Jump to content

When to call in a geotech


Recommended Posts

Inspected a 1950s 2 story house on a more or less level site. Crawlspace construction with a poured perimeter concrete foundation wall.

From the interior inspection it was obvious that some settlement had occurred with the back half of the house. From the exterior I found a pretty large 1/2" crack midwall on the south side of the building but from the crawlspace the foundation was actually cracked pretty much at every discontinuity ( crawlspace access, foundation vents, girder pockets etc.) The form of the cracking indicated settlement vrs shrinkage or thermal cracking.

I have seen this situation more than once. I can see recommending further evaluation by a geotech when there are obvious problems with the ground like subsidence and fissues etc. but this looks like to me to just be an improperly prepared site.

If the clients asks "Is it going to settle more or is it done?" How would you answer that?

They tried to level the floors by shimming the sill plates and even individual joist ends. Note no anchorage is present. Floors are bouncy as hell. Are we looking at needing a new foundation?

Chris, Oregon

Link to comment
Share on other sites

Hi,

You're first sentence pretty much is the diagnosis.

A level lot is as bad as a lot that's graded toward the house. However, if the settling is consistent and shows no sign of recent changes, I certainly wouldn't recommend replacing the foundation. Hell, those footings have had over half a century to reach final compaction, if you replaced the foundation without improving drainage the same thing is liable to occur.

I'd tell 'em to talk to a reputable/competent foundation contractor about what it will cost to inject the cracks with epoxy. Do it right, and the repaired cracks will be stronger than the foundation.

Just don't forget to get the exterior drainage improved and ensure those downspouts are discharging at least 6ft. from that foundation.

ONE TEAM - ONE FIGHT!!!

Mike

Link to comment
Share on other sites

I have to agree with Mike. The primary source of foundation issues in my area is poor site drainage. Nearly every report I write indicates that site drainage should be improved. As Mike said, the foundation has had a long time to settle, and probably won't go much farther if properly dealt with and the site drainage is improved. However, repairing the foundation may be futile without the drainage improvement. Both are required to reduce the potential for any further movement.

Link to comment
Share on other sites

What about the top of the foundation? Now that sections of the cracked foundation have settled unevenly how do they get the sill plate level and anchored if one wanted to level the floors and get rid of the bouncyness?

Level the sills then pack the gap with cement? Replace sills with sill beams?

Also concerning the epoxy I thought that was for sealing rather then structual restoration. Are there epoxies out there that can essentially glue the sections back together back into one cohesive unit?

Chris, Oregon

Link to comment
Share on other sites

Hi,

Well, you didn't say how much height differential there was in the walls. They rarely shim them around here if they're less than about 1/2 inch because it usually isn't that noticeable inside the home. Of course, though around here about 90% of them have at least one vertical crack without any differential settling, most of those with differential settling are pretty old and folks come to expect uneven floors in those old homes.

There's about 4-5 ft. of soft glacial till here before one starts hitting bedrock and really good bearing soils, so it's prevalent with the old bungalows around here. Hell, when I find one without a cracked foundation and nice flat floors with square doorways, I'm immediately suspicious that it's either had a new foundation placed underneath it or the house or had been lifted someplace else, put on steel, brought there and then set down. Seem to find my fair share of those.

I did have a doozy about two weeks ago. The entire south half of the foundation had cracked and settled on a 1930's brick veneer tudor. The sills on that entire side of the foundation were shimmed up about two inches. Don't even get me started on the condition of the veneer.

OT - OF!!!

M.

Link to comment
Share on other sites

What is the best practice method to level out the sill plate on a settled foundation system in excess of 1/2". For example or the order of 1" to 2".

It can't be to shim it with dispersed wood shims. The space between the sill and the top of the foundation wall wood have to be continuously shimmed or filled with something. Right?

Chris, Oregon

Link to comment
Share on other sites

Hi,

If it's that much, you could a 5/4 or a 2x under the original sill. Or shim it at intervals - I dunno - every 16 to 20 inches - and then grout the gap between the top of the foundation and the mudsill with a really stiff mix.

Or, just say,

"The foundation wall at X has cracked and settled substantially. Have a competent foundation contractor, working under the direction of a licensed engineer, repair it as appropriate," and stop worrying about how to repair it and simply report it.

OT - OF!!!

M.

Link to comment
Share on other sites

If the clients asks "Is it going to settle more or is it done?" How would you answer that?

The answer to that question is unknowable. To find out, you'd have to slap some crack monitors on the foundation and document their movement for a year or two. The resulting data will answer the question.

They tried to level the floors by shimming the sill plates and even individual joist ends. Note no anchorage is present. Floors are bouncy as hell. Are we looking at needing a new foundation?

The home inspection fee covers finding problems, not solving them. If I found something like this on an inspection, I'd kick it over to Jay Kushner at Seismic Technologies (283-8337). He solves problems such as this one for a living.

- Jim Katen, Oregon

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...