Any Building Engineers Out There?

[marko]

I know I'll likely have to get someone down to look at this first-hand but thought I'd run it by our elite crew here first.

I have a 100 year old three car detached garage that is slowwwly settling into the ground at about 1/2 inch a year. (great story on why it is now a two car garage...see photo).

I have no idea what there is for footing but there doesn't seem to be much of anything in the way of a foundation. The inside was hot-topped about 60 years ago which seems to be holding, while the vertical studs sink down.

It is settling back to front to the point where I'll need to cut a few inches off my overhead door this summer in order to get it to close properly (see photo). The roof and walls are in reasonably good shape as are the beams that run around the top of the walls. It's a fairly solid building except for the sinkage.

NOTE: Let me start by saying that I do not want to get that mess back to square; I just want to stop/slow the sinking.

My thought is to place a set of 4X4's, top and bottom in each corner with the top brace angled such to have one end on the top front beam and the other end on the top side beam. Then I'd get those floor jacks and just tighten it up snug without really jacking it.

Any problems with this?

I'm trying to keep it simple and inexpensive. If it's going to run into sinking (pun intended) big money into this, we'll likely just tear it down once it becomes unusable. Frankly I'm just trying to get another 15 years out of it.

Any insight appreciated.

 

[rodi]

I'm not a building engineer... but I'm married to a former architect and have sat in on a lot of conversations involving stuff like this. (Although mostly with retaining walls or houses, rather than garages.)

It seems like part of the problem is lack of proper foundation. Until that is addressed, it seems like you'll continue to have problems. You might need to trench and pour at least some sections of new foundation...

That said - my degree was in engineering of the electrical type... not structural.

 

[Whisper66]

Assuming the entire garage is sinking 1/2" per year and your new corner supports do not sink, your support design would have the entire structure supported by just the 4 corners in a short time. Normally the entire perimeter of the structure supports the structure. Doesn't sound like a good fix. I don't know of a cheap solution. We would normally add support piers underneath the perimeter at some distance apart set by soil conditions and load carried.

Note: I am a general mechanical engineer that has built houses before....but not a structural engineer. Maybe others know more and can provide better advice.

 

[CRLLS]

I can relate. I had a house w/attached garage sink in one corner. It dropped about 9 inches over about 35 ft length of foundation. Foundation was dug out to inspect. It was built to code. Architects, City building dept, contractors were consulted. Nobody could say why it was sinking. We had a $1,000 soil survey done. Soil borings to about 12 ft showed it was stable ground. Should be suitable to build. We drove pilings and transferred the weight of the foundation from the footings to the pilings. $25,000 later, it was fixed. I wish you luck.


If the foundation & walls of your garage are both sinking, but the floor is not, your solution may slow down the inevitable. But then what? It doesn't hurt to try. Be careful of tripping on that floor 4x4.

 

[travelover]

My first house had a saggy one car garage with a crappy foundation and the cement floor was collapsed concave in the center .

My late FIL was a building inspector and a practical guy and he suggested that we jack up the garage, tear out the floor and pour a new floor with re-rod that extended under the walls. This we did and it worked great, although it was a lot of work.

Edit: Just looked it up on Google street view and it looks fine 34 years later.

 

[eytonxav]

I'm not a building engineer... but I'm married to a former architect and have sat in on a lot of conversations involving stuff like this. (Although mostly with retaining walls or houses, rather than garages.)

It seems like part of the problem is lack of proper foundation. Until that is addressed, it seems like you'll continue to have problems. You might need to trench and pour at least some sections of new foundation...

That said - my degree was in engineering of the electrical type... not structural.

+1, have a foundation specialist look at it. Also, EE here.

 

[calmloki]

Yours is a much nicer and more substantial looking building than the ones I jacked up - I had rotten support studs going to rotten wood to earth lower beams. Horrible construction, but dryer beneath than out in the rain, so..

Building one, jacked the board and batten walls up out of the dirt, supported the building with some posts on concrete pads, dug a sloped from the inside out to the square dirt left by the walls coming up edge, had a concrete truck chute through a window fill the monolithic floor/footing, leveled concrete, replaced the rotted studs, ran PT around the walls to sit the studs on (had some blank areas where the support pads were), re-lifted the building and set it back down on the new pad.

Building two I just put PT 4x6 on the gravel, jacked the building up by the upper plates letting the walls hang from them, set level off the upper plates and cut needed new supports to the required length.

From your picture it looks like most of the sag is at the mid support by the man door - could you get your 15 years by redoing a pad there?

