  They have jobs, families, hopes and dreams.  They just are poor.  That makes it even more irritating to me.

Above all else, it shows how when people don’t do their jobs, it can seriously hurt other people.



At What Point Do You Do Structural Repairs?

A lot of houses I look at have issues with settlement in the foundations and floor slabs.  A lot of times I only recommend cosmetic repairs.  Why is this?  If the house has settled, should you put in piers under your foundations to stabilize it?  Not always, and here’s my rationale:

In many cases I am looking at houses that have been in existence for 20 years or more.  The settlement is often rather minor, and can easily be hidden with simple cosmetic repairs like spackling cracks in the drywall, and filling cracks in exterior mortar.  Let’s say the repairs cost $200.  Usually settlement occurs at its maximum in the first five years or so of the life of the house, from there the settlement never really stops, but proceeds at a much slower rate.  So you would have to do cosmetic repairs on a fairly regular basis – maybe every two years or so.

Generally, it takes at least two foundation piers to repair settlement.  With a budget of about $1,100 a pier, the cost of the repair will be at least $2,200.  How many years will it take for your regular cosmetic repairs to be greater than this cost?  It will take 22 years!  Now with more severe cracking, recent settlement, or if windows and doors are affected, the piers are the best option.  However, in many cases it doesn’t really make economic sense to put out that kind of money.

The other issue is floor slabs.  Often garage slabs are built on soft soil, and they settle over time.  It costs about $6,000 to $8,000 in Atlanta to replace a two car garage floor slab.  If your garage slab has settled about 1/2″ towards the center, and only has minor cracking, do you really want to spend $6,000 to $8,000 for a room that you park your car in and store all your junk?  I wouldn’t.

So, oftentimes I give people the option in my reports – you can do a permanent repair for X amount of dollars and this will happen, or you can cosmetically repair the issue for Y amount of dollars and this other thing will happen.  It often times boils down to economics and personal preferences.


In this case, the cracking is probably due to minor settlement. It would require at least three piers to repair ($3,300), or you could reparge the block every couple of years for the cost of a bag of pre-mixed mortar..

Retaining Wall Failure, Gainesville, GA

Beginning Construction of the Retaining Wall

Client: Residential Customer

This project involved replacing a poorly constructed residential retaining wall.  The failed wall was 24 feet high, and was constructed in 4 foot increments of treated yellow pine timbers to get around permitting requirements (generally walls under 4 feet high don’t have to be permitted in most jurisdictions).  The builder set the walls on a massive pile of uncompacted fill, and buried trash from the subdivision.  The wall started to fail about 10 years after construction, which meant the contractor was nowhere to be found, and the Statute of Limitations had run out.  The wall was showing a wide open tension crack at the top level, which can mean it is beginning to get global failure.  We recommended a geotechnical firm come out and do an investigation.  They couldn’t get a boring rig onto the site, so they did hand auger borings to about 12′ and found poor soil.

We designed three walls made of reinforced concrete to step up to the back yard.  Excavation began, and the contractor encountered a deep trash pit about 15 feet below the ground.  This raised the specter of serious global failure, so we recommended a different geotechnical engineer examine the site, Mr. Robert Turton of Oakhurst Geotechnical.  Mr. Turton has many years of experience with soil engineering, and he performed a slop stability analysis to determine what soil improvements had to be done.  He also monitored removal of poor soil and placement and compaction of fill.  We had to change our wall design to reflect the new profile, and we were on site several times a week.

A year after the new walls were constructed, the 500 year storm hit the area, flooding many areas, and causing many structural collapses.  Our walls remained stable, which we are certain is more than can be said of the original walls.

The original walls as failure was starting.

The Original Wall - you can see cracking in the mulch at the top about two feet from the grass.















A view of the trash pit that we found.

A View of the Trash Pit We Found















Compacting Fill After The Trash Was Removed















Beginning Construction of the Retaining Wall

Would Shipping Container Houses be Safer In Tornadoes?


I’ve been asked this question on my Facebook page, and it is a good question.  I originally wrote about this last spring, and I’m rewriting the post today (October 22, 2011).  The original post said no, but I’m going to change the answer to “yes and no” or let’s say – it depends.

