Foundations of the Past: Raised Floors in Old Claremont

Most of the older housing stock in Claremont sits on a raised foundation, and most owners have never been under it.

That is understandable. It is dark, it is tight, and there are spiders. It is also where a startling share of an old house's problems live, quietly, for years before they surface as a sloping hallway or a door that will not latch.

If you own one of these houses, or you are about to buy one, the crawl space is the highest value hour you will ever spend.

What a raised foundation actually is

Instead of the floor sitting on a slab poured on the ground, the floor structure is held above the soil on a perimeter foundation and interior supports, with an air gap underneath.

The vocabulary is worth knowing because you will hear it in inspection reports:

• Perimeter foundation. The wall around the edge that carries the exterior walls.
• Cripple wall. The short framed wall that sometimes sits between the foundation and the floor framing, common where a house sits a little higher.
• Mudsill. The horizontal timber bolted, or in older work sometimes NOT bolted, to the top of the foundation.
• Girders and posts. The interior supports carrying the middle of the floor, often on individual pads.
• Joists and subfloor. The floor structure itself, spanning between supports.

Understand those six terms and you can read most of what an inspector will tell you.

The advantages people forget

Raised foundations get discussed as a liability. They are also genuinely useful.

Everything is accessible. Plumbing runs, electrical, ducting and repairs can all happen under the floor rather than through a slab, which is exactly why retrofitting systems into these houses is far less brutal than doing it in a slab home. That accessibility is the reason the piece on getting modern systems into old walls keeps pointing downward.

The floor is also more forgiving underfoot, and a wood floor over a ventilated crawl behaves differently from wood laid over concrete.

What goes wrong down there

Five things, in roughly the order they matter.

Water. Always first. Poor drainage, downspouts discharging at the foundation, a graded yard that sends the winter rain toward the house rather than away from it. Standing water or persistently damp soil under a house is the root cause of most of what follows.

Rot and pests. Wet wood plus wood destroying organisms. Look at the mudsill, the base of posts, and the joist ends where they meet the perimeter. Damage concentrates at the contact points.

Settlement and movement. Cracked or spalling foundation material, posts that have shifted off their pads, shimming that somebody added in 1978 and nobody revisited. Symptoms upstairs are sloping floors, sticking doors, cracks that reopen after you patch them.

Connection weakness. Older construction was not always tied together the way current practice ties it. Whether a particular house would benefit from foundation bolting or cripple wall bracing is an engineering question about that building, and it belongs to a structural engineer or a qualified retrofit contractor rather than to a general opinion.

Accumulated amateur work. Decades of previous owners solving problems with whatever was in the garage. Posts on stacked bricks. Joists notched for a pipe until almost nothing is left. A ductwork run held up with wire.

The maintenance that prevents most of it

Boring, cheap, and enormously effective.

• Keep gutters working and get downspouts discharging well away from the house.
• Grade the soil so water moves away from the perimeter.
• Keep foundation vents clear rather than blocked by landscaping or stored junk.
• Keep earth to wood contact at zero. Soil piled against siding is an invitation.
• Keep the crawl space clear of stored lumber and cardboard, which is pest habitat.
• Look, or have somebody look, once a year and after any big storm season.

Most catastrophic foundation work I have seen on old houses traces back to a decade of water going the wrong way, which is a downspout problem that grew up.

Buying a house on a raised foundation

Insist on someone actually entering the crawl space. Not a flashlight from the access hatch. If access is genuinely blocked, that itself is information, and it should be resolved before you remove contingencies rather than after.

Bring in a structural engineer if the general inspection raises anything about movement, connections, or previous repair work. An engineer's report costs a fraction of the work it might save you from, or might tell you to do properly.

The broader inspection strategy for these houses is laid out in what old Claremont houses hide, and the foundation is the section of it people are most tempted to skip.

Where historic review intersects

Structural work under the floor is usually invisible from the street, which is often the easiest category in any review process. What can attract attention is anything that changes the exterior: a new access opening in a visible elevation, changes to foundation vents, or work that raises or alters how the building meets the ground.

Whether any review applies to a specific parcel is a question for the City of Claremont, and permits for structural work are their own matter regardless of historic status. Ask early. Structural work is expensive enough without a stop work order in the middle of it.

One hazard note: opening up older construction can disturb LEAD PAINT and ASBESTOS containing materials, both governed by federal and state rules. Testing and handling belong to licensed professionals.

The takeaway

The crawl space is not a scary place. It is the diagnostic panel for the entire house, and it will tell you the truth about how the building has been treated long before the living room does.

Go look. Or pay someone to go look. Then fix the drainage, because it is almost always the drainage.

More across the whole subject at the historic homes hub, and the elements worth protecting above the floor are covered in what to preserve in a Claremont classic. Anthony Grynchal has been licensed in California since November 2009.