Home Repair Building a Home Design Dilemma

Demo old home, keep existing slab as crawl space?

last year

We purchased an older home in SE Michigan that was a rennovated version of frankenstein's monster, a labrynth built on a slab on grade. Certain sections need regrading/improved drainage after 40 - 70 years of life in the clay, but the slab looks in really good shape.

We are downsizing and would like to build a house that is half the size. We want to explore using the existing slab as a crawl space and building around/over the top of it.

Plumbing is in the slab and seems to working fine, and the new plan has plumbing in similar locations to the old. HVAC, electrical, data and gas are currently routed through the ceiling.

Can we build new foundations in and around the slab? Our previous house had a cement crawl space under a new extension and it was super convenient. I like the idea of elevating the house a few feet above grade to improve water shedding.

Also could the freshly exposed sections of the slab be used for paving, parking spaces?

Sort by:Oldest

Comments (16)

PRO
HALLETT & Co.
last year
No the plumbing in the slab can’t be used at 70 years old, it’s a leak waiting to happen. Scrape and start over.
PRO
JAN MOYER
last year
last modified: last year
Get the bulldozer. Please : )

Show the new plan as something we can blow up and read
Related Professionals
Hillcrest Heights Handyman · Cloverly Kitchen & Bathroom Remodelers · Centerville Kitchen & Bathroom Remodelers · Asheville Painters · North Fort Myers Painters · SeaTac Painters · Charleston Architects & Building Designers · Dardenne Prairie Home Builders · Delano Home Builders · Everett General Contractors · Kettering General Contractors · Palm River-Clair Mel General Contractors · Fresno Kitchen & Bathroom Designers · Fort Wayne Furniture & Accessories · Woodstock Furniture & Accessories
PRO
GN Builders L.L.C
last year
x4
PRO
JAN MOYER
last year
Also, take the old "footprint" out of your head, start over. Unless convinced you need a house split to two halves and an entry courtyard . Get the architect back to the site, re - imagine without the constraints of the original.
Seabornman
last year
You wouldn't be saving much. Every edge of the existing foundation probably has a foundation wall that would need to be removed outside of the new footprint and where new foundation wall goes. That would include several feet on the inside of the new exterior walls in order to install new foundation walls, footings and footing drains. Add in the need for new interior footings, and you'll have a checkerboard of new slab/old slab. Also, a decent crawlspace height will substantially raise finish floor.

You may be able to leave the old footings.
lmckuin
last year
I have no help on the slab question, but except for being able to see the powder room toilet from the living room, I really like your floor plan.
latifolia
last year
The only time it's worth saving the old foundation is if zoning considers it grandfathered and will let you rebuild there which you otherwise wouldn't be allowed to do.
nickel_kg
last year
That was a huge house. I assume you've considered selling it and building elsewhere? Or, simply closing off some of the un-used space?
ci_lantro
last year
You want to repurpose 40-70 year old plumbing that is sunk through a slab?

Almost 100% guaranteed that the plumbing doesn't meet code. No plumber in his right mind would take that on.

Given the floor plan, this looks like a no expense spared build. Plumbing is strung from hell to breakfast for starters. So why even think about trying to reuse antiquated infrastructure?
PRO
Norwood Architects
last year
If you have a general contractor in mind I would consult with them about about reusing the existing slab. As someone else pointed out the plumbing is probably at or beyond its lifespan. You will invariable have to do some trenching in the slab even if new plumbing fixtures are relatively close to existing stub-ups.
PRO
Charles Ross Homes
last year
I appreciate the desire to recycle any portion of the existing home; it's good stewardship of resources. That said, the constraints of the existing slab and utilities is likely to result in added cost and added risk to the construction of the new home. Remove it and start over.
PRO
Patricia Colwell Consulting
last year
I see no benefit to trying to design a house around an existing foundation and I have to agree that plumbing will all need to be brought up to code for sure . I hate crawl spaces they are like 1/2 a basement that you can't access for anything .I love bedroom wings but not bedrooms at the front of the house for sure. IMO the foundation is driving the design insted of the design driving the foundation
PRO
Mark Bischak, Architect
last year
Demolish and remove the entire existing structure. Who knows, you might find Jimmy Hoffa under there.
just_janni
last year
Saving stuff always sounds good at the start. Them, you get into things and realize it's more work, more money, poorer result and, as noted - 70 year old materials.

Dig it up - get to compacted solid ground, insulate and having something for the next 100+ years.

Like your rendering!!!
James Hounsell
last year
looks like the consensus is that it will be problematic and costly. Time to demo and start with a new foundation. Thanks everyone.
dan1888
last year
If the plumbing is cast iron, it's likely rotted out. If it's pvc, do a camera inspection. You must like the location. That house doesn't look outdated. It would sell if updated.