What I'm Seeing Now


When Plumbing Holds Up A Foundation

Could PVC be the other white meat, I mean foundation support?

Remember the 100+ year old property with the stone foundation?  Poly-foam had been used in many areas to "repair" mortar gaps in the foundation.  Here's the problem with that.

In Virginia, a stone foundation dates a house before 1915 or so.  Other things come into play.  If you research the history of cement used to build foundations, soft mortars were used.  A "soft mortar" was one that used a primarily lime-based mixture.  It was softer than today's mortars which use Portland cement ingredients. 

The old, soft, lime-based mortars were perfect for stone foundations, especially when the exterior stones are sedimentary.  The exterior portion of the stone foundation in my previous post was sandstone.  It was selected apparently for its pretty beige color.  Granite was used on the interior.  Soft mortars flake from moisture migration, pull away and fall out.  As this was happening on the Manassas house, the homeowner used Poly-foam to repair it.  Not much could be a worse repair.  And modern home center mortar mixes (Portland-cement based) would have been just as bad.

Portland cement was not introduced until about the 1870's, and then only minimally.  It was not popularly used at the primary ingredient in cements until the 1930's.

Portland cement is much harder than the old, soft mortars.  It poses a problem when re-pointing older stone foundations if used on the exterior.  When used for interior re-pointing Portland cement performs quite well.


As the soft mortar begins to fall out, it must be repaired immediately.  If enough falls out stone foundations have a tendency to bulge inward. Portions can collapse.






Like this.

What you see here are interior granite stones which have crumbled. 

Look closely and you can see moisture along the bottom of the foundation.  The floor is concrete and is stained the color of the mud.  This foundation floods regularly and there is a sump pump in the middle of the floor to collect the flooding water as it makes its way inside. 

The sellers reported to me that this flooding is regular.

Do you see the PVC drain line?







It is actually holding up a large section of foundation which has collapsed inward!  Hard to see from this angle, the stone is virtually floating in that position.

The electrical panel box is empty and not used.

The copper drain line is used and vulnerable.

And yes, the insulation is upside down, improperly placed everywhere.

Any bets as to how long this PVC can hold up that collapsed wall?  It is sizable!

Pieces of it have crumbled down, as you saw in the previous photo.

The room above this spot has a different, related  problem which I will show on another post.

When re-pointing that loose mortar on the outside, rather than Poly-foam, a soft, lime-based mortar should have been applied.  This is why the smart, historic homeowner will consult an experienced, historically-cognizant,  professional before effecting any repairs to any aspect of the house!  My guess is that many modern masons would not know which mortar to use for re-pointing.

My recommendation:  Be smart!  You don't know what you don't know.  If you own a historic property, and an issue crops up, do some research (there are MANY websites) and consult people who know what you do not.  In the long run, not only will you be happier, but your house will be too...


Jay Markanich Real Estate Inspections, LLC  

Based in Bristow, serving all of Northern Virginia.

Office (703) 330-6388   Cell (703) 585-7560


Comment balloon 10 commentsJay Markanich • January 14 2010 04:53AM
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