Bulging Concrete Block Basement Wall 18

[jcali]

This seems to be a common problem in residential construction. A concrete block basement wall that is cracked horizontally (mid height) and bulging inward, obviously due to lateral earth pressure with inadequate or no wall reinforcement. What is the state-of-the art way of repairing this? I'm looking for a solution that spares the home buyer (or seller) from an extensive and costly wall reconstruction project. Any ideas or success stories would be appreciated.

-JCali

 

[boo1]

check guides at site:

http://www.ncma.org/etek/homefrm_map.cfm?spdm=cemexusa.com

 

[WHEngineer]

Just a note - we see these problems often in the SE. One of the more common repairs is the installation of soldier beams consisting of two back to back sections of C5x9 channel separated by a 2"x4"stud. The top of the channels are cross-bolted through the joists while the bases are connected to the floor slab with 3 inch angles. We have found that the beams should be set on maximum 5 to 6 foot intervals to prevent bulging between soldier beams. This method works well when horizontal wall deflections are less than 2 to 3 inches. In situations of greater deflections, helical tie-back anchors are run through the soldier beam.

This much said, the repairs are generally band-aids that don't address the actual problem. In most of these cases, the backfill against the foundation wall was improperly compacted and has settled over a period of years. This results in negative drainage toward the foundations and a build-up of hydrostatic pressure against the walls (note that the bowing walls often coincide with damp or wet basements). In order to fully correct the problem, exterior drainage must be controlled and re-directed away from the foundations. By the way, recent codes have addressed some of the foundation problems by requiring reinforced foundations for unbalanced fill foundation walls.

 

[PEinc]

WHEngineer,

Since the wall is bulging inward, it will probably be bearing on your double channels in only one location. Do you require that the gap between the wall and the double channels be filled with shims or grout in order to provide continuous bearing and support?

 

[UcfSE]

I think it could be worth while to investigate the use of a fiber reinforced polymer (frp) bonded with epoxy. The frp comes in cloth like sheets and is applied similar to wall paper with epoxy. This method is used to retrofit concrete columns and bridges but I don't think it would be too difficult to adapt for your needs. I don't have any experience with this, it's just an idea so I can't say how well it will perform or even if its a good way to go. If it were my house I would at least check it ou tthough. It would be easy to apply, you wouldn't need to demo anything major and it wouldn't add a signifcant amount of depth to the wall. Fyfe Co, LLC is a company out of California that manufactures these product and may be able to give you technical advice on the feasibility of using it in your basement. Here's a link to their website:

http://www.fyfeco.com/

Good Luck!

 

[jcali]

Following up -

How do you install a vertically reinforced masonry basement wall under an existing wood frame superstructure wall? How do you get the rebars in and build the blocks around them? Or, how do you build the blocks and then insert the vertical bars?

JCali

 

[jheidt2543]

Here in town an existing two house was moved onto a new lot. The house was set on cribbing and the basement footings, slab and block foundation wall built under it. Once the reinforced block wall reached it's full strength the house was lowered on to it. It is actually not as difficult as you might think, however it was an experianced house moving contractor that did it. This is not for the "weekend mason" to try.

 

[UcfSE]

One way to get the rebar in the wall:

Place the full height vert. rebar in its location complete with hook at top if required. Cut the head out of some units so that the cell to be grouted can fit around the rebar. This is not the same as cutting the end out of the unit which would make it 2" short. Do this all the way up, just at each bar location and cut the face out of the bottom unit for a clean-out. For the lintel, lay several block along the course and slide the reinforcement in from the end of the last unit. Keep going down the wall. Before you get to the last few slide the remaining rebar into the lintel course and as each of the last units are placed keep bringing the rebar forward. At the last one slide the rebar into its final position which should lap a bar grouted into the existing masonry or concrete if it's there. Cut the final lintel block deeper and work it under the rebar and into place, or cut it in half and bring the 2 halves together around the rebar from each side. This may or may not be necessary at the first one or two lintel block. The block at the top will need some cuts to allow a pump hose to fit along with some cuts in the lintels as necessary so that the wall can be pumped.

This can be done easily by regular crews with no special lifting of the house. Saws are very common on masonry crews. In fact, if the crew doesn't have a saw, that's a hint that there is something wrong whether they are too cheap or not as skilled in their work. Saw cut units reflect crews that take the time to do a good job and care about the final product of their work plus it saves the integrity of the block from being compromised by hammer-cuts. Years ago special saw cutting was considered too expensive and still shoul dbe avoided if possible. Today's houses are however much more complex then those that used to be built and saws and saw-cuts are an everyday occurance.

 

[boo1]

this months Journal of Light Construction has an article on this subject.

 

[Slowzuki]

We have built several dry fit block walls using a structural skin product to bond the outsides of the blocks. This may be suitable in some cases to apply on the inside surface of a failing wall to prevent further movement.

 

[RVSWA]

I recently bought my first project/venture house about 6 months ago. It had a 6 foot daylight with a 6 inches thick, non-reinforced wall. The ACI has about three really good publications on Shot Crete or Gunnite (both correct and interchangeably used). I had the house lifted 3 feet in the air for $10,000, finding a good house mover was not really easy but not terribly hard either. To get a recommendation on a Gunnite contractor, I called a local ready mix plant that I have frequently worked with to give me a recommendation.
My wife and I bent and tied a mat of reinforcement to the inside face, about 2" off the old concrete wall, hooked and epoxied into the base of the wall and terminating in the upper portion. Plywood was nailed to the rim of the raised house and the sill plate with anchor bolts already in it was screwed to the inside. The Gunnite was shot in about 4 inches thick over the old concrete wall and of course about 10 inches thick at the two foot void created by lifting the house. The Gunnite cost me $3000 for material and labor. An important point about Gunnite, I used #3@6"o/c vertically to give the Gunnite something to hold on to vs. a large bar with a bigger spacing. My contractor didn't like the idea of Welded Wire fabric but I'm not convinced that it couldn't be used in this application. The bonding of Gunnite to existing block or concrete can be surprisingly strong however a good attachment at the top and bottom would still be prudent. I think this idea could be adapted to a failing block wall; the prices were for 2004 in the Seattle area if that helps.

 

[mzoc]

Try this site for info.

http://www.e-foundationrepairs.com/

 

[Rich2001]

Here are a couple sites, utilizing a carbon fiber epoxied to the cmu wall

http://fortressstabilization.com/

http://thereinforcer.com/