 

[Bamaman]

I'm just a lowly business school grad, but I essentially build constantly--on my 4 houses and for charity.

I'd jack that sucker up and dig 4 footings (to code) under each side wall and one in the middle of the back wall. I'd tie into the existing wooden structure and fill each footing with concrete. It won't go anywhere. I do much of such jobs with my gas powered post hole digger.

I have a cousin and three close friends that are architects. I always avoid them on building issues, as architects (even when free) always cost me money doing things the "hard way."

 

[Ronstar]

I'm not a structural engineer, but surveyed many buildings, refinery tanks, etc to measure settling. If it's settling at 1/2" per year - that's a lot. I'm not sure that your simple fix will stop the settling. The only way I know of to stop the settling is install pilings or footings down to stable soil.


Sent from my iPad using Early Retirement Forum

 

[ls99]

Lessee, 1/2" per year, 10" in 20 years +/-. Cheapest solution is trim the door(s) and have small sports cars.

Chances are the settling will slow as the soil gets compacted by the weight, so possible the sinking will diminish over time to say 1/4" per year. In thirty years you probably won't care.

 

[meierlde]

Lessee, 1/2" per year, 10" in 20 years +/-. Cheapest solution is trim the door(s) and have small sports cars.

Chances are the settling will slow as the soil gets compacted by the weight, so possible the sinking will diminish over time to say 1/4" per year. In thirty years you probably won't care.

The post says that the garage is 100 years old, so in most cases settlement should have been complete. Just out of curiosity is the house settling as well or not. If not then the problem is not the ground but the way the foundation for the garage was built.
Note that the settling must have started recently as 1/2 inch per year for 100 years is over 4 feet. Has any mod to the garage been done recently in particular anything that added to its weight?
Is this in an area of sinkholes, which could explain a difference in settlement rates over parts of the lot? Any new big wells installed in the area?

 

[marko]

The post says that the garage is 100 years old, so in most cases settlement should have been complete. Just out of curiosity is the house settling as well or not. If not then the problem is not the ground but the way the foundation for the garage was built.
Note that the settling must have started recently as 1/2 inch per year for 100 years is over 4 feet. Has any mod to the garage been done recently in particular anything that added to its weight?
Is this in an area of sinkholes, which could explain a difference in settlement rates over parts of the lot? Any new big wells installed in the area?

OP here and thanks for the current replies.
No, the house is relatively solid and level. It does seem that the settling began about 30 years ago but there hasn't been any good reason; no sinkholes, added weight or anything.

We're one of those weird people who actually use our garage to put cars in so I do hope to keep the building up for a bit. I think I'll get a building engineer (have a friend who's the local building inspector) and get some ideas.

Nobody asked but the reason the third bay stopped being a parking bay and was turned into a blank space was that back in the 40's, my grandparents (who owned the house before me) owned monkeys and made that area the pen (yeah). They were big party people and the idea was to get the monkeys drunk for what was viewed in those days as 'entertainment'. I know, nowadays, they'd be arrested, but......

 

[travelover]

.................Nobody asked but the reason the third bay stopped being a parking bay and was turned into a blank space was that back in the 40's, my grandparents (who owned the house before me) owned monkeys and made that area the pen (yeah). They were big party people and the idea was to get the monkeys drunk for what was viewed in those days as 'entertainment'. I know, nowadays, they'd be arrested, but......

That would have been my second guess......

 

[marko]

OP here.

So, after some inputs I did a more detailed investigation.

Again, what the building's vertical studs are sitting on is a mystery as they've sunk down too low but I suspect it may have been no more than some timbers.

As noted, the inside of the garage was hot topped once or twice and that doesn't move...so the floor stays put but the studs slide down. The hot top goes right up against the inside wall and in between the studs.

My new thought is to cut some 4X4s about two feet long, place them on the stable floor and against the each of the sinking studs and lag-bolt them up. That way I'd have a two dozen or so points of support.

Yes, I know I'm not "doing it right" by refooting the whole mess; if it comes to that level of expense, I'll just tear the thing down and start over. As noted, I'm just trying to stop the sinking and have the thing stay up for the next 15 years or so.

Does this sound like a better approach?

 

[Sunset]

At 100 yrs old, a good chance the building was built on posts stuck in holes in the ground. Now that they are rotting, it's sinking.
I have a 2 story house with this issue built 96 yrs ago.

The floor does not sink as its not attached to the walls, it floats on the surface of gravel and has little weight per sq foot.

