strip width of underpinning a crawl space and transferring it to a basement: Rubble stone foundation 3

[geebader]

Hello,

1-Could anyone help me please identify the strip width normally used for underpinning a two story house?
2-In addition to that I need to add a door to the crawl space since the only entrance is from inside.

3-Is there any recommendation or links how to proceed making that door without risking any settlement of the foundations?
4-Do we need to add Keyways between the strips?
5-What is the best way to seal the joints between those strips?

Thank you very much for your help?

 

[dicksewerrat]

First call the local building inspector.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[geebader]

why do I need to do that?

 

[dicksewerrat]

You are changing the house, adding basement area, doorways, etc. and you don't know how to add a door without wrecking the existing foundation.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[geebader]

I thought this forum is for sharing experiences and knowledge, thanks anyway for your time.

 

[dicksewerrat]

You start at the building inspector and he/she will guide you through to which people can do this work and who should do the design if required. You have "rubble stone' for foundation. there is as much art as science to touch that.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[geebader]

I have inspected the house, and I was wondering concerning adding a door I have seen people building a beam on two concrete columns around that opening to transfer the load around the opening? Is it really necessary to be done this way? And I ve seen them doing a temporary beam then another permanent beam underneath it to be on the safe side.

If anyone can clarify please if there is a faster way because this procedure requires everytime the concrete to get cured before digging again the full opening.?

Thanks

 

[jayrod12]

With rubblestone foundation that is pretty much the only way to go.

One time we removed the rubblestone from the doorway area right up to the underside of the floor joists (approximately 42"x84") and then provided a steel frame around to support the floor and stiffen up the walls laterally. The owner needed a custom cut door to fit the opening as by the time it was done the door rough opening was just less than 6'-6".

 

[geebader]

Thank you Jayrod12. Do you know based on what we should determine the width of the concrete strips, underneath the rubble stone? I know that the practice is 4' width. But can we always apply it?

 

[jayrod12]

I don't have a hard and fast rule. In the end it's up to the contractor. If you are getting someone reputable they will have their own ideas. If you are concerned about the integrity of the wall then you could do it in 3 foot strips. Likewise if you are confident you could look at doing 5 foot strips.

It's also a function of wall height.

Call a few of the underpinning contractors in the area and see what they recommend.

 

[RHTPE]

1 - Strip width will likely be influenced by the size of the stones used in the foundation. Where is the project located?
2 - Adding a door is possible but this question is tough to address without knowing the nature of the framing that bears on the foundation.
3 - Underpinning is never without some risk of settlement.
4 - Horizontal keyways would be advisable.
5 - Hydrophilic waterstop (Volclay RX or similar) is probably the easiest, although with a rubble foundation you may still experience some ground water infiltration. Since it sounds like you will be exposing the entire foundation an exterior ground water control method may be in order (stone + perforated pipe to daylight).

Ralph
Structures Consulting
Northeast USA

 

[PEinc]

The WIDTH (along the wall) of the underpinning piers will depend on the condition of the rubble stone wall. Usually, this width is 3 to 4 feet. If the wall is in bad condition, it may need to be re-pointed, shotcreted, or the underpinning width may need to be reduced. I also have underpinned buildings where we had to remove the rubble stone wall in sections and pour the underpinning concrete up to within about 2 or 3 inches of the brick wall which was then dry packed.

http://www.PeirceEngineering.com

 

[geebader]

Thank you for all your answers.
The property is in montreal, i was thinking to do like french drain with a sump pit somewhere to take all the water. The house has brick siding.

I assume there is a need to have some reinforcements for shrinkage that do not need to have a development length, otherwise it will be difficult to for the contractor to do.

The only concern is that the underpinned foundations will be working with no integrity due to the fact of having a joint every 4 ft.
Based on your experience is there any problem with that. The crawl space needs to be extended by 4 ft.

Thanks

 

[PEinc]

Normally, underpinning has no reinforcing steel. Plain, unreinforced concrete is stronger than rubble stone walls which were used commonly for residences with basements.
If you are underpinning in order to deepen a crawlspace into a basement, your bigger problem will be providing lateral support for the underpinning and the original rubble stone which will remain above the underpinning.

http://www.PeirceEngineering.com

 

[geebader]

Pinc, could you suggest an economical way to provide lateral support? between the rubble stone and concrete dry pack will provide the bearing transfer, but laterally the own gravity weight seems not to be enough.

 

[PEinc]

The weight of a relatively small, residential building usually isn't enough and the lateral analysis (overturning and sliding) is too often mistakenly ignored. Unless the underpinning is only a few feet deep or the building is very heavy or the piers extend well into the basement area, lateral stability will be a problem. The easiest solution is to let the front of the piers extend into the basement about a foot or two. This increases the moment arm for the dead load force that resists the overturning. Unfortunately, no one wants to reduce the width of their basement to accommodate the bigger piers. Your other option is to underpin from outside the wall (unless this is a row house) and let the piers extend outside the building to give you heavier piers with more moment arm to resist the overturning. However, this is not as efficient as having the piers extend into the basement. You also need to check sliding which is often another problem with light buildings.
You really can't brace the underpinning. If you could extend the underpinning up in front of the rubble stone wall, you cold possible use the floor joists to brace the underpinning but that would require reinforcing steel and the underpinning would still have to extend into the basement in order to brace the front of the rubble stone wall.
Last, but probably least desirable, you could tie back the underpinning piers with tieback anchors (e.g. helicals, manta rays, grouted anchors, etc.).

http://www.PeirceEngineering.com

 

[geebader]

Thank you very much for sharing your experience! Your comments are so valuable

 

[oldestguy]

Have you involved a getechnical engineer to advise on soil bearing pressures allowable as well as the likelihood of being involved with expansive clay there? My memory tells me that area has plenty shrink-swell problems that may have to be addressed.