Half Timbered Mid-Century Mansion

This important Hudson River house was built of timber with stone in fill, often referred to as half timbering.

In this case, the timbers were dressed with finish boards, but no drip cap. For years the water got behind the boards and in the walls, breaking and cracking the walls. This led to many bad repairs with Portland cement, which made it worse.

Poor drainage and repairs with Portland cement led to rotten beams (click to enlarge)

We installed an extensive drainage system around the building and repaired and replaced much of the rotting timber with masonry. We then pointed and repaired all the walls and installed lead coated flashing over every board.

Portland cement had to be completely removed before repointing (click to enlarge)

The old Portland cement had to be removed to dry out the walls and prepare them for lime mortar pointing. Lime mortars have to dry slowly in order for the carbon monoxide (CO) to exchange with carbon dioxide (CO₂), which is how a lime mortar cures. The lime mortar must be kept wet during the curing process. Do do this, we burlapped over the walls and continuously rewetted the burlap for several days as the mortar cured.

Repointed wall with color-matched lime mortar (click to enlarge)

The repointed wall was kept damp with burlap while it cured (click to enlarge)

In this case, the aggregate size and color of the repair mortar was matched to the original mortar that we found under the Portland cement. We did a wet chemical analysis to determine what the original mortar was to best match it. We were aiming for a very plastic and flexible soft mortar, especially as the walls will always move to some degree due to the half timber nature of the construction. The final color was a very beautiful soft brown. The original sand may have come from the bank of the Hudson River right below the house.

Proper drainage was installed to prevent future water damage (click to enlarge)

Creating a total water barrior that prevents the penetration of water into the walls is the goal of any wall restoration project. This project was filled with various challenges and historical applications of materials over many years that were not done with this in goal in mind. Getting the water away from the foundation and preventing the wicking of water up the walls was essential. We replaced many of the timbers that were rotted out, and in lower sections removed timbers are replaced with masonry to stop the rotting process in the future.

Lead coated copper flashing will direct water in front of and away from the beams (click to enlarge)

The trim boards that existed had been installed on the timbers both horizontally and vertically, with nothing to prevent the water from going behind them and soaking the beams. To remedy this, we installed lead coated copper flashing everywhere, and then pointed it in, creating a drip cap that shed the water out over the wood surfaces, preventing water from getting into the beams. In the end it was all painted and disappeared, making for a nice shadow line and visual effect.

Cured lime mortar (click to enlarge)

This mortar will withstand the movement of the house and flex with it. It will heal itself and withstand the test of time over the next phase of the house. This was a very rewarding project as the house is so special, and rather unusual for the Hudson River Valley.