Thread: Information Request

A group of Chicago area inspectors met the other night with a reporter for our local public radio station; she is trying to help inform her listening audience about the moisture intrusion problems that are rampant out here with masonry construction and in particular with single wythe concrete block exterior walls. She asked if we could help her find out whether other areas of the country are experiencing similar problems and, if so, what steps the local code authorities may be taking to address the issues. Any help you all could provide would be greatly appreciated. Thanks in advance.

Dan

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Nearly all concrete block foundation walls I see have some level of moisture penetration. The blocks are moderately porous and not watertite by themselves from my experience.

What type of issues are going on in Chicago Dan? Is it something out of the norm or extreme?

I assume this is commerical construction, I have seen any block homes built in years. Or is chicago different?

Yep, raw CMU block soaks the water like a sponge. It seems like split/chiseled face is worse when it comes to allowing water in.

There are thousands of CMU houses built, of all ages, with only paint on them, and NO moisture intrusion issues.

It's not "the block", it's "the house as a system" which is the culprit.

Concrete block structures are 'get wet, storage, and dry out' systems and work well when not fiddled with.

Stucco on frame has its own major problems in that it requires a drainage plane behind the stucco to deal with the water and allow the water to drain out, and that does not mean paper backed metal lath or one layer of felt/WRB, it means two layers, one which serves as a bond breaker and the other the drainage plane (the paper of paper backed metal lath is the bond breaker, NOT the drainage plane).

Add stucco to a concrete block house and it does nothing to stop water intrusion, what it does do is to add mass to the wall and make the storage part of the system capable of storing more moisture.

A concrete block house which is intended to be stuccoed will have the most horrible masonry job imaginable, because 'it is going to be stuccoed and no one will be able to see the masonry work', while a masonry house which is intended to not be stuccoed and just be painted, you will find straight, true, plumb masonry with FULLY MORTARED and TOOLED JOINTS ... and that is the key ... FULLY MORTARED in which the mortar is as required - full face shell thickness MINIMUM ... TOOLED JOINTS in which the mortar is compressed into the mortar joint once the mortar is "thumb print hard".

Slapping a little mortar down, setting the block, slapping a bit of mortar between the two blocks - THAT does not make a masonry wall strong nor weather resistant. Look at a masonry wall during construction, you KNOW there will be problems when you can stand inside and look through the mortar joints and see daylight coming through.

Wront info Jerry , I concrete block wall that is solid block 8x8x16 or hollow with filled cells would be a mass storage system. Depending on the block (cinder or concrte or filled) would determine the quality ofthe mass storage wall. Cinder very porus and not a good system. But this system of solid block does not exist for many buildings. Most systems are hollow block. Some are filled. few are solid block. Hollow block is a barrier system. The block will allow moistue entry unless block filler and a good paint is applied. Stucco will help a block wall barrier system and increase the ability of the wall to repell moisture. The Motar joint is a non isssue in stopping moisture. On a brick wall veneer wall with a 4" joint (tooled and mixed and cured correctly) moistue will pass thru the joint within 20 min with a wind driven rain. Elastomeric paint is a good choice to stop moisture intrusion on block wall and block wall covered with stucco. A big issue with block homes is pressure when force air heating is used, and the dew point falling within the cavity.
This is even more of issue since many walls are comprimised and moistue in in the cavity making dew point easy to reach.

While a poor motar joint wil effect strength and and the bigger issue is that block requires less deflection than a framed building and older block building did not have current structral steel requirments

Originally Posted by Nick Ostrowski

Nearly all concrete block foundation walls I see have some level of moisture penetration. The blocks are moderately porous and not watertite by themselves from my experience.

What type of issues are going on in Chicago Dan? Is it something out of the norm or extreme?

Thanks for all the responses. These are single family homes and larger (6 unit or more) apartment condos. We don't see CMU foundations in the city; the moisture issues are all above grade. Builders here are going as high as 3 full floors with single wythe concrete block exterior walls. These are usually 'split face' or 'rock face' block with bookoo surface area and so porous you can blow into the cores from the outer face. Between the porosity and the missing or poorly installed flashing the result is wet insulation, drywall, and framing. Anyone else seeing this?

Thanks again.

Dan

Originally Posted by Stacey Van Houtan

Wront info Jerry , I concrete block wall that is solid block 8x8x16 or hollow with filled cells would be a mass storage system.

Stacey,

Wrong again.

A concrete block wall IS a storage system.

