Structural Engineer - Help

[Newview01]

Wood Foundation - (6'9" ceiling height, 2x8 treated walls), can I add a 2' pony wall to increase basement ceiling height without too much stress to the current walls? The only additional weight would be the weight of the pony wall. Realistically, that weight is probably offset by the ultralight drywall in use these days. Just thought I would double check.

[owlhoot]

I'm not an engineer.
If you are adding a pony wall on top of existing I see the joint as a weak spot

[Jeron Kahyar]

Is this a load bearing wall your are replacing? If not then you are likely fine. If it is; this is not something to just "wing it" on. Get a proper assessment for load bearing wall modifications.

[dewalt18]

Structurally, I don’t see any reason you couldn’t do it, so long as you have engineered drawing and obtain all required permits. That being said, if there’s already a house built above the basement, you’ve got a lot of work to do to gain two feet. Stairs would need to be altered or replaced, likely not going to be 2’ of slacknin your electrical lines, plumbing and havoc would have to be altered as well. As well as the work required to raise the house to get the new walls in. . .

[Arty]

Whether an engineer or not, the best way to answer the question would be to take a look at the forces typically acting on the structure, and determine if the changes would exceed the intentions of code spec, or of previous explicit analysis & design.

It seems the main static forces resisted by a basement wall (assuming no earthquakes or dynamic internal loads) are: a) vertical gravity loads of the building on the basement, b) uneven loading of vertical forces along the wall, and c) exterior 'caving' pressure on the side of the wall directed inward.

The vertical (a.) loads as resisted by the present wall would probably only change slightly due to the increase in weight of the additional wall. Probably not significant.

Uneven (b.) forces along a wall might come about by footing support becoming compromised over time, such as by a washout at one corner. So the top part of a wall might experience significant tension. If the new wall extension is not cantilevered, the addition might even make the whole wall slightly stronger against those forces, not weaker. So, not a concern.

The caving (c.) aspects are the most serious consideration. Wet dirt perpendicular against a typical residential basement can reach loads of well over one ton per linear foot. The higher and wider the wall which has to resist all of that, the more 'leverage' and total force presses against the diaphragm of the wall, pushing inward.

That's why ABC specifies a maximum basement wall height, and why all those deep high-rise building excavations you can watch during construction all have shoring which is reinforced with hundreds of perpendicular rods anchored deep into the surrounding soil.

So the main concerns are whether your wall extension ends up being below grade, the strength of the fasteners between upper and lower walls to resist both shear and tension, whether the new overall wall can stand the extra 'leverage' of the additional basement height, and what effect the extension actually has on the above-grade walls against wind loading and stacking forces.

I'd guess that if the total new basement height below grade is still within ABC limits, it might be OK as long as the original wall was within spec, the new wall is at least as strong as the old one per unit dimension, and if the new wall can be fastened strongly enough to the old one. And if the extension doesn't start to compromise the upper structure of the building.

Code or not, I'd do a thorough site survey of all aspects, conditions, and measurements, then use an acceptable model to run calculations and see if the structure can take those changes before making a decision one way or the other. Then get a second opinion by an actual foundations engineer. But that's just my approach.

[Norwest Alta]

The farmer in me says giv'er and I can't see why it would pose a problem but I suppose taking a core sample in to get it tested might be a reasonable thing to do. Better to be safe than sorry because the mix might not have the proper mpa. If I remember correctly from my concrete days is that there is different mpa rated concrete for different applications. I could also be wrong because I hated that job.

[LSLAKER]

If you wish to sell the building down the road you may find it nearly impossible to do so unless the purchaser has cash. Any lending institute would have the building inspected first and especially the wooden basement part. With no approved engineering for the basement construction and further changes it would become very difficult for one to borrow the money for the purchase.

[Arty]

Originally Posted by Jeron Kahyar

Is this a load bearing wall your are replacing? If not then you are likely fine. If it is; this is not something to just "wing it" on. Get a proper assessment for load bearing wall modifications.

What are you talking about? Do you have a clue?

Nobody's 'replacing' anything. And I highly doubt a wall of treated 2x8s would not be load-bearing.

[Jeron Kahyar]

Originally Posted by Arty

What are you talking about? Do you have a clue?

Nobody's 'replacing' anything. And I highly doubt a wall of treated 2x8s would not be load-bearing.

Easy now champ, no need to get your knikers all wadded here. Not sure what you are mad about other than appently an inadequate wording choice.

