Restoration, Renovation, Rehabilitation, Conservation: What Does it All Mean?

When talking about historic architecture we often use terms such as restoration, renovation, conservation or rehabilitation.  However, these terms have very specific meanings when used in particular contexts which can be quite different from how they are commonly understood.  It can be especially confusing when speaking to preservation professionals who use these terms following established definitions.  For instance, we frequently hear people describe "restoring" their 1890s home by remodeling or updating the kitchen and plumbing or installing French doors.  Is this truly a restoration?  Keep reading to find out how a preservation professional uses these terms so we can all be on the same page and avoid confusion.

Restoration: A true restoration is the process of returning a building to its appearance and condition at a specific period in time. This means making a house look exactly like it did at a certain date, including recreating the wallpaper, matching historic paint colors and matching or reproducing fixtures and hardware. True restorations are quite rare and largely limited to house museums like Mt. Vernon or Monticello. Many of the things called restorations really aren't.  The example I gave above of remodeling and updating a kitchen and plumbing is not, in fact, a restoration.

Renovation: If remodeling and updating a kitchen and plumbing is not a restoration, what is it? It is a renovation. Renovation is the process of making something look and function like new.  Replacing period HVAC, plumbing and wiring or adding French doors is a renovation since you are making an historic building work and function like a new building according to today's standards.  Although a renovation can be quite sensitive to the historic nature of a building and preserve as much as possible, it is a different act.  Although there can be some overlap between restoration and renovation, it is good to appreciate the differences.

Rehabilitation:  Rehabilitation means something very similar to renovation, but it is often used in a slightly different context.  Rehabilitation is the process which seeks to preserve the historical portions or features of a building while making the building compatible with a new use.  A good example is rehabilitating a brick, 1870s horseshoe factory to be used as lofts or commercial space.  This term is often used in conjunction with tax credits which encourage the preservation of historic building for income-producing businesses.

Conservation: Conservation is also fairly rare and normally done in house museums.  Conservation is the preservation of particular building features for the future.  In other words, it is the process of arresting decay or decline so that the original workmanship and materials survive as they are now found.  This might mean cleaning and protecting a fresco in a church so that it doesn't continue to be degraded by leaking water or soot.  It is different from restoration because restoration would mean returning the fresco to its appearance when the church was built. However, restoration can be a destructive process because, in order to make the fresco appear new, you would have to alter or destroy some of the original workmanship.  Sometimes the materials and workmanship have such historical value that we simply halt their decay and leave things as they are so that we can appreciate them as examples of historic craftsmanship.

Is your woodwork hungry? Should you feed it?

We all know there is plenty of advice on the internet and that some of it is very good and some of it is poor.  One topic that I encounter frequently as a preservation consultant is the care of historic woodwork and furniture and the apparent need to feed, nourish or moisturize wood.  Unfortunately, most of the information circulating on Facebook and the internet about this is quite incorrect.  Although I may be a voice in the wilderness, here is my attempt to set the record straight.

Your woodwork does not get hungry. It does not get thirsty. It does not need to be fed.  You do not need to give it a drink.  Examples, testimonials and recommendations of people doing so are legion but they are misguided.  Moisture in your woodwork or furniture is a function of the ambient humidity in its environment.  Humid air means wood has a higher moisture content and drier air means wood has a lower moisture content.  It is as simple as that.  What is important is to limit the frequency and amplitude of swings in humidity and temperature because this cycle of expansion, contraction and moisture content will cause wood to swell and contract and can degrade historic finishes or cause cracks and checking.  It is important to moderate these swings to the extent you are able by limiting changes in temperature and humidity levels.

“Feeding” your woodwork or furniture with linseed oil, tung oil or orange oil will not replenish moisture.  After all, how can oil replace water?  If you are thirsty do you grab a bottle of Wesson oil out of the pantry and take a drink?  Of course not, and your woodwork is no different.  Oil doesn’t feed wood either, but it can be quite harmful.

There are two types of oil commonly used on woodwork: Drying oils and non-drying oils.

• Drying oils: These include linseed oil and tung oil. They are called drying oils because the molecules cross link or polymerize when exposed to oxygen.  That is, they harden or form a film.  This is why they are used in varnishes, paints and other finishes.  They are harmful because continued use will saturated the wood and, when they drying oils oxidize over time, they will turn dark or black. This is irreversible.  The real tragedy is that this process can take years or even decades.  People will swear up and down that this is untrue, but this is only because they haven’t been around long enough to witness the entire process.  Ask any furniture conservator what they have seen.  Indeed, many museums have wonderful pieces of furniture that have been ruined because they were repeatedly sopped with linseed oil decades ago and subsequently have turned dark or even black.  The key word to remember here is CONTINUED use.  Although drying oils were used historically to make varnishes, paints or other finishes, it is the continued, repeated and liberal use of drying oils that saturates the wood and can cause damage down the road.
• Non-drying oils: These include orange oil and lemon oil which are often mixed with beeswax. They are called non-drying oils because they do not cross link like linseed oil and remain liquid or semi-liquid.  Although they aren’t harmful like drying oils can be, they don’t nourish or feed wood.  When used on vanished wood they sit on top of the existing varnish and, over time, will form a gummy film after the volatile elements have evaporated.  The gummy film can be quite thin but still will attract dirt and grime and create a mess that can be especially nasty on molding and in corners.  To combat this people will apply more orange or lemon oil to revive it.  This does restore a shine temporarily, but the process continues.  Non-drying oil should never be used on unfinished wood because the oily gunk will penetrate the wood and cannot be removed.

What are we to do to care for woodwork and furniture?  A paste wax polish on a clean surface.  Woodwork should be clean and dry and covered with a paste wax or beeswax polish (with no orange oil!).  There are plenty of good products on the market that work well. I make my own paste wax using an 1850s recipe that I tint to match the color of the woodwork.  This is one case where what they used years ago continues to work today.  A yearly coat of wax is all that is needed to protect your woodwork or furniture.

One more thing to remember.  Never use anything out of an aerosol can since these sprays contain silicates which can saturate the finish and can't be removed.  Natural wax finishes are the way to go.

I know there are people reading this who will strongly object and assert that I am uninformed and completely incorrect.  They will claim they’ve been using products containing linseed oil to condition their woodwork for years with no ill effects.  Well, I have made my case and you are free to do what you wish.  However, if have any doubts and are curious, feel free to Google the American Institute for Conservation of Historic and Artistic Works and see what they say.  Or, keep saturating your woodwork with linseed oil and hope for the best.