I am thinking of using almost a second vapor barrier on basement walls 4

[VaporBryan]

I just bought a bungalow built 1960 up north. The basement walls are cinder blocks. They are damp. I am thinking of breaking the slab on the inner perimeter and installing a french drain pumped out by a sump pump.
I am thinking of placing a vapor barrier on the cinder blocks (because they are so damp) From the top to the bottom of the french drain. I am then thinking of finishing the basement. Using wooden 2x4" and pink fiberglass matts covered with drywall. Since the vapor barrier should be behind the drywall, I am thinking of placing a second barrier there. Both barriers will drain into the french drains with spacers. The french drain would be covered with cement except the two spacers which will allow each barrier to individually drain. Both barriers will be sealed at the top and open bottom to remove trapped moisture. I think??

 

[SteamBryan]

a2mfk,
Thanks for the info!
I am doing it in phases.
1- Fix surface drainage. + Start straitening the wall. + test for Radon.
2-examine Radon results.
If high, go the above epa route.
If low:
A- go with Vapor barrier against wall ending in French drain. I will have drilled holes in the bottoms of the bottom blocks. The above sketch is good.
(slab same level as footing). So water coming out of those holes has to be routed to the French drain.The vapor barrier would do the trick?

B- Modify epa system so the holes can drain. ie: start the barrier only inches above the hole and install the flute spacer for access to the French drain.

C- something I have not thought of yet?

Best regards,
Bryan

 

[TXStructural]

If you have cut the slab away from the wall, PUT IT BACK. <wink> It more than likely restrains movement of the wall into the basement. Not having it in place takes away the support the wall "expects". This might not be the case, but I suspect any footing under the wall (if the slab isn't the footing) was not designed to resist sliding of the wall under full soil pressure. And unless it is properly doweled into said footing, it might just slide off.

To satisfy my of morbid curiosity, can you give us an idea of how out of plumb or out of plane the walls are? Is it bowed two inches over 30 feet of length at the top of wall, bowed in two inches at mid-height everywhere, or does it lean in two inches from floor to ceiling?

What is next to the house? You say you have six feet to the property line, and I'm curious what is next door that could be a) dumping water onto your property (like the lot next to my house that sheds to my yard, and mine to the house downhill from me), or b) is there a huge pile of dirt/big building pressing down on the soil mass against your wall?

We might offer solutions based on these answers. But expect us to direct you to a local structural if it sounds like you need one. (You ALWAYS need one.)

 

[oldestguy]

Bryan:

Short answer. The buried foam should do the job. However,if problems are not all fixed, the surface work can come later.

 

[SteamBryan]

TXStructural,
bowed in two inches at mid-height everywhere, basically the full length of three walls. It is out of plum buy 1 to 2 inches.
The next house is 12 feet away. It is about 3 feet higher on an even slope. next door is dumping water onto my property.

Oldestguy,
Thanks again.

Regards,
Bryan

 

[oldestguy]

If you are doing the buried insulation job, can you shape the final surface so as to have a swale at the PL?. It should help a lot. Sounds like tight quarters and a difficult job.

Bracing the wall takes consideration as to the top of wall situation. If it is not a bearing wall, that may explain the out of plumb. Any brace has to have a resistance up there and a non-bearing wall has little. The earth anchor alternative may be best and least complicated. That anchor needs to be beyond the zone of influence on the wall or it is like the boot strap analogy.

If bearing wall appears not fully capable of resisting the bracing load, add scabs under the joist ends (planks between the wall blocks (not only the plates) and the joists,). Do this at opposite ends of the house using the first floor as the strut.

 

[SteamBryan]

Oldestguy,
Thank-you once again!
I am over 65 with a bachelor's and recently retired. I am OK with thermodynamics but forgot anything I knew about Vapor Pressure. Your help is greatly appreciated.

On the property line is a set of cedars. I have to build up to have a downward slope so much that I do not dig. At the property line, I am thinking of making the middle of the house the high point and I was thinking of sloping such that the low points are 10 feet away from the building. Since I cannot dig at the property line without cutting the roots, I think the swale would have to be a solid material? The insulation would end on top of the swale. Therefore, the cover over the insulation near the swale would be about 4-6 inches. At the swale I would cover with 3/4 inch gravel. Is this what you seem to be suggesting??

The bow is V shaped. The top and bottom of the walls kept there position. I do not understand how a basement wall of a bungalow can not be a bearing wall, according to my definition?
Earth anchor is not possible with only 6 feet distance?

I do not understand your scab. Are you referring to joist as planks? are wall blocks the cinder blocks composing the wall? Are plates the sill plate?
I am placing a wooden brace at every joist.(16 inches) there will be a brace at the opposite wall of the joist.

Best Regards,
Bryan

 

[oldestguy]

Brian:

I think you have it.

I made a rough sketch of it called Wall Brace.

