Ahhhh, the sweet smell of fresh cedar!: The Roof Restoration Begins

Omar and Luis installing the first sections of the new roof. The sheeting above them is used to protect the attic below in the event of rain.

Craftsmen from The Historic Roofing Company have been working diligently since the beginning of the month to replace the well worn wood roofing system on The Hilleary-Magruder House. Installed during the 1980 restoration, and now over 35 years old, the system has held up amazingly well, a testament to quality specifications, materials and installation. With few exceptions the roof has kept bad weather out as intended for even a bit longer than expected.

The roof is composed of what is called a 4-layer wood shingle system. Using 24″ vertical grain western red cedar “Royals,” the roof essentially has a extra layer of protection as opposed to a more typical 3 layer roof of the same material using 18″ perfections. That, in combination with the traditional open roof sheathing has allowed the system to breath and maintain equilibrium far better than a hybrid approach common today in wood roof shingle systems. As this is a restoration project (replace-in-kind) the system will be replaced using the specifications from the 1980 restoration by James T. Wollon, AIA, since it performed so well. During the demolition reconstruction we documented some areas of particular interest and/or concern for evaluation and treatment.

The original spaced sheathing and rafters are white oak. The 1980 restoration  replacements are white pine. Our replacements are poplar. This attic hasn’t seen daylight for 35 years!

The process began with a visual inspection of the roof structure to determine any soft spots in the system which might present a safety concern for the workmen. A few rafters and sheathing areas were flagged as potential areas of concern, mainly where cracks or excessive sagging was observed in the structure and where spotting from rainwater leakage was detected. Close inspection of flashings at walls, dormers and roof penetrations was also performed.

Since the roof is gambreled (it has two pitches on each side with a break in between), the main roof replacement process was broken into four phases: 1&2 tear off the old shingles and replace the top sections of roofing on each side (including flashings around the chimneys), and 3&4 tear off and replace the lower half of each side (including, the 6 dormer roofs, valley, sidewall and sill flashing). A 5th phase of the roofing replacement includes repairing all of the associated trim, and finally the lower porch roofs and trim must be similarly treated.

This work all has to be carefully coordinated with the masons working on the chimneys and the carpenters restoring the dormers so a water tight envelope is maintained during the process and so that the flashing details are correctly completed.

Chimneys are Okay!

After much scrutiny it has been determined by AEON Preservation Consultants (AEON) and Federal Masonry Restoration (FMR) that the chimneys are essentially sound, and only minor repairs are necessary. Our concerns here were that they had been significantly “rocked” during the earthquake in 2011. Several of us were in the basement when we heard, felt and then saw the shock wave travel through the building on that day in August!

Our chimney story begins with photos from the early 20th c the first showing the building in its earliest photographed configuration. In the 1922 image, note that both chimneys are largely intact with corbelled and vaulted tops and appear to be unpainted. The brick on both chimneys is showing some signs of deterioration, as unevenness in the surface is apparent.

 

The next image taken in 1933 shows that the East chimney top has been rebuilt, but without the corbel and the vault is as a result a little smaller as well. By measurement the East chimney is shorter by the height of the corbel, and the quality of the vault is inferior to the original.They both remain unpainted and the deterioration does not appear to have gotten much worse.

The 1970’s images of the building show it in perhaps its worst state. Aside from cheap roll roofing and a lot of roofing tar applied to seal the chimney and dormer flashing areas, the chimneys have now both been stuccoed over. This is most evident as the corbel details on the West chimney have been smoothed out by the thick coating.

 

The “as-built”1980 restoration which we are working from in this project diverged somewhat from that proposed in the architects construction documents. Those drawings show restoration and repair of the existing brick work, but a decision was made to retain and repair the stucco over the brick work. Further, in an unusual detail, the stucco was extended over the chimney flashing as a counter flashing, making it impossible for us to replace the roof without disturbing the stucco at the intersection of the roof and both chimneys. This had already failed as cracks had telegraphed through the stucco at the point where it was no longer attached to the brick and simply floated on top of the flashing attached with a strip of galvanized metal lath.

FMR masons chase cracks in stucco surface on West chimney to reveal structural conditions.

So FMR’s first task was to remove loose stucco and chase cracks that had telegraphed through the stucco, and remove enough material at the base to free up the flashing, and look for signs of catastrophic structural weakness (system discontinuity from the quake and other lateral force events like hurricanes, micro bursts and Durrechos), and systemic weakness (general brick and mortar condition failure) if any.

Much to our surprise (and relief), we found very little of either! Almost all spot checks revealed that other than the changes described above, the masonry was in good, largely original (to 1742 or certainly that era) condition.

 

 

 

 

As with any building this old few areas of concern do have our attention though.

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  Aluminum flashing and stucco counter flashing condition at West chimney all appear to be from the 1980 restoration. flashing tuck location appears to be in original location, very low to roofing.

  The chimney step flashing once revealed was found to be consistently very close to the roof level, less that 3″ in some cases. This was contributing to some mortar deterioration below the flashing and perhaps some of the moisture related blistering of plaster in the 2nd floor chambers as water seeped through the system and found it way out.

• The roof along the front and back of the West chimney was flashed to a dramatically sloping roof condition which appears to have been sagging since early in its life. Further investigation of the structural reasons will be included in another post.

• The middle of the brick vault atop the West chimney was sagging significantly and loose brick work was evident, though a very heavy portland cement parge coat remained intact above the brick. From initial visual inspect there was concern it was a sign that the entire vault was in a near state of collapse.
  

  1980 stucco patch on top of West chimney vault (top), and new flue liner and falling brickwork (bottom).

  But looking at the 1980 restoration drawing and chimney brickwork below the roof line in the attic AEON and FMR determined that there was a clay flue liner repair apparently conducted at that time and the area of weakness was relegated to that repair only as they had to remove a portion of the vault to prepare chimney and slip the replacement clay liner into the the chimney mass.

 

Natural hydralic lime product to be used in filling voids and all masonry surface repairs.

So the good news is that the repairs will require less intensive measures that originally though might be required. FMR will finish chasing the cracks resetting the few bricks in the chimneys where loose, and pointing parging with with a natural hydralic lime in several lifts to ensure the integrity of the repairs and seal the surfaces. The surfaces will then be coated with a breathable masonry coating which will be determined once all repairs are complete.