Materials & Techniques


As stated by our mission, our goal is to preserve the historic timber frame structures of New England for future generations.  We have an additional goal of preserving the craft of joinery itself.  Traditional wooden repairs are as much a part of an architectural legacy as the structures themselves.  This tradition is more readily observed throughout Europe than it is here.  At the time when many of the early timbered structures of this young nation would have first required major structural repairs, the industrial revolution was under way and many of the old ways of craftsmanship were left behind in favor of modern efficiency.  We have, on a few occasions, had the good fortune to work on structures that had been restored traditionally a century or more ago.  In these instances, we were able to simply remove the pegs from the repair pieces and re-fabricate the wooden repairs without any additional disturbance to the original structure.  This is an opportunity that we seek to provide to future joiners.

Early on in our restoration careers, when contemplating a repair, we were told to never ‘over-restore’.  This is an idea that has really stuck with us in the development of our preservation and restoration philosophy.  Each individual structure has subtle, and sometimes not so subtle,  details and variations in the techniques and layout of its construction.  It is the nuances of these variations that guides our approach to restoring a structure to be what it was originally intended to be.  Taking liberties in design and technique, no matter how well intended, does not constitute good preservation practice.  Although there may be room for improvement in a structures design, it is more often the case that if a building  is still here to be restored, its design worked well enough.  Changing the details of historic structures jeopardizes our future understanding of history.  Knobb Hill Joinery is always attentive to keeping materials and techniques in kind.  This care extends to the math and layout methods as well as the tool markings associated with each type of layout style.

Why Choose Knobb Hill?

The decision to choose historic preservation and restoration over conventional repair is no small commitment.  Many of our clients have expressed despair in their struggle to find guidance in making informed decisions about the preservation and restoration process.  The terminology of historic preservation is often used casually by contractors and homeowners alike.  Frequently, the term ‘restoration’ is used to describe work that may actually be conventional repair or renovation.  Unfortunately for us, we have to compete in an environment where the nuances of our trade are often enigmatic to homeowners.  As a result, clients often defer to the advice of contractors who may not be well versed in historic architecture or craftsmanship.  Potential stewards of historic structures are often misinformed and choose less expensive conventional repair techniques with the belief that these methods actually constitute proper historic preservation.  There is little in the way of official guidelines or regulation for historic preservation and restoration professionals beyond those set forth by the US Secretary of the Interior.  The SEI standards are broad, subjective and often only given a nod where grant funding is involved.  Numerous contractors have made their careers cutting off tenons and adding metal plates under the guise of historic preservation.  These practices may serve to stabilize a structure in the short term, but often destroy historic details and inevitably shift a greater burden to future generations.  Knobb Hill Joinery has always approached restorative joinery with future generations in mind.  Outlined in this area of the web site are some of the approaches that we feel separate Knobb Hill from our competitors.

Steeple restoration

We have been alarmed at the methods for steeple restoration used by many of our competitors.  Many of the better known restoration companies that work predominantly on steeples prioritize the exterior details of the steeple, but are all too quick to cut corners when it comes to the historic joinery beneath the surface.  Although fabricating a replica of a steeple or repairing one with modern materials may, in some cases, save a few dollars, we feel that this sort of cost cutting comes at the expense of preserving historically significant joinery.  These conventionally framed replicas are merely caricatures of the masterful structures that they replace.  Once the timbers are gone, so is the story of the steeple.

Buying and selling old frames, boards and timbers

Occasionally, Knobb Hill Joinery will unite someone in the region who is interested in acquiring an old frame with someone else who is looking to part with one.  As a general rule, we do not like to support those who profit from removing historic structures from the landscape.  We have found that many of the companies that buy up old frames, boards and timbers do so at the expense of the seller, buyer and the community that has lost a part of its landscape and history.  More often than not, those who buy up these structures know and care little about their history beyond what value the provenance can add to the sale price.  We have heard countless accounts of homeowners being talked into selling a structure for far less than it is worth.  What’s worse is that many of these structures are sold out of state for small fortunes.  We have even heard of one account where a homeowner awoke in the middle of the night to find thieves stealing the boards right off of his barn.  We implore anyone considering the removal, sale or purchase of an historic structure to give due consideration to the ethical implications.  We understand that not everyone is in a position to prioritize or afford the stewardship of historic structures.  When necessary, Knobb Hill Joinery is willing to help broker direct exchanges without commission or compensation.  New England’s historic architecture is a finite resource that we don’t want to see exhausted.


