Structural Engineering

Ask Structural Engineering Questions and Get Expert Answers ASAP

Ask an Expert,
Get an Answer ASAP!

This answer was rated:

I have an existing basement slab-on-grade, approx. 2-years…

I have an existing...

I have an existing basement slab-on-grade, approx. 2-years old. There are portions of slab that have settled, cracked and require replacement. The original building is going to remove these sections and re-pour. The correct method is in question. Slab is approx. 3.5" thick, non-reinforced, 6-mil vapor barrier. I would assume the builder will saw-cut small portions to be removed. Diamond Dowel and epoxy. I am considering an independent testing agency to determine the existing compaction rate as a "Baseline". Ultimately the builder and Eng or record shall determine the corrective action, I will be observing, and want to make sure work is proper. I looked throught IRC and ACI, and was not able to find specific means & methods.

Tutor's Assistant: OK. Is there anything else important you think the Structural Engineer should know?

Any details and/or guidelines is greatly appreciated. Thanks Joe Burke

Show More
Show Less
Ask Your Own Structural Engineering Question
Answered in 20 minutes by:
3/12/2018
walkereng
walkereng, Consultant
Category: Structural Engineering
Satisfied Customers: 3,004
Experience: Over 30 years of Structural Engineering experience.
Verified

Do you have any pictures you can share with me?

There is a button on the Chat Window that allow you to attach files.

Ask Your Own Structural Engineering Question
Customer reply replied 4 months ago
I would have to see if I have any photo's. The home builder, structural engineer, building department and so forth are engaged. Over this time period, it is concluded that structural deflection, shift, etc. is not the cause. I believe basement slab settlement is due to poor compaction / workmanship. two locations are around the sump-pump pit and at the base of the precast stair. Control joints have little with creep. Based on this, I just wan to see how the replacement concrete should tie at the slab to remain, should it be doweled, float, tie to perimeter foundation wall. Once the sections of the slab is removed, I might be able to see the sub-base soil material as well. If compaction is poor, should compaction grouting, or expansive foam injection be added? Don't think any aggressive compacting should be applied.
Thanks
StructuralEng
StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 7,716
Experience: Structural Engineer
Verified
Hello. I can help.
Ask Your Own Structural Engineering Question

If your contractor is going to sawcut the sections that have cracked, you will want to check the existing compaction under the removed areas, then you will want to recompact the areas in question with mechanical compaction methods (you do not need compaction grouting, etc.). You should provide dowels into the existing slab to tie the new into the existing. The best method for your dowels would be to dowel the rebar into the holes drilled into the existing slab with epoxy. Epoxy dowels are better than mechanical expansion anchors.

If you feel you have received a satisfactory answer to your question, please click the Rating button that is appropriate. Experts are credited for each adequately Rated answer they provide. If you have additional questions, please let me know. Thanks

Ask Your Own Structural Engineering Question
Customer reply replied 4 months ago
Hi
I didn't receive a recommendation.
thanks
I responded above at 22:51, do you see it?
walkereng
walkereng, Consultant
Category: Structural Engineering
Satisfied Customers: 3,004
Experience: Over 30 years of Structural Engineering experience.
Verified
walkereng and 87 other Structural Engineering Specialists are ready to help you
Ask your own question now
Customer reply replied 4 months ago
hi,
Sorry Have another question on same topic; as outlined below.
This message is not letting me attached a file; The construction documents details are vague and limited; the engineering drawings detail appears that the design intend is that the foundation wall (8") is seated on the footer. It seems the basement floor slab could possibly seat on top of the footer (Not a monolithic pour). Detail does not show a turndown rebar for interconnection of the basement slab to footing.
So, the my final questions are:
1) If the bottom-side of slab is seated at the top of the footer, and no turndown rebar installed, should dowels be installed to tie the slab to the footer? Or just float?
2) Should they be inserting dowels where the replacement basement slab-on-grade meets the existing foundation wall or float at this point?
3) Should heavy tar paper be placement between the replacement slab and existing foundation wall. Keep in mid that the vapor-barrier must be maintained.
4) Any suggestion of the dowel size for a 3.5" think slab? I assume dowel spacing should be 12" on center, with insertion depth a min. of 8", any thoughts?
5) How they installed the 6-mil vapor barrier will be interesting. I would expect to find the vapor barrier to be continuously up the perimeter foundation to the top edge of the slab, then the abutted edge epoxy sealed.Your help and input is much appreciated, It well exceeds my expeditions.
Thank you!

1. No, not necessary.

2. Floating is fine.

3. Yes, you can use the tar paper as a bond breaker.

4. 3/8" diameter rebar, 12" long +/-, with 6" doweled into the existing concrete areas and 6" into the new pour area. You can space these at 18" o.c.

5. That can work, I would leave that up to the contractor as to the most practical way to install.

I hope this helps.

Ask Your Own Structural Engineering Question
Customer reply replied 4 months ago
Just awesome!
Thanks

Good Luck with your project!

Ask Your Own Structural Engineering Question
Was this answer helpful?

How JustAnswer works

step-image
Describe your issueThe assistant will guide you
step-image
Chat 1:1 with a structural engineerLicensed Experts are available 24/7
step-image
100% satisfaction guaranteeGet all the answers you need
Ask walkereng Your Own Question
walkereng
walkereng
walkereng, Consultant
Category: Structural Engineering
Satisfied Customers: 3,004
3,004 Satisfied Customers
Experience: Over 30 years of Structural Engineering experience.

walkereng is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here.