Notice that heavy recliner that was deposited in the middle of the open area



The first thing I noticed is that tornadoes destroy in their own peculiar way.  I’ve seen buildings that have been destroyed by fire, falling trees, windstorms, and exploding bombs.  Each method of destruction leaves its own footprint.

With a fire, you have the charring of the wood, and the worst damage where the fire started.  Falling trees bash in a building where they hit, but the damage is generally localized.  Windstorms push a building over from one side.  Tornadoes are completely different.  Let me make a list:

1.  They tend to destroy worst about 10′ (2M) above the ground – see the photo above.

2.  They destroy from the outside in, like peeling an apple.

3.  They throw things – look at the debris in the picture above.

4.  The force they generate is phenominal.

Here’s another picture:

The building in the above picture was destroyed by pretty much a direct hit.  I think two people died in the tornado that did this, and while I don’t know exactly where it happened, I suspect it was in this block of buildings – the destruction was too extreme.

The problem with a container house is if you get a direct hit, there isn’t much it can do to protect you.  The debris can penetrate right through the windows and doors.  The force is so extreme it’s likely to destroy the building anyway, because you loose a lot of strength when you cut sections of it out.  You are better off with a safe room or basement (because the damage tends to be above ground, I think basements are the best).

However, what if you are on the outskirts of where the tornado hits?  The steel skin can do a much better job of stopping flying missiles than what is typically used in modern home construction – vinyl siding with thin foam sheathing behind it.  It also is likely to resist the higher winds that will hit it than conventional construction.  The first house we designed in Atlanta was unfortunate enough to be in the same neighborhood hit by the Cabbagetown Tornado.  While other houses around it had roof and siding damage, it had no damage whatsoever – although it was not in the direct path of the tornado.  In a direct hit it would have been destroyed.  However, it has a concrete subwall basement, so the owner would have had a refuge in such case and probably would have survived.

So, to modify my original point – container houses are not an adequate shelter for tornadoes in a direct hit, they can provide significant resistance to damage caused by a tornado that passes close by.


The Horror of Termites

Floor Joists Damaged By Termites

I have done structural evaluations on a lot of homes where there was extensive termite damage, but this one I had a some time to do some extra exploration.  I was working on a separate problem in the house, and while there some blistering of paint on a window sill was discovered.  The contractor was asked to pull it up, and SURPRISE!   There was extensive termite damage.

On this one, we had time to do some poking around, and we did a bit of experimentation to see just how well termites can hide from site.  Watch this video:

Notice how well they have concealed themselves?  If you had banged on that piece of timber with a hammer, it would have felt solid.  Also, if you probed it with a sharp object, you probably would have felt anything.  Note, we had to pry in there with a wrecking bar to find the damage, which was extreme.

The termites left a nice shell of preserved wood to protect themselves and hide their presence.  They had no visible mud tunnels, they got in to the wood through the wall, which was backfilled with soil (which is against Code btw, but this was done a long time ago).   In the end, I checked the crawl space by taking a drill and drill holes all around the perimeter.  We found other damaged areas, but fortunately for the homeowner, nothing that needed serious repairs like are being done here.

The worst house I’ve seen is this one (it’s a foreclosure):

Sagging Floor

The joists holding up the floor above are completely destroyed by termites, the floor is sagging under its own weight.  The timber is so thoroughly destroyed that it is the vinyl floor covering holding up the floor.  I discovered this when I walked on it.  Fortunately I was able to run off of the floor before making it collapse.

This house was built in the seventies, and it appears that the roof may have leaked for a long time, which fed the termites moisture.  Here’s a picture underneath:

Floor Joists Damaged By Termites

The photo above is rather confusing to look at because of all the hanging insulation, white mold and rotted wood, but it gives a good indication of the damage to the structure underneath.  Note how grey the subfloor is – it was heavily rotted.

For a house to get to this kind of condition, extreme neglect is required.  I’m not sure how the occupants lived in it.  It was pretty nasty, and I was told it looked worse before the cleanup.  Foreclosures don’t always look this bad, but if you buy one at an auction you don’t get a chance to do a thorough investigation.  I would consider the risk, you wouldn’t have wanted to buy this house at any price.