Horizontal cracks in basement walls

[Hhali]

Hi, I have a question for all the structural engineers here. I am in the process of buying a house and the listing agent just disclosed to us that the house we are interested in has a horizontal crack in one of the basement walls, she blamed it on the water pressure in the subdivision. Is this a problem that can be permanently fixed ?should I not consider buying this house? Thank you.

 

[dik]

Horizontal cracks can be a big problem, in particular if they are located near mid height. It's a matter of determining why the crack formed and what the wall reinforcing is. You might want to check with a local engineer or soils guy.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[1503-44]

You don't want cracks in the basement anyway, but especially those that may have been caused by "high water pressure in the subdivision". I don't think she meant "at the tap".

I'd tend to regard any fix as "temporary". Water has a way with getting through normal concrete.

 

[BAretired]

I agree with dik. Determine the cause before you buy.

BA

 

[bones206]

It's definitely a red flag. The fix will probably include some combination of: high performance perimeter drain, sump pump, exterior waterproofing membrane and drainage mat, helical tiebacks, strong backs, crack injection, etc. All expensive propositions but there really aren't any cheap fixes for this problem.

 

[1503-44]

And next, after you fix the wall, keep your eye on the basement floor. Water pressure just attacks the next weakest point remaining.

 

[StrucPatholgst]

My two cents: In my area (NJ) a horizontal crack in CMU joints at or near the grade line typically stems from from either freeze-thaw action of moisture-laden surface soils (poor drainage), or damage from compaction (paver patios, etc.). A horizontal crack in CMU joints half way up (or less) from the slab to the top of the burden (i.e. grade), is typically due to moisture-laden soils through the full height of the burden. Tree roots can also cause horizontal cracks.

A number of repair methods are mentioned in this thread. I'll mention one more, even though I don't ever recommend it: carbon fiber straps. Reasons why I don't like carbon fiber: 1) it relies too much on the bond strength between the CMU and the fiber resin (if you have crappy CMU, you have a crappy bond); 2) the contractors that install them tout the strength of the fiber, and don't talk about CMU condition; 3) it is a known and studied fact that the quality of the resin bond differs between the CMU surface and the grout joint surface; 4) the warranties (and I have seen many) make it clear that any moisture in the foundation masonry voids the warranty.

With all that said, I just looked at a 20 year old carbon fiber job, and it's holding up nicely. But there is no plan B when a carbon fiber job fails. The next step is foundation wall replacement.

Regarding your concern over purchasing it or not, that's a value decision, but personally I would have no issue with a horizontal crack so long as certain parameters are met (extent of cracking, leaning or bowing, signs of moisture penetration, etc.).

 

[XR250]

But there is no plan B when a carbon fiber job fails. The next step is foundation wall replacement.

There is plenty of plan B.

Soldier beams
Construct a 2x8 stud wall in front of the CMU
Helical tie-backs

FWIW, I have only once seen a CF job fail when the contractor did not grind the paint off the wall.

 

[HouseBoy]

It's been a few days since you first posted so maybe this is too late but...
Horizontal displacement (bowing or leaning) of the wall would be an important observation to measure with a 4 ft level or a plumb line.
I don't see whether the wall is CMU of cast in place concrete but that would possibly affect the "severity" of the problem and recommendations and/or methods of repair.

Generally speaking - a horizontal crack in a concrete wall is often related to a rusting rebar, perhaps the concrete had calcium chloride in it.

One other thing about CF - I THINK that the CF design code (forget the exact acronym) says you can't use it if the stress in the wall is greater than 50% of allowable (or something to that effect).

Simpson Strong-tie has a real good webinar about CF products and they are strong supporters of that provision. Some (many) basement wall repair companies appear to disregard it.

 

[BAretired]

Sometimes, the wall bows inward without cracking, or was not built plumb in the first place. I have found a straightedge works quite well in measuring the crack width by taking an offset measurement. (see below)

BA