I don't know exactly what wall he is modifing or what it may be holding. So the advice stands; if you don't know get a professionals opinion. If you happen to have the engineered drawings, and know what modifications are being done, by all means sign off on the modified plans.

[Newview01]

Exterior walls, wood foundation, yes they are load bearing, as they hold up the entire house. No concrete involved (obviously footings, but not touching those). House has been completely gutted, no wiring/plumbing/ducting to worry about. Basement is only buried 4’ at most, so we would have more than half of the wall above grade.

We just bought the house, did not pay cash, and did not need an inspection. FWIW we had a magician of a mortgage broker.

So going off of previous comments, realistically is my only option is to put new studs all the way around to maintain “anti-caving” strength? Or is there a reliable, proper way to fasten the pony wall onto the existing top plate?

[Norwest Alta]

Sorry didn't realize it wood foundation. I only ever built pony walls on concrete but I can't see what the difference might be. Jack'er up. Build your wall and spike it down.

[Wrongside]

Originally Posted by Newview01

Exterior walls, wood foundation, yes they are load bearing, as they hold up the entire house. No concrete involved (obviously footings, but not touching those). House has been completely gutted, no wiring/plumbing/ducting to worry about. Basement is only buried 4’ at most, so we would have more than half of the wall above grade.

We just bought the house, did not pay cash, and did not need an inspection. FWIW we had a magician of a mortgage broker.

So going off of previous comments, realistically is my only option is to put new studs all the way around to maintain “anti-caving” strength? Or is there a reliable, proper way to fasten the pony wall onto the existing top plate?

You would need full height studs, preferably with a engineers letter. Otherwise, you would be creating a hinge point and severely weakening the foundation walls. With very few exceptions, hinge points/non-continuous studs/etc. are frowned upon in the building industry and by inspectors. The pressure from backfill can be enormous. Based on my years and experience building custom homes, I can't imagine any scenario where adding a 'pony wall' to the top of a wood foundation would be advisable.

I would highly recommend seeking the opinion of a professional engineer.

[Wrongside]

Originally Posted by Norwest Alta

Sorry didn't realize it wood foundation. I only ever built pony walls on concrete but I can't see what the difference might be. Jack'er up. Build your wall and spike it down.

There is an enormous difference between building pony walls on top of a properly engineered concrete foundation, and on top of any PWF foundation.

[Norwest Alta]

Originally Posted by Wrongside

There is an enormous difference between building pony walls on top of a properly engineered concrete foundation, and on top of any PWF foundation.

Thanks. Didn't realize this.

[expedition]

No way. Direct code violation.

[expedition]

Originally Posted by Norwest Alta

Sorry didn't realize it wood foundation. I only ever built pony walls on concrete but I can't see what the difference might be. Jack'er up. Build your wall and spike it down.

omg nooooooooooo

[Sneeze]

Originally Posted by expedition

No way. Direct code violation.

And exactly what part of the code would that be?

I honestly don't know the answer but I think it's fine. Talk to your municipal authority building inspections department.

Bet they ask for plans and a wall detail and stamp it almost as fast as you can pay em.

Jacking the house 2' will be a different matter!

[dmcbride]

Originally Posted by Wrongside

You would need full height studs, preferably with a engineers letter. Otherwise, you would be creating a hinge point and severely weakening the foundation walls. With very few exceptions, hinge points/non-continuous studs/etc. are frowned upon in the building industry and by inspectors. The pressure from backfill can be enormous. Based on my years and experience building custom homes, I can't imagine any scenario where adding a 'pony wall' to the top of a wood foundation would be advisable.

I would highly recommend seeking the opinion of a professional engineer.

I am no engineer, but this would be my worry.

[expedition]

Originally Posted by Sneeze

And exactly what part of the code would that be?

I honestly don't know the answer but I think it's fine. Talk to your municipal authority building inspections department.

Bet they ask for plans and a wall detail and stamp it almost as fast as you can pay em.

Jacking the house 2' will be a different matter!

code book all studs shall be continues between top and bottom plate. No intermediate plates allowed . On pwf foundations large knotts are not even allowed let alone a hinge point. Epic fail for sure.

[wildwoods]

We've framed a lot of buildings. That hinge point created and pressure from backfill would be an issue. Sistering 2x8's run thru the top plates continuously might be the answer. If you are in Edm try BIE engineering or Bogdan at IB engineering. They can help you. Personally I wouldn't want a hinged wall for a foundation wall, nor do I forsee anyone approving that. There might be some kind of simpson strong ties or strapping of somekind that will get you there, though. My $.02

[Newview01]

Thanks for the help.

