Hearth pulled away from fire place or vise versa.

+1

My brother has a 1950's ranch. Raised brick hearth was built up on lumber from below in the basement. It settled over the years and had to be re-pointed. Chimney is in the center of the house though. No issue now, but it may need a re-point in a few years.

BeGreen said:

If this is recent, look for insect damage in the support. If directly on the slab it may have cracked due to lack of reinforcement. If there has been no change for years, I wouldn't worry too much about it.

Click to expand...

While I generallyagree with BG's commrnt above, I would think you still should tuck point the space. You don't want a hot coal dropping down in there.

One of my chimneys has settled back a little as the foundation has moved. Keep an eye on it. Depending on your foundation, you may also have a little frost heave - my deck moves because they didn't dig the foundations deep enough.....

You can buy a "crack monitor" to find out if it is moving still or if that is it. You can find them doing a Google search, they are very helpful.

Put a level on the hearth and chimney. If the chimney is out of plumb that's your problem. If the hearth is out of level than it has settled.

Heartily agree with the crack monitor. Start a little log to go with the crack monitor. Get some monitoring points including plumb readings on the masonry. Record data once a month for a year or two. Note any water or weather issues.

As I understand your post, the house is slab on grade and the chimney is on a slab foundation. Extreme weather may cause soil motion that doesn't normally occur. This link is to the soils map for a plot of land in Osage County, Kansas. http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx(that session just expired)
You can see the spot I picked has poor soil for a slab on grade foundation. You can check the soil on your property at the same website. This is only a general idea, but if you find your soil is marginal for a slab on grade, perhaps you will have an understanding of what might be going on.

Just continue to monitor and seal cracks with a flexible sealant. After spring thaw, go around the area of your chimney foundation and slab and compact the soil tightly. Add more soil and create a high spot next to your house. This should help keep the under-slab soil moisture constant. If soil moisture stays relatively constant, the soil will not expand and contract and your motion should cease until the next extreme weather year. Which could be twenty years or two years.

If the soils map shows you have soil that is susceptible to freeze thaw, consider going vertical down the slab edge a couple of feet with some R-10 insulation installed appropriately for your climate and termite conditions. This should keep freeze thaw from moving things around. Actual R and depth would depend on your location. Generally a water source within 25 - 30 feet depth with certain silty soils facilitates freeze thaw. The silt draws the water up by capillary action until it reaches the frost line where it add to the ice lens. The ice expands and pushes up, then melts and leaves a void in the thaw. Plays heck with shallow foundations. Local experience trumps anything I may say.

If your monitoring program doesn't reveal much more movement, or indicates cyclical movement, you probably can live with it for many years. Especially since you will have the peace of mind of actually knowing how much things are changing. If things get to going one way and don't stop, have a few people look at it. Have more than one company give you a diagnosis and a written quote. There are many people in the foundation repair business that may not know what they are doing. Be sure to check references, the local BBB, and the local code agency if you have one. The local Soil Conservation Service office may be able to give you some help, especially if you live on a farm. Kansas has an active university outreach reputation. Perhaps there are some good references on-line or in your local government files. It is highly likely that others have had your problem in your area and good solutions are known. If you have a neighbor that is a farmer, or one that works for the highway department, you may have the best expert on the soil at your location that exists. All soils are local and the best soil experts are often local people with bright minds and jobs that bring them in contact with soil problems.

Don't panic. The leaning tower of Pisa was built about 800 or 900 years ago and it still stands.