Personally I'd dig a hole on the outside to check/confirm the "foundation" is posts/wood, it will answer questions as to why it is sinking. Because if you dig and find concrete footings, then perhap the soil has changed or a small sinkhole is developing as these are common in FL

If it is wood.
You could jack up and support the walls, cut the walls off where not rotted, dig down post holes for concrete pillars, and span between the pillars with PT beams.
Then set the walls down on the beams.


I'm not an engineer, but put a bunch of concrete pillars under my old home.

 

[Sunset]

OP here.

So, after some inputs I did a more detailed investigation.

Again, what the building's vertical studs are sitting on is a mystery as they've sunk down too low but I suspect it may have been no more than some timbers.

As noted, the inside of the garage was hot topped once or twice and that doesn't move...so the floor stays put but the studs slide down. The hot top goes right up against the inside wall and in between the studs.

My new thought is to cut some 4X4s about two feet long, place them on the stable floor and against the each of the sinking studs and lag-bolt them up. That way I'd have a two dozen or so points of support.

Yes, I know I'm not "doing it right" by refooting the whole mess; if it comes to that level of expense, I'll just tear the thing down and start over. As noted, I'm just trying to stop the sinking and have the thing stay up for the next 15 years or so.

Does this sound like a better approach?

By hot topped I think you are saying pavement, if so, your plan won't work as pavement gets soft in hot weather and the posts will sink into the pavement over time. It might sink slower than it is sinking now.
To improve on your partial solution:
If you made feet for your scabbed 4x4's to spread the weight they will sink slower ( using PT you could make a U shape 2x4 to fit tightly between each wall stud , no need to use 4x4)

 

[pb4uski]

What you probably need to do is to jack it up to where it was (or perhaps a little higher). excavate under the walls, put in a proper footing/foundation, and then lower the structure onto the new footing. That assumes that the sill plates are not rotted... but they probably are so you'll likely need to replace the sills and sister in some 2x4 studs.

If you want cheap then perhaps you could put a PT 2x6 on the ground along each wall, and nail a 2x6 along the ceiling joists along the wall and then buy some suitably sized jack posts and put them in. My thinking it that the load will be distributed over a larger surface and the settling may decline... but that is a bit of a jury-rigged solution.

Or tear the sucker down, pour a perimeter reinforced floating slab with some foam board to prevent frost intrusion and rebuild.

YMMV and I'm an accountant, not an engineer so what do I know.

 

[meierlde]

One question is the location one where the ground freezes which can make settlement worse? Typically you are supposed to dig footings to below the freeze line so the building does not move with the seasons. (Around Detroit that is 48 inches deep for example)
But replacing the foundation typically is best done by a foundation company, and depending on where you live may well require a building permit with an engineers report as well. Foundation companies do this a lot with peer and beam homes when the central peers sink, dig out and put in concrete peers.
But at 100 years old you should evaluate replace versus repair as options)

 

[marko]

and depending on where you live may well require a building permit with an engineers report as well.

Off topic, but, where I live you need a permit to scrape paint. Literally; you cannot scrape loose paint without first going to town hall for a permit.

On some of our historic streets you cannot plant certain flowers unless they were available locally in the 1800's nor paint the house colors that weren't around in those days.

Jacking up a garage would take close to 3 years of hemming and hawing by the building inspector and it may/may not be approved...

Anything that can be seen from the street would need approvals so, lots of ummm 'projects' are attempted inside the walls.

 

[Ronstar]

If you want it good for 15 years or more, I'd tear it down and start over.

 

[pb4uski]

....Typically you are supposed to dig footings to below the freeze line so the building does not move with the seasons. (Around Detroit that is 48 inches deep for example)...

You don't necessarily have to go so deep as long as you put foamboard around the perimeter of the foundation and outwards before backfilling to prevent the frost from getting to the foundation. That approach was pioneered in Scandinavia and my contractor used that approach on the foundation of our lake home since the water table was too high to put in conventional footings and frost walls and it has worked like a charm... never had a crack in the 4 years since we did the foundation. I was skeptical at first but did my research and found out it works. Ditto for the garage perimeter reinforced slab.

http://www.finehomebuilding.com/des...ails/frost-protected-shallow-foundations.aspx

 

[ERD50]

At 100 yrs old, a good chance the building was built on posts stuck in holes in the ground. Now that they are rotting, it's sinking. ...

Agreed, that seems more likely than sudden unexplained settling after 100 years.

...

Jacking up a garage would take close to 3 years of hemming and hawing by the building inspector and it may/may not be approved...

