Cracked slab foundation concern

robert pahel · 06-10-2012, 06:43 AM

I am finishing my basement and after moving some carpet squares im worried that this crack in the slab foundation of my house has some for thought for concern. its raised from the corner of the sliding glass door and gradually cracks and levels out to the middle of other side of the house by the HVAC. Behind the HVAC the wall holds a large steel beam spanning the whole inside of the split foyer. Any insight on this would be greatly appreciated!

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**Jim Luttrall** · 06-10-2012, 07:40 AM

I would recommend hiring a home inspector to see this in person. It might be something with no cause for alarm or it might be something that is an indicator of larger problems. There is no way to diagnose the problem here with just a few photos and a (no offense) novice on site. There are likely other problems that would make the hiring of an expert seem like a bargain; such as the possibility of a return air grill located in the same room as a furnace combustion air inlet. Please hire an expert to guide you.

**Jerry Peck** · 06-10-2012, 08:10 AM

Robert,

Concrete does two things: 1) it gets hard; 2) it cracks.

That said, there is more than just a crack shown in your 3rd photo, there is differential settlement (one part moves in relation to the other part) as shown by one section having settled down in relation to the adjacent section.

If you lay a level on the higher section, adjust the level to read level, how much difference in height is there down to the lower section?

If you lay a tape measure across the widest part of the crack, how wide is the crack?

**John Kogel** · 06-10-2012, 08:58 AM

Two more things - how old is the concrete basement floor, and are there any foundation cracks visible around the perimeter of the house?

**Eric Barker** · 06-10-2012, 03:13 PM

Originally Posted by John Kogel

are there any foundation cracks visible around the perimeter of the house?

That's the question I'd be asking. Most likely the floor slab is separate from the foundation - the floor's settlement may have absolutely no relationship to the load path (bearing) components of the home. In my experience, what generally happens is the floor cracks are due to uneven settlement from uneven compaction of the surface under the slab. In such cases it's not much of a concern and if desired, the dropped section can be raised back up in alignment with the rest of the floor. As John said, what's the foundation look like?

**Joseph Ehrhardt** · 06-10-2012, 07:55 PM

Look where the crack leads you, right to the corner. Looks like no expansion joint around the perimeter. That floors placed keyed into the door way where as the foundation block should of been continued across, thats why we have 4" inch pancakes, could be other issues, but thats one from the photos supplied

robert pahel · 06-11-2012, 07:29 AM

the house was built in 2006 as far as the outside foundation there is only mild hairline cracks in some spots less than a 1/16 of an inch if that. however the there is a spot by the sliding door where the outside foundation might have slightly moved outwards because the sliding door has separated slightly from the cinder block foundation i canh take a pic when i get home this evening. on the other corner of the house on the parallel to this crack shows where the slab has slightly dropped a inch or more in the corner because the nail from the foundation to the slab that was embedded has broken loose from the slab with a small piece of the slab still attached and the slab underneath that part is hollow when i smack the slab with a two by four i can feel like slab vibrate in the corner

robert pahel · 06-11-2012, 07:31 AM

is realigning that piece of floor an expensive fix?

**John Kogel** · 06-11-2012, 11:42 AM

Originally Posted by robert pahel

is realigning that piece of floor an expensive fix?

It could be. You need a professional to look at the foundation and the floor and he will make a decision as to whether the movement has stopped. It seems that the foundation has sunk at least a bit on the right side, pic 1, where you say there is a gap at the door frame. and you say there is an inch of slab settlement on the other side of the house.
Do you have good gutters and drainage all around the exterior? Moisture around the foundations can cause things to sink. Maybe all the movement occurred in the first year.
Don't cover anything up until a professional has looked at it.