DianeDallas, TX

< Previous | Next >

Meet the Experts:

walkereng

walkereng

Consultant

3,004 satisfied customers

Over 30 years of Structural Engineering experience.

vgdlpc

vgdlpc

Master's Degree

17 satisfied customers

Civil Engineer, Major in Structures and Foundations. Professional Engineer 11 years of experience.

StructuralEng

StructuralEng

Consultant

7,716 satisfied customers

Structural Engineer

Matt

Matt

Engineer

45 satisfied customers

Mechanical Engineering Hons degree, been working in automotive industry for the last 18 years - Engine development engineer

ibosley

ibosley

Master's Degree

88 satisfied customers

Mechanical Engineering

Ellen

Ellen

Consultant

109 satisfied customers

attorney and legal researcher

P. Simmons

P. Simmons

Attorney

149 satisfied customers

45 years old, retired Marine Officer, current attorney

< Previous | Next >

Related Structural Engineering Questions
We had a large new concrete driveway poured last Aug/Sep -
We had a large new concrete driveway poured last Aug/Sep - about 15,000ft2. I have two main concerns, firstly there is a fair bit of cracking which isn't on the cut lines. The contractor did drive a f… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
StructuralEng: I need info on an 8 foot high – 8” wide
For ExpertCustomer I need info on an 8 foot high – 8” wide poured in place concrete foundation wall (basement wall) for a modular (manufactured) one story home from the main floor to the roof. Footing… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
When a Hole IS excavated for a walkout basement, poured
HelloWhen a Hole IS excavated for a walkout basement, poured concrete walls, can the front of the house be shifted back a few feet if homeowner wants the house to sit further back off road? If so, doe… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
We have a home remodel with a room about 30' x 20' that has
We have a home remodel with a room about 30' x 20' that has new poured slab on grade. We noticed excess expansion of a control joints. We did borings that found poor to no compaction of fill under the… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
I'm replacing a first floor bearing wall. The opening will
I'm replacing a first floor bearing wall. The opening will be 13'10", carry a 28' span for a second floor and ceiling. The attic is accessible and could be used for light storage. Approx. 25' of 2x4 w… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
My cottage which is located only 30 feet from the lake has
My cottage which is located only 30 feet from the lake has a 6 foot crawl space (cement blocks) with a dirt floor. The moisture has started to rot the beams and mould has developed and the floor has s… read more
walkereng
walkereng
Consultant
Bachelor's Degree
3,004 satisfied customers
What is the proper technique to tie a new concrete slab foundation
What is the proper technique to tie a new concrete slab foundation to an existing one for a single story home?… read more
walkereng
walkereng
Consultant
Bachelor's Degree
3,004 satisfied customers
Is it possible to "foot" a floating slab building so that it
Is it possible to "foot" a floating slab building so that it can be attached to a new (not yet built) house? (Very northern Michigan) If so, what is the general process? Already Tried: emailed a local… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
I have a 40 foot wide, 9 foot high (with two 10 wing walls
I have a 40 foot wide, 9 foot high (with two 10' wing walls on each end) 'retaining' wall built that serves as one end of a pole barn. The contractor did not use enough enough re-bar and the wall has … read more
walkereng
walkereng
Consultant
Bachelor's Degree
3,004 satisfied customers
I am currently having a home built in South Eastern lower MI.
I am currently having a home built in South Eastern lower MI. The home is 85% closed in including roof, shingles, exterior/interior walls, and windows. The basement floor was poured late Oct 2013 afte… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
Hello, please what can I do to safely insulate below a concrete
Hello, please what can I do to safely insulate below a concrete slab that will be poured on grade? I have removed a slab from an atrium that was inside the perimeter of the existing foundation, and op… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
I live on the second floor of a 4 unit building (2 up, 2 down).
I live on the second floor of a 4 unit building (2 up, 2 down). Doing a kitchen remodel. Have to penetrate the slab for plumbing reasons. It's a 4" slab, set on 14" metal Hambro system (4' on center).… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
Dowels when adding a patio slab adjacent to existing slab?
When adding a 10'x15' 4" patio slab adjacent to an existing 6'x15' 4" patio slab, should smooth dowels be used in the existing slab to prevent a vertical offset between the two slabs? This additional … read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
I know dowelling is required when in-filling slab on grade
I know dowelling is required when in-filling slab on grade trenches (i.e. 24" x 8'0").....however, is dowelling required when pouring/infilling a +/- 3,500 SF slab-on-grade opening (poured back to exi… read more
walkereng
walkereng
Consultant
Bachelor's Degree
3,004 satisfied customers
My house is 3 years old and I am noticing some cracks in the
My house is 3 years old and I am noticing some cracks in the bricks in one corner of the house. The crack starts in the bottom corner an moves up and across. Right now it is not very big, but I am con… read more
walkereng
walkereng
Consultant
Bachelor's Degree
3,004 satisfied customers
Hi, I purchased a foreclosure house in the US. Once we
Hi, I purchased a foreclosure house in the US. Once we started renovations, my contractor discovered a hole under the tub. In further investigation, it was discovered that a previous owner had dug a r… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
Need to infill a 30"X30" opening in an existing 8" thick structural
Need to infill a 30"X30" opening in an existing 8" thick structural concrete slab. What needs to be done to the existing opening to prepare it prior to placeing new concrete? The reinforcing has alrea… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
I am building a 40 by 48 garage the foundation was recently
I am building a 40 by 48 garage the foundation was recently poured and there was a problem with a batch of concrete which forced the builder to remove the floor when this was done they cracked both fr… read more
StructuralEng
StructuralEng
Consultant
7,716 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x