Custom home renovation with no drawings 1

[Said the Sky]

Hello,

I have a 30 year old custom home renovation, was cast with concrete foundation, likely typical 8" wide concrete walls on strip footing, however I don't know the size of the footings and no drawings available, nor bearing pressures, however we can get some tests done to verify this.

The house was a two story home with a entire floor added where the roof use to be, and a new roof build above that. There are quite a bit of beams added with substantial vertical point loads coming down on foundation exterior concrete walls. There was even an elevator added in.

how would you go about finding the information required to do any checks? I believe if it is 8" wide walls it will be acceptable, it takes quite a bit of load to overwhelm 8" wide concrete walls, however the strip footing I am a bit concerned about the point loads coming down. I would of course check it assuming the load distributes in a 2 vertical to 1 horizontal uniform load on the strip footing and any overlap of point loads adjacent to each other.

 

[Harbringer]

Is there signs of settlement? Are you adding a third floor? The answer depends on what question you are trying to answer.

 

[Said the Sky]

adding a third floor - it is actually already installed, they now want an engineer to come on site look at whats installed and determine if all the built up posts (stud packs) supporting the beams added are sufficient. I can figure that out no problem but I just dont know whats in the foundation, what the size of strip footings are. I can try to assume but thats not "duty of care".

I don't see signs of settlement, cracks in dry wall etc. but alot of the dry wall is opened up to add in the structure. Everything looks reasonable, it was designed by a standard structural supplier engineer, they just now want an engineer to say the base building can take those loads.

tia

 

[Harbringer]

If you know the age of the home then look to the residential building code of that time period and find the minimum prescriptive continuous footing.

You'd use code minimum bearing pressure unless you get a geotech involved.

 

[Said the Sky]

thats a good idea - thx

 

[phamENG]

If you need to check the footing, make them dig it up. Not the whole thing, but enough to feel comfortable.

That sounds like a mess. I'd avoid it if at all possible.

 

[Said the Sky]

yea thats what im thinking, if I cannot make the loads work even with minimum code requirements at the time - I think I will walk away

 

[phamENG]

Go that way anyway. I never certify a footing without measuring. I've found walls that missed the footings. Footings not built to minimum code, all sorts of stuff.

 

[HouseBoy]

I would not necessarily be "afraid" of this condition.
I suppose it is possible that footings were not used but I have never seen that (35 years concentrating on single family homes/probably average 150 to 200 projects in a year).
If you know who the builder was, their reputation might be a good indicator of what to expect.
Regarding bearing soil capacity (in US) residential building codes indicate allowable bearing for specific soil types. Most counties have an agency that provides soil maps.
An 8" concrete basement wall will go a long way to "spreading out" the loads.

I don't know if it's a good idea or not but it doesn't sound unreasonable that an "average" build should be capable of supporting 3 floors. As an example, we see two story homes with walk out basements (therefore 3 floors above grade) supported by "ordinary" footings.

Most "calculated" load in single family residential is from live load requirements but that live load does not ever materialize. Still, you gotta think about it.

What is the approximate load on a given wall footing? That would be a start. I'd consider how much is dead load vs. live load too as a way to make a judgement.

Just my $.02

I SHOULD ADD - making the addition without drawings is the real "red flag" to me... I wonder how anybody knew what to do!

 

[kipfoot]

I find that lateral loads on a 3 story house are more of a challenge than foundations. The term 'custom house' implies big open spaces and ground floor walls that are mostly windows. They may have called you to ask about posts and footings, but now your fingerprints are on the entire structure.

 

[Said the Sky]

thanks folks - were in a low wind and low seismic area which is great. not too many big open spaces except for the main entrance area where the ceiling goes all the way to roof which is pretty standard I think.

They installed a small tube (fits one person at a time) elevator that goes from the basement (sitting on slab on grade) that goes up to the new third floor which is like a den and gatherin area.

