# 1/2" basement slab



## Golden view (Feb 16, 2012)

You read that right. 1/2" thick. Under contract to remodel a basement, was going to grind floor for a salt and pepper finish, but discovered it's basically nothing. Thickest portions range up to 2" thick, but most are less. Easy to smash any portion with one swing of the sledge from my hefty 160 pound frame.

Funny thing is it's the second house on the same street where I found this. 1920s homes. Now worth $700-1mil.

Anyone ever encountered one so thin? 

Anyway, looks like this week we're setting up the conveyor, busting up a slab, digging down, and pouring new. Yehaw!


----------



## griz (Nov 26, 2009)

sounds like a rat slab.


----------



## NJ Contractor (Nov 12, 2016)

Found the same thing a few weeks ago in a portion of the basement of a 1920's multifamily rental I own, while trying to remodel the laundry room. 

We did what you are about to do - removed the slab and poured a new one with gravel and all...good times. We were able to shoot the concrete through a window. It's never easy.


----------



## Tinstaafl (Jan 6, 2008)

Well, at least the demo should be relatively easy.

I've seen a couple like that, but not common at all.


----------



## donerightwyo (Oct 10, 2011)

Hauling materials in a wagon and mixing by hand, I bet it would be easy to convince yourself a 1/2" was plenty good enough:whistling


----------



## Morning Wood (Jan 12, 2008)

Never 1/2". But definitely 1-2" yes. Did a slab last fall that we dug up and did gravel, foam, poly. It only ended up 1/2" thick in spots above footer because original footing and wall were so crappy


----------



## Golden view (Feb 16, 2012)

I can't believe it's held up for so long (maybe not as old as the house). Checked records, this house is 1911, other one was 1912.

Demo should be easy. Will use a line pump for the new slab.


----------



## greg24k (May 19, 2007)

Morning Wood said:


> Never 1/2". But definitely 1-2" yes. Did a slab last fall that we dug up and did gravel, foam, poly. It only ended up 1/2" thick in spots above footer because original footing and wall were so crappy


Yes, 1 1/2" was always the usual norm for a rat slab. In the earlier days, the guys would use a 2x on the flat and bring concrete to it, I saw them do that mostly in crawl spaces, but in 1900's they did the basements with a rat slab.


----------



## Morning Wood (Jan 12, 2008)

Usually when redoing slabs there is also concern for ceilings my height and when you add in foam and wire in the concrete you end up having to go down


----------



## superseal (Feb 4, 2009)

I never seen specs. that didn't require a rat slab in a crawl...


----------



## ECS_Ecentric (Jan 18, 2017)

Golden view said:


> You read that right. 1/2" thick. Under contract to remodel a basement, was going to grind floor for a salt and pepper finish, but discovered it's basically nothing. Thickest portions range up to 2" thick, but most are less. Easy to smash any portion with one swing of the sledge from my hefty 160 pound frame.
> 
> Funny thing is it's the second house on the same street where I found this. 1920s homes. Now worth $700-1mil.
> 
> ...


I may have to make time to go look at the work you're doing. That sounds like a good puzzle to solve.  

Sent from my LG-H918 using Tapatalk


----------



## Golden view (Feb 16, 2012)

superseal said:


> I never seen specs. that didn't require a rat slab in a crawl...


Well that sure would make them more pleasant to work in. I've never encountered one in a crawl in the Pacific NW.


----------



## Xtrememtnbiker (Jun 9, 2013)

Golden view said:


> Well that sure would make them more pleasant to work in. I've never encountered one in a crawl in the Pacific NW.


I'm in Virginia and never seen it either. Agreed, it would make it much more pleasant for sure.


----------



## overanalyze (Dec 28, 2010)

The only time we have done rat slabs in our crawls are when we are close to the lake. 6mil vapor barrier and crushed stone are what our new crawls get. 

Sent from my SM-T310 using Tapatalk


----------



## builditguy (Nov 10, 2013)

I see 1/2" slabs all the time, in houses earlier than 1920. Often I will see a thin layer of concrete over bricks, laid flat. No mortar, just laid in place.

I think it was an upgrade, over time. I think alot of houses had dirt basements. Then someone got fancy and laid brick in theirs. Of course everyone had to keep up. Then down the road, someone poured thin concrete over the brick, just to clean it up. I think the concrete was usually in the 40s or 50s. Depending on how high class you were.
This is my opinion only, from being in alot of old houses and commercial buildings.

Regarding concrete in the crawlspace, I think I am the only one in my area that does it. Years ago, people thought I didn't know what I was doing. They regarded it as a waste of money.
Usually when someone sees me do it, their first thought and question is, "What do you think you are doing?" When I explain it to them and point out the actual cost difference, they change their mind.


----------



## hdavis (Feb 14, 2012)

For a very short time, some people would just put dry Portland over a sandy basement, mix it in, vibrate it, and water it.

Just in case you come across a crumbly mess.:whistling


----------



## Golden view (Feb 16, 2012)

Took it out today. Crumbly mess. 1x1' pieces would break in half sometimes in your hand.


----------



## philcav7 (Jan 15, 2009)

builditguy said:


> I see 1/2" slabs all the time, in houses earlier than 1920. Often I will see a thin layer of concrete over bricks, laid flat. No mortar, just laid in place.
> 
> I think it was an upgrade, over time. I think alot of houses had dirt basements. Then someone got fancy and laid brick in theirs. Of course everyone had to keep up. Then down the road, someone poured thin concrete over the brick, just to clean it up. I think the concrete was usually in the 40s or 50s. Depending on how high class you were.
> This is my opinion only, from being in alot of old houses and commercial buildings.
> ...



That's what I have in my basement. 

Dirt floors were quite common in old homes with stone foundations. Bricks were added to keep your feet out of the mud. Odds are the concrete was added after a much later date than construction. 

Mine is cracked and crumbled. I may get around to pulling the brick and pouring in a 2-3" slab over plastic. Maybe someday.


----------



## DaemarConst (Aug 13, 2016)

Demo existing slab, excavate 8 inches and pour new slab.


----------



## Irishslave (Jun 20, 2010)

Look at it this way if your putting a bathroom in the waste extensions should be a piece of cake


----------

