Resources for Historic Homeowners

John Leeke's Historic HomeWorks™ Question & Answer Column

#10 Insulation Retrofit

"Last year, we bought a 1850's vintage house in Maine with no insulation. After paying our oil company too much we want to add some insulation. The plaster on the inside appears to be in good shape and the clapboards on the outside are in good shape. Despite post and beam walls, the wall cavities appear to be only 2 to 3 inches thick. We'd prefer to have the installation done from the inside, which I gather isn't quite "standard" but I've never seen a "plug job" in clapboards that isn't obvious from 100' away." -- East Boothbay, ME.

If the stud spaces within your walls is only 2" you may have "back plastering" which is a lath and plaster sealing within the stud space. Ordinary insulation contractors may not recognize this complication and may install the insulation so that condensation occurs within the wall causing moisture damage.

Before doing any insulating at all be sure to do everything you can to limit air infiltration. Tighten up the exterior weather envelope by repairing woodwork and caulking open joints between woodwork elements. Add storm windows (interior or exterior) and refurbish the existing windows if they contribute to the historic character of the house instead of replacing them with plastic windows. In a 140 year old house this is bound to give you the greatest "bang for the buck."

Then insulate the ceilings above heated spaces. This should only be done if the attic spaces above can be effectively ventilated to prevent moisture buildup. Painting the ceilings with a vapor retardant primer can help prevent moisture migrating through the ceilings, but the ventilation is a necessity.

One of my recent clients in Belgrade Lakes, Maine just had extensive ice damming and moisture damage due to a poorly designed insulation project. She had to remove most of the insulation, take off all the roofing, and reinstall it along with an effective ventilation scheme. It is worth getting the details right in the first place.

Last consider insulating the side walls. Insulation in the side walls of an older house can trap moisture within the wall during the winter causing superficial damage (exterior peeling paint) as well as significant structural damage (fungal decay). The source of the moisture is usually within the house due to a damp cellar and the moisture generated from showers, cooking, etc. This situation is frequently compounded by adding vinyl siding which traps even more moisture within the wall. In my experience over the past 25 years about half of the pre-1940 house with insulation and vinyl siding have excessive moisture within the walls, and about 10-15% have developed at least some superficial or more serious structural damage.

Window Weather Stripping

Some time since 1924 when our house was built, one of the owners tried to fix the counter weight ropes in some windows. They left out the zinc guide track which is really necessary to keep the wind out when the window is pulled down. This is the usual zinc metal track with a protruding guide rail folded out to accept the groove cut in the window sides. It is trimmed at the foot to sit over the zinc strip tacked across the bottom. The bottom piece is still in place; I just need side pieces.

Check with Blaine Window Hardware, 17319 Blaine Dr., Hagerstown, MD 21740, 301 797-6500, 800 678-1919, They have an extensive supply of older window parts and can fabricate practically anything. Also, Accurate Metal Weatherstripping Co. Inc., 725 S. Futon Ave., Mt. Vernon, NY 10550-, 914 668-6042, may have your type of weatherstripping in stock. Be prepared to send samples for an exact match. If you cannot find an exact match you may end up replacing the weatherstripping with a similar type from these same sources.

Brick Wall Expose

I understand you're the man to talk to! My wife and I are buying a home in historic Fells Point of Baltimore, and we would like to expose some brick on the interior walls. Do you have any ideas or procedures? -- Kevin A. Perkins

First determine if an exposed brick wall is really what you want. Many historic masonry buildings were not constructed with the intent of leaving the interior brick walls exposed. They were left rather rough and unfinished because the builders knew they would be covered up with finished plaster and woodwork. It became a trend in the mid-20th century to expose brick walls because it cost less that restoring the seriously deteriorating plaster and woodwork that originally covered the brick. Many brick walls were exposed, looked too ugly, and had to be covered back up at great expense. The trend of exposing bricks became a "style" of historic building renovation. It is still sometimes done even when the finish plaster and woodwork is in good condition or could be restored or preserved, sometimes at lower cost.

Also you may want to consider heating cost and comfort issues. Removing the finish plaster and woodwork from an exterior wall will increase heating costs and may make the living space less comfortable due to drafts and radiational cooling.

If you still want to expose the brick begin by investigating the character of the bricks. Look through openings that may already be in the wall such as those made for heating and electrical fixtures. You may have to make some openings by cutting through plaster in small areas (perhaps 2"x3" or 6"x6") or carefully removing woodwork. If you find the brick surfaces do not look good in these areas it will be much easier to repair this minor investigation damage than if you just started ripping out large sections of the finish walls. Also determine the construction of the walls and consider how you will run electrical line to the space and how windows and doors will be finished off as they meet the bricks.


John Leeke is a preservation consultant who helps homeowners, contractors and architects understand and maintain their historic buildings. You can contact him at 26 Higgins St., Portland, Maine, 04103; or by E-mail:; or log onto his website at:

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