If we go ahead with raising the house we will be replacing studs.

[spoiledsaskhunter]

Originally Posted by Newview01

Thanks for the help.

If we go ahead with raising the house we will be replacing studs.

...trying to picture this. as in removing the top plate and adding longer studs? sometimes it's better to start over rather than try to jury rig something (at least in my years of trial and error, it always seems i should have done it the hard way the first time and had it right)

sounds like quite a project. hope you will let us all know how it turns out.

[densa44]

I would not recommend a home made solution, regardless of how good it is. The next customer for this house will not have the same mortgage broker that you had and he will want to see a piece of paper saying that the basement is built to code, what ever that is.

You could be destroying the value of your house.

Be very careful here.

[alpineguy]

Originally Posted by Wrongside

You would need full height studs, preferably with a engineers letter. Otherwise, you would be creating a hinge point and severely weakening the foundation walls. With very few exceptions, hinge points/non-continuous studs/etc. are frowned upon in the building industry and by inspectors. The pressure from backfill can be enormous. Based on my years and experience building custom homes, I can't imagine any scenario where adding a 'pony wall' to the top of a wood foundation would be advisable.

I would highly recommend seeking the opinion of a professional engineer.

Originally Posted by Wrongside

There is an enormous difference between building pony walls on top of a properly engineered concrete foundation, and on top of any PWF foundation.

This is correct^^^
Having built a few wood basements myself there are a couple crucial points to the wall construction and anchoring.

-Firstly, you absolutely need an Engineer stamped drawing to perform any changes to your PWF foundation
-The floor is a key component to the basement as it is anchored to the walls to keep them from buckling under the sheer stress caused from backfill
-If you put a pony wall on top of an existing wood basement a hinge point (as noted above) creates a weak point in the new wall structure
-An engineer may be able to overcome the hinge point issue by having sheer walls installed to compensate

[Wrongside]

Originally Posted by alpineguy

-Firstly, you absolutely need an Engineer stamped drawing to perform any changes to your PWF foundation
-The floor is a key component to the basement as it is anchored to the walls to keep them from buckling under the sheer stress caused from backfill
-If you put a pony wall on top of an existing wood basement a hinge point (as noted above) creates a weak point in the new wall structure
-An engineer may be able to overcome the hinge point issue by having sheer walls installed to compensate

All excellent points.

[Albertadiver]

Originally Posted by alpineguy

This is correct^^^
Having built a few wood basements myself there are a couple crucial points to the wall construction and anchoring.

-Firstly, you absolutely need an Engineer stamped drawing to perform any changes to your PWF foundation
-The floor is a key component to the basement as it is anchored to the walls to keep them from buckling under the sheer stress caused from backfill
-If you put a pony wall on top of an existing wood basement a hinge point (as noted above) creates a weak point in the new wall structure
-An engineer may be able to overcome the hinge point issue by having sheer walls installed to compensate

I'm in the industry, and while I don't have a P.eng I did stay in a Holiday Inn once. This is good advice above. If you need contact info for a few structural engineers I'm happy to connect you to a few reasonable guys that I trust.

[Newview01]

Before I go the engineer route, what if I were to "crutch" two studs together? I.E. if I am adding 2' of stud on top of the existing stud (after removing top plates) with a 5' brace/crutch glued and screwed to both. I guess maybe it's adding a point of failure but the weight and bracing should theoretically prevent any type of caving failure.

Or am I wrong.

P.S. yes I am too cheap / not enough in the budget to go the engineer route, unless he rubber stamps my "design".

[Wrongside]

I tell the guys on my crew, "Do it right, or don't do it at all."

[expedition]

Originally Posted by Newview01

Before I go the engineer route, what if I were to "crutch" two studs together? I.E. if I am adding 2' of stud on top of the existing stud (after removing top plates) with a 5' brace/crutch glued and screwed to both. I guess maybe it's adding a point of failure but the weight and bracing should theoretically prevent any type of caving failure.

Or am I wrong.

P.S. yes I am too cheap / not enough in the budget to go the engineer route, unless he rubber stamps my "design".

do the engineer . Best money you will spend.

[Norwest Alta]

Originally Posted by expedition

do the engineer . Best money you will spend.

Sure a engineer is fine but they are not always right and do make mistakes that they are not held accountable for. Personally I'd talk to alpine, wildwoods and or wrongside. All three seem highly knowledgeable.