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RE: Shrinkage of flowable fill against a stone wall

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What’s causing the deterioration?  Perhaps getting water on the site under control and then pointing the masonry will solve the problem.  If the cause of the deterioration is not controlled, you may not be certain that you’ve solved the problem with the fill while access blocked by the fill will hamper an attempt to try something else.


The deterioration on stone masonry mortar joints is conventionally repaired by pointing.  The best reference for pointing is PRESERVATIONS BRIEFS:2 "Repointing Mortar Joints in Historic Masonry Buildings" by Robert C Mack and John P. Speweik, available from .  You may be able to find a local mason who is familiar with the pointing process.  Typically, old masonry building need to be repointed every 40 or 50 years.


Water is the principal cause of deterioration of stone masonry.  Look for poor rain water control, site slopes that deliver water to the building instead of taking it away, irrigated planters next to the building, leaking plumbing – take steps to keep water away from the stone work and, with reasonable attentive maintenance, the stone masonry should last a long time.  The Romans understood moisture control and some of their stone buildings still stand.


Nels Roselund, SE


From: Jim Wilson [mailto:wilsonengineers(--nospam--at)]
Sent: Tuesday, February 05, 2008 2:11 PM
To: seaint(--nospam--at)
Subject: Shrinkage of flowable fill against a stone wall


I am looking to fill a crawl space between stone foundation walls with flowable fill.  But I'm concerned about potential shrinkage of the flowable fill and pulling in on deteriorating stone walls.  One of the goals is to secure the walls at the inside and protect them from further deerioration.


Options we have considered at the stone are:

1. place an 8" concrete wall/curb on the inside of the stone to protect it and bind the cobbles together. Then fill the area between with flow fill.

2. drape a plastic sheet on the stone wall to prevent bonding.  This would also prevent the fill from filling all of the gaps in the stone.  Not ideal.  The

3. Fill holes in the stone with conrete patch and then fill with flow fill.

4. Just fill as is and not worry about the flow fill affecting the wall.


The fill will be about 40'x80', 12"-18" deep.  The foundations support triple wythe brick walls about 24' tall supporting the roof of a church.  The outsides of the walls are several feet below ground.


Am I overreacting about consequences?  Or is there a potential for damage at the interface between old and new? The 8" concrete curb would be a plus, especially if it is reinforced.  But is the extra cost necessary?


I appreciate any insite into flow fill curing behavior and opinions on our detail options.


Jim Wilson, PE

Stroudsburg, PA