A bearing wall is the wall where the floor joists sit. That load is very useful in keeping the blocks from caving in. It does so by downward loading, as well as friction on the top of wall. An example of this downward load effect is take a stack of kid's toy blocks and carry one end in your hand with the other hand pressing the stack together. You can do all sorts of configurations with your two hands pushing together and the blocks don't fall. It is that compressive force that counters the tendency of the wall to cave in. However, the main thrust of my statement is that the joists sitting there also make a place for adding some resistance to prevent top moving in, in addition to the frictional ability of those joists and the plate (sill plate). So if you have light load, as where there are no joists, the downward compressive force in the blocks is much less, making the ability to resist caving in much less. There also is much less ability of the house above to resist that tendency for the wall top to move in by friction on top.

So at that lightly loaded wall, a good resistance to the top moving in is not there. How to add resistance there becomes more complicated. What is desired is to get that inward push tendency somehow into the floor system. Bridging between joists helps, but conventional bridging probably is not enough. Solid bridging is better. Many builders just take the same size plank, cut 14-1/2" long pieces and use that as bridging material. Braces have to reach to the block, not just to the sill. Double thickness plank is needed. Where I have done this, I use 2 x 4's and 2 x 6 with pole barn nails. By the way, I still am older at 85.

 

[oldestguy]

I should add where you have an interior beam supporting the joists, that beam does the same thing at it's support. However its effect is limited to the part of the wall it sits on. The beam has friction resistance sometimes. But, too often it sits on blocks of spacers, etc. So that also should have some form of scab to apply solid resistance to the wall top moving in. Check how it might transfer its resistance to move. Generally that is up into the floor system. The far end also may apply some resistance. A steel I beam probably will take some drilling and bolting of an angle clip. Where basements have caved in, these beams punch out through the wall.

 

[SteamBryan]

Oldestguy,
Thanks again,
Two of the three walls are bearing walls. Now, I understand what you are saying. Makes perfect sense.
Regards,
Bryan

 

[a2mfk]

Two inches of deflection in a basement wall that is likely only partially reinforced CMU is rather significant. I'm a structural engineer who regularly evaluates CMU and I am surprised you are not having all kinds of cracking. As previously stated, you need to have a structural engineer evaluate this and help you with the repairs. This is not a problem to just rely on message board advice and do-it-yourself. I can appreciate your DIYer mentality, but this requires actual engineering, and you being one yourself I am sure you can appreciate that.

Here is another article about moisture and basement walls:

http://www.buildingscience.com/documents/information-sheets/basement-insulation?searchterm=basement

 

[oldestguy]

a2mfk

Interesting comment. Trouble is the walls are masonry block (he calls them cinder block). Pretty hard to do much structural calculations when you are just dealing with a bunch of individual blocks( probably not well glued together). When I was a kid they were cinder blocks made with coal ash cinders. For 1960 vintage I suspect they are of concrete. Still, since the original job likely was by amateurs, the mortar strength also might be questioned The structural part comes from transferring the earth pressure loads into the building and considering the wall as not much of a help. However, if the outside buried insulation work and better surface drainage comes about, it would be expected that frost action, pushing in the walls, would be less or not present. Then, just keeping things as found probably is the best that can be done, short of completely replacing the wall system. Of professionals, I'd guess a good carpenter would be the best fellow to have there. Earth pressures could be calculated, but I doubt that any of the constructors who do wall bracing do any calculations. lacking knowledge of what Mr. frost can or will do, a guy has to do the best he can. I don't know of a way to figure frost heave pressures that means anything. Earth loads yes, but not frost. Maybe someone can jump in with that.

 

[SteamBryan]

Well,
I'll bring in an engineer for a visit and verbal advise.
His gut feel is worth the price.
Regards,
Bryan

 

[a2mfk]

OG,
Sorry I have to strongly disagree with you on this specific point. Structural engineers are not just here for new buildings, we work with rehab and renovation of historic structures all the time. There are lots of options and methods for strengthening older partially or unreinforced CMU walls, but you should not just experiment as a DIY'er or trust that a carpenter can understand the forces and stresses involved.

Since Steambryan said he is hiring an engineer, I will leave it at that. Get to the bottom of your drainage and soil problems, and then fix the wall. Hopefully some of the "bow" will go away once you have improved the site and soil conditions.


Good luck!

 

[oldestguy]

a@mfk

OK, let's see what the engineer says. Interesting how this thread has progressed from a simple question to a complicated thing. I still doubt that much of any new ideas will come forth, since the pushed in block walls are very common and the contractors that brace them don't engineer much of anything, other than to find "they work". Other than replacing fully caved in walls,I don't know of any one that has "pushed them back". I do recall one bridge job however, where compacting the heck out of backfill to a new bridge abutment that sat on piles caused the abutment to be pushed toward the lower roadway about a foot. They dug out the fill and some from the timber piles and pulled the thing back. Used a dozer and a grader with cables. Yes, the piles bent some first and came back straight. I would bet the "powers that be" didn't know of that. I was there for something else and just kept my mouth shut. No problems after that. No engineer involved (other than me). At this site, I suppose you could do the same thing. If it was my house, I probably would. But, I'd want to be on site for such a job.

 

[SteamBryan]

I have had an engineer examine the situation. He said everything I am doing is very OK.
He said I could use a breathable material on the inside brick wall. (waterproof but not moisture proof)
Best Regards,
Steam Bryan