We always favor the use of locally, and sustainably harvested native species of timber and try to match species whenever possible.  Although species such as Douglas fir are popular with modern timber framers from coast to coast, we feel that it is inappropriate to use in New England where it is a non-native species.  We feel that the unnecessary use of non-native species often exploits the communities where the timbers are harvested and unnecessarily wastes petroleum resources in transportation while offering little to support our local economy.

Pressure treated timbers should never be used in the context of historic preservation and restoration.  The factors that lead timbers to rot should be addressed by ensuring proper drainage and airflow.  The use of pressure treated timber is a poor short term solution that will only delay existing site issues for future generation to fix.  In extreme situations where rot resistance is critical, some untreated species, like white oak, are equally as resistant to rot as pressure treated timber.  Most pressure treating methods are highly toxic and volatile.

Laminated and engineered timbers have become more popular over the years, even within the preservation community.  We feel that these materials should be avoided whenever possible and only used in extreme circumstances when all viable timber options have been exhausted.  The introduction of laminated and engineered materials often comes at a cost of the removal of historic joinery and markings.  We have seen major structural failures in these man-made materials and heard countless horror stories from our colleagues about de-lamination.  As of yet, there is no significant evidence to suggest that laminated materials could have the same longevity as natural or joined timber.  We feel that it is irresponsible to experiment with modern materials on irreplaceable historic structures.


In our restoration projects, we always favor the re-use of all intact pegs.  All new pegs are split by hand with a froe and mallet and shaped with a drawknife on a shaving horse.  In the past, we have used sawn or turned pegs purchased from woodshops.

The problem with purchased pegs

We have found a number of problems with purchased pegs. More often than not, the pegs have not been quite the right size and required us to put time into shaving them down.  A bigger problem that we have found has been that the grain in the pegs either rises or runs out of the peg altogether.  By splitting the pegs by hand we are assured that the grain in our pegs is continuous.

What we use

We use oak, ash and locust for our pegstock and avoid species that shrink too much or are particularly attractive to powder post beetles.

Layout and tool-marks

Although layout and other tool markings are not structurally necessary, we feel that they are integral to the historic preservation of a structure.  We always examine timbers for markings and are sure to recreate them on repair pieces.  These markings help to tell the story of a buildings construction.  They can help to indicate the methods used, who the original builder might have been and the date of construction or alteration.

Sills and Foundations

Most of the braced timber frames in New England utilize compression bracing.  The role of the sill system in the function of compression braced frames is often overlooked or taken for granted.  We have had many requests to anchor post feet to dimensional lumber using metal fasteners instead the traditional heavy timbered sill with stub tenon mortises.  Thus far, we have denied them all and lost the occasional client over it.  The integrity of the sill system is critical to the longevity of the frame.  Strong connections to a rigid sill system can help to keep the braces in compression even with moderate shifting of the foundation.  Unevenness in the sills will cause braces to become unshouldered and allow the frame to move.

Most of the structures that we have restored have had either dry laid stone or granite foundations with no supplemental drainage.  Although we have seen many of these foundations shift, heave and sink leading to rot in the sill systems and unevenness in the frames we feel that stone and granite are still the best choice for a foundation.  The majority of the foundations that we have worked on have been from the pre-civil war era and held up remarkably well for their age.  Typically, we excavate the stones, remove loose and loamy soils, add crushed stone and drainage tiles, re-use the original material and re-grade around the structure.  We are often asked about the use of poured foundations and we strongly discourage it.  Although concrete can be sealed, the sealants don’t have much of a lifespan.  Concrete wicks moisture into timbers and accelerates decay.  The lifespan of a concrete foundation is significantly less than that of any given timbered structure.  It makes no sense to us to use a foundation that is sure to fail before the structure that it supports especially when it may actually damage the structure.  We have worked with poured foundations on only a few occasions at the request of homeowners but do not endorse it.  What we do like about stone foundations is that they can be reused or re-stacked for the life of the frame.  When the frame is gone there is no part of a stone foundation that needs to be hauled off to the landfill.