I've attached a picture - not sure if that helps since we can only upload one picture at a time

 

[Aesur]

I agree with kipfoot here, I believe the saying is you touch it you own it. I personally would walk away from this project and liability, there are too many unknowns without great expense and the possibility of needing to re-build portions (and you will be the bad guy for not rubber stamping). I would expect that the lateral system should be reviewed for diaphragms, drags, shear walls, overturning, holdowns, etc. Do you have access to review this or would you be relying on the contractor to "tell you what he did?" I have learned not to trust much of anything a contractor tells you he did as they won't put it in writing, the liability is yours and without the ability to verify it, it's unethical.

 

[XR250]

I'm in agreement with HouseBoy. I do this all the time.
If it is basement, I typically do not worry about it as the wall will spread out the load a fair bit.
If it is a slab or crawlspace, dig up the footing to determine its size and get some tests done.

 

[HouseBoy]

LVL rafters.... must be a big roof!

 

[Rabbit12]

How did it get to this point with no drawings? Seems really dumb to add an additional story without any drawings and presumably engineering.

 

[HouseBoy]

Perhaps I misunderstand the "no drawings" aspect. Is it that you don't have drawings of the ORIGINAL construction? That would explain why you don't know what the footings are...
I hope that you do have drawings of the current construction.

 

[JoshPlumSE]

Thirty years isn't so long ago. I take it you've got to the city or county looking for their drawings and they tell you they don't have any. Correct?

Do they have information about construction permits? Who applied for them and such?

I ran into an issue with my house when I was buying it. Mine is a tract home built in 1972. I have a floor plan that was used by the developer when marketing selling homes here in 1972. But, that's the best that I've got.

Then my house was added onto in 1983 ish. I've got the permit information from the add on that proves the house was inspected and signed off on. It shows who the engineer for the addition. It turns out that it was one of my neighbors.

Long story short, I called him up and said that I was in the process of buying the house and asked him about the renovation that was done in 1983 (which has some definite settlement). He's worked on a lot of similar re-models in this area, and we talked about what he thought led to the settlement and when it occurred and such. Great conversation. Great neighbor..... Made my wife a lot more comfortable buying a house with a settlement issue.

 

[Said the Sky]

Hello folks, to clarify a few things:

1) no original drawings from the original builder. Reached out to the city if they have anything and haven't heard back yet.

2) the third floor and roof addition is engineered by a typical supplier engineer, where they make sure their beams, rafters, joists are sufficient for capacity, but they don't check what it sits on, that would be my job. Also they got rejected by the city to get a permit before an engineer signs off on it, but in actuality they already built it....

3) I spoke with another engineer at the company (a old head) and he suggested just having the contractor dig up the foundation to measure height, width, and thickness of walls and strip footings. From there we can also test for bearing capacities.

4) problem is there is one corner of the house where it picks up a significant portion of the LVL beam point loads and distributes it on the wall, I will analyze the strip footing at 30 degrees to the vertical for equivalent uniform loading for most areas, however for one area we have point loads coming down beside two windows, so its only just a sliver of concrete supporting the point load (piece of concrete between two windows sort of like a column except its not reinforced like a column except for many 15M verts).

5) Actually when I did my walk through and a good 5minutes in I noticed that the point load stud pack from above didn't land on a lvl beam below, it was sitting on sheathing. If the roof were to ever be loaded with snow, and have any kind of live load on the new floor added, the whole thing would have came down. I love contractors.

6) more I think about this the more I want to walk away, its not worth the $$. Especially since its a side job of mine. I'd rather keep my license and practice another day.

another picture attached.

 

[phamENG]

more I think about this the more I want to walk away, its not worth the $$. Especially since its a side job of mine. I'd rather keep my license and practice another day.

Good idea.

 

[HouseBoy]

The footing issues (your original question) do not seem insurmountable. There are several things that can be done to figure that out.
EVERYTHING ELSE.... I would walk... if I could.