YOU, for whatever reasons you have, possibly not allowing for new thoughts and concepts (meaning new to you, old and proven methods to others), added the word "mass" to what I said. I did not refer to "mass" storage walls.

Concrete block homes, with only paint on their exterior surfaces, with properly tooled joints, have, for decades, provided water resisting structures for use as exterior walls of homes without leakage through them (except at windows, doors, and other penetrations when not flashed properly).

Originally Posted by Dan Cullen

These are usually 'split face' or 'rock face' block with bookoo surface area and so porous you can blow into the cores from the outer face.

Split face block is known to be not a good water resisting surface, and it is unusual ("rare" is a better word to use) to find a split face block wall which has been painted, meaning the concrete block itself has been left exposed with NO protection whatsoever.

First Jerry go to this site and read some information on block wall systems.
http://www.masonrysystems.org/information/wall-systems-profiles/single-wythe-reinforced-concrete-block/


Then we can have a proper discussion.

I do did use the word mass. This is due to your describing a single wythe block wall as a get wet and then dry out type of system. This type of masonay system, if solid, is designed to be wet and then dry out, it is also a mass thermal storage system. The mass of the masonary allows the system both thermal storage and moisture storage.

It has long been considered that a single wythe masonary wall is a barrier system.

The masonary industry (form what i can tell) does not make a difference between what are really two type of barrier systems. The first a double wythe brick or solid block or stone providing 8" or more of masonary. (this is a get wet, store and dry out system)
The second a single hollow core block wythe with a coating of some type. This system is designed to stop the water at the outter surface and not allow moistue into the masonay units or motar.


The second system is where we typicaly find moisture intrusion prolems.

I will never be to old to learn new ideas and concepts. And more important i can listen to a logical arguement and change my mind. As I have said "show me"
SVH in KCMO

Back to the original question , Dan I would assume that the block are hollow. This is a poor choice in you climate. I would bet the major moisture intrusion areas are: the lack of pan flashings and caulk joints at windows and doors, missing or bad deck flashing, bad parapet flashing, missing or bad Kickouts, bad Chimney flashing , And due the type of block the entire wall.
I would also bet that due to your degree days, that the dew point is reached within the block cavity causing issue on some walls.

We do not have may buildings of this type in KC, and ony some isssues on the what we have. It is not a chronic problem that I am aware of.

Originally Posted by Stacey Van Houtan

I do did use the word mass. This is due to your describing a single wythe block wall as a get wet and then dry out type of system. This type of masonay system, if solid,

Correct ... YOU did use the word "mass" ... *I* did not.

And *I* am not referring to a "solid" masonry or fully grouted masonry construction.

A hollow masonry wall is a get wet and dry out system, which is WHY it does NOT require a WRB over it.

Jerry,

Despite our past opinion differences I would like to invite you to call me the next time you are in Chicago. The concrete block buildings here will absolutely allow moisture intrusion into the interior wall assemblies (insulation, drywall, framing) even if the mortar joints are perfect. The biggest problem we find is poorly detailed or missing masonry wall flashings.

The walls I am referring to are nearly 40' tall and 75' deep. That's a lot of surface area when you consider the 'hard sponge' that split-face concrete block is. Perfect mortar joints won't stop the huge volumes of water that enter the block from running down the open block cores and being drawn into the wall when it hits the window/door lintels, truss pockets, and, eventually the top of the foundation wall.

Plugger paint will certainly help but there can still be penetration via missing coping flashing, wind driven rain forcing it's way into the unflashed or poorly flashed lintel space, etc.

Single wythe CMU construction requires a PERFECT wall in regard to mortar details (thanks JP), flashing installation, and CMU sealing/painting.

Getting back to the original reason for my post. IF ANYONE ELSE IN ANY OTHER CITY/AREA OF THE COUNTRY IS HAVING THE SAME TYPE OF ISSUES WITH CMU CONSTRUCTION IN RESIDENTIAL BUILDINGS COULD YOU PLEASE FORWARD THAT INFORMATION TO ME OR POST IT HERE. OF SPECIAL INTEREST WOULD BE ANY CODE CHANGES THAT OCCURRED AS A RESULT OF THESE ISSUES BEING BROUGHT TO LIGHT.

Sorry for the caps but it's hard to keep folks on track here sometimes. Thanks for any help anyone may be able to provide.

Dan

Hi Stacey,

Thanks for your thoughtful and informed reply. Yes, you are right on track. Your descriptions are exactly what we're seeing here.

Dan