Anything that can be seen from the street would need approvals so, lots of ummm 'projects' are attempted inside the walls.

If you want to do it from the inside, I'd still look at temporarily jacking up the walls (maybe screw a 2x6 along the two walls in the sinking corner, and use a bunch of those post jacks to lift it up a bit, with the jacks on another 2x6 on the pavement to spread the forces). There might be enough space to just pour in cement in the empty space underneath, or break out a few inches of the pavement where needed.

Since you aren't looking for a long term fix, I wouldn't worry about frost heave. It looks like it's survived 100 years w/o a frost-line foundation, what's another 15 years?

If the sill plate is completly rotted in places, you might need to jack it up enough to slip a new PT sill in there. But I think you could do that w/o anyone noticing from the street?

edit/add: Depending how much work this will be, is it worth it for 15 years? Why not put in new now?

-ERD50

 

[Htown Harry]

Long post. Skip to the end for my advice.

Civil engineer here, but I don't deal with structures or foundations much. I'll give some very general comments on the basic principles I learned in college.

The design of a building structure and its foundation are completed sequentially, then fine-tuned to work together.

Step One in structural design is to add up the loads on a structure, in this case the garage. These are called design loads. Absent earthquake loads or other extraordinary factors, there are two types of design loads.

Dead loads are the forces exerted as a result of gravity and the mass of the building components acting on each other. The weight cascades from the floors and the roof downward through the walls to the foundation.

In this case, the total dead load of the weight of the building is distributed primarily around the perimeter walls.

The dead load is not transferred uniformly to various locations on the foundation. The magnitude of the load will vary based on the characteristics of structure above. For the back wall and side walls, the dead load on the foundation might be calculated as a relatively uniform X lbs. per linear foot. Where door openings are present, the weight of the structure above a door is transferred via the door header beams to the adjacent walls on either side of the door. So if the total weight transferred to the foundation from the walls is the same on the front as in the back of the garage, then the walls in the front will be transferring X+ lbs. per linear foot to the foundation. In the same load is transferred to a shorter sill plate distance due to the door openings, creating a greater force per linear foot.

Live loads are the second type. They vary from day to day. They include snow, wind, the contents of the building, etc. Building codes will prescribe how a structural engineer should calculate the live loads and various safety factors, but the overall effect is that the calculated building load transferred to the foundation will be bumped up to X++ lbs. per linear foot.

The design load calculations above generally assume the foundation is the Rock of Gibraltar, fixed and immovable.

The foundation design comes next. Since building the Rock of Gibraltar is impractical, the designer's task is to come up with a design that is good enough to support the design loads in an economical, code-complaint fashion.

Whatever the foundation type, the building loads are transferred through the foundation to the earth. So question #1 for the foundation designer is "how strong and stable is the earth at this site?"

I'll skip the details of soil types, but the investigation of the soils will result in a determination of the load-bearing capacity of the different soil layers. Stability can be affected by slopes, soil type (especially expansive clays), ground water characteristics, moisture variations, frost depth and some other factors.

The soil can be modified to alter the factors, but usually is not for a residence. As with the structure above, codes affect how the various strength factors are calculated. The end result is a calculation that says a foundation bearing at Y ft. depth can more or less imitate the the Rock of Gibtaltar at up to Z lbs. per square foot of downward pressure.

The next to last step is to select foundation materials and cross-sections that transfer the wall loads through the foundation to the soil.

The last step is coordinating the connections between the house and the foundation so that the house doesn't slide, lift up or topple when wind exerts a sideways shearing force parallel to the ground.

(I've just summarized about 12 semester hours into a few paragraphs. There's more to each step in a real design.)

I say all of that to give the OP the background on the order to troubleshoot the source of the problem.

First, eliminate changes to the structure's dead load as a cause. Too many layers of shingles? Several grand pianos stored in the attic? Doors added, creating greater wall loads per linear foot?

Next, think about whether there have been changes to the soil conditions around and under the foundation. The likely suspects all fall into the category of water being bad for soil strength and stability. Did the gutters and downspouts get removed? Did the water table rise? Did grading around the foundation hinder water's ability to get away from the foundation?

If changes to the loads from above and changes the soil's bearing capacity below can be eliminated as root causes, then you pretty much know that you either have an inferior foundation design or deterioration in the foundation materials is the root problem. Given the age of the house, deterioration is the leading suspect.

I'm with Sunset. Hire a neighborhood kid or a day laborer and start digging around to see parts of the foundation. You should know what has failed and why before making decisions on whether to replace or repair the original design.