Metal fasteners

There are certain conditions where metal fasteners are appropriate.  In trusses or other joinery that is in tension, metal may be required to supplement wooden joints.  We avoid the use of metal fasteners for repairs whenever possible.  We have seen many poor repairs using metal plates to shore timbers that are rotten or otherwise compromised.  Repairs that use metal are often short term solutions at best that may cause greater damage to the structure in the long run.  Compromised timbers that metal is attached to is often not able to maintain a strong connection under load and will likely fail in the vicinity of the added metal.   Metal hardware often attracts condensation that can accelerate the decay of timbers.  In addition to attracting moisture to the timbers, condensation causes rust.  Rust can expand, with great force, and further weaken connections with the timbers.  This kind of damage in wood that is suitable for a viable wooden repair often leads to the loss of the timber in the vicinity of the metal hardware for future repair efforts.  The shrapnel left behind from metal fasteners causes great damage to a joiner’s edge tools and hinders future preservation efforts.  Metal hardware should only be used as a last resort when it proves to be  the most conservative repair possible.

Glues and Epoxies

Like Metal, glues and epoxies have their place and should only be used when they prove to be the most conservative option for repair.  Once an area of wood has been saturated with epoxy, the affected area is no longer viable for traditional timber repairs.  Glues and epoxies do considerable damage to edge tools.  We have used epoxies to save sections of moldings and other exterior details but have seen very few situations where they would be an appropriate repair for a load bearing timber.  The natural expansion and contraction of wood may loosen glues and epoxies over the years.  These type of repairs may provide a short term solution but do are not proven to have the longevity of traditional wooden repairs.

Rubber membranes and other vapor barriers

The use of modern vapor barriers and rubber membranes has become popular with contractors over the past few decades.  We have seen catastrophic damage caused by these technologies.  Although the function of these membranes is to keep water out, we have seen them trap water.  In some cases this may have been a result of improper installation.  One thing has become clear to us about the use of these technologies, the acceleration of rot is unprecedented.  We have found that structures with good air circulation do much better than those that are sealed up too tight.  Care and caution should be exercised when choosing moisture barriers so that in the event that moisture is able to get in that it can get back out without being wicked up by the timbers.


Spray-foam insulation has become extremely popular for both new homes and old ones too.  Its energy efficiency ratings are better known than some of the health and environmental safety risks.  Spray foam is a petrochemical based substance that often contains benzene and toluene.  Some spray foams are safer than others, but at this point we don’t endorse the use of any of them.  On one job that we did for the Stowe land trust, an uninsulated ceiling in a timbered structure had been coated with spray foam.  The foam concealed water damage from a leaky roof and held moisture that destroyed all of the rafters and a plate.  Once spray foam is applied directly to timbers the patina and historic markings suffer irreversible damage.  The properties of spray foam insulation are inappropriate for use with historic structures.  In another circumstance, a homeowner that we built a frame for chose to insulate with spray-foam.  One of their young children developed health problems that were eventually traced to an incorrect mixture of the spray-foam containing toxic materials not suitable for residential applications.

The first rule of historic preservation is ‘do no harm’.  Modifications or alterations to historic structures should always be done with attentiveness to ensure that they are reversible and to maintain as much of the original integrity and detail as possible for future generations.  One simple technology that we have come to favor for insulating both new and old structures is the Larsen truss.  The basic idea of the Larsen truss is a rigid, lightweight envelope that encases a structure.  The light framing provides an insulation cavity without the thermal gaps found in modern stud framing.  There are numerous, viable insulation types that can be used with this system.  The depth of the insulation cavity can be chosen to accommodate the desired ‘R’ value of a specific insulation material.  The Larsen truss system can be done  cost effectively and helps to support the local economy through the use of local materials and labor.

Although many of the properties of the Larsen truss system may seem similar to those of SIPS (structurally insulated panels) there are some distinct differences.  Many manufacturers of SIPS have modified their formulas to lower the amount of VOCs (volatile organic compounds) and use OSB (oriented strand board) that has ‘only trace amounts of formaldehyde’ in the adhesives.  We feel that there is no room in good building practices for any amount of these toxic substances.  While the amount of volatile chemicals in the finished product may be minimized, the production of these panels is still chemically intensive and unnecessary.  History has shown us other building and insulation products that were thought to be flawless when first brought to market, that turned out not to be so environmentally friendly in the end.  Aside from associated health and ecological concerns, we have our reservations about the structural integrity and longevity of SIPs.   Moisture or water leakage can cause irreversible swelling in OSB, particularly at the edges.  We always try to consider what kind of future maintenance scenarios might arise when choosing materials and techniques.  Although SIPS have been shown to hold up well under ideal conditions, we try to plan for potential neglect.  Since the SIP’s are a unit, the failure of any part of the sip may require the entire panel to be removed.  This would mean disturbing the, often delicate, interior finish details as well as pluming and electric.  The use of a Larsen truss system offers the option of replacing insulation materials in the future without disturbing utilities or interior finishes.

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