In this Issue: A Timber-Frame/Modular House Hybrid House
 

Fine Homebuilding Magazine
 

This economical house design features factory-built
 rooms that surround a post-and-beam core

November 1999 No 126
U.S. $ 6.95/Canada $ 7.95

My husband and I like to think of ourselves as as practical people who are not afraid of a challenge. For years we had been dreaming about building a post-and-beam house for our retirement. We had always admired the tradition of timber-frame construction and liked the bright, open spaces in the timber-frame homes we have seen. Lush post-and-beam catalogs whetted out appetites. We also anted a house that was big enough to accommodate visiting children and grandchildren. However, because all the prices we were quoted ran over $ 120 per sq. ft., we had to rethink our plans.

Engineering a compromise


During our research of several companies, we met Kent Natirbov of Techbuilt Custom Homes (Pre-Engineered Housing - 6752 Old McLean Village Drive, McLean, VA; 703-827-8203) a design and supply company.

After we discussed our situation, Kent assured us that we could save money by incorporating a timber-frame center attached to factory manufactured modules. Frankly the concept of prefab housing bothered us. Like many people, I think we confused modular with Mobile. A tour of Kent’s preferred modular subcontractor changed our minds because of the level and degree of quality control was so impressive. Moreover, we could customize any part of the design as long as we didn’t deviate from the width of the module.

Designing in concert with Kent, we planned a total of six modules for the entry, kitchen, powder room, laundry, master bedroom/bath, two upper bedrooms and baths, plus a study. (See Floor Plan) all built around a timber-frame great room.

We decided to use panelized construction for the garage only; we found it it is a faster method, especially when there is a crane already on the site. A long open front porch and a screened back porch would be stick built on site.

Careful planning is the rule

There is no turning back in the modular world. Modules arrive complete; everything from drywall, plumbing and wiring to switch plates, windows and doors installed at the factory. There would be no way to change door openings or sink locations once the plans get to the factory floor.

Due to the width limits on most roads, modules can be put together to make large rooms, but no individual box can be wider than 14 ft.

We also had to consider the placement of doorways and halls that linked the great room to the modules. Because the modules’ door openings are in place when they arrive, the finished floor heights in the timber frame had to match exactly.

To allow for variations, the great room plan called for approximate door measurements; smaller-than-final size openings were cut out of the stress skin panels to provide flexibility in the final matching with the modules.

Electrical planning became very important as well.
Five separate electrical subsystems had to be  carefully planned so that they could be wired into the main electrical panel under the kitchen module with relative ease would be cut and framed later.

The wiring for the great room had to be installed as each stress skin panel was put in place.

Crew scheduling is critical

Unlike houses built by one crew, our house was built by a number of specialized crews - so one of the most important tasks became crew coordination. With help from our construction manager, we undertook the general-contracting job, knowing full well that it would add to the stress but would save money in the long run.

Once the foundation (one crew) was in and the timber-frame erected (another crew) we needed a third crew to set the modules in place.

With the modules set, we would need a fourth crew to integrate the modular and timber-frame sections. It was a rainy fall - if these roof and side wall junctions were not linked together ASAP, rain from the next  storm would leak down to the great room and damage the drywall interior of the stress skin panels.

Last, the roofing crew was scheduled to shingle the post and beam section and to weave all the roofs together

Concrete Block Foundation

Our foundation walls had to be both sturdy to support the weight of the house and wide enough to accommodate the side by side wall plates where timber frame and modules met. To make sure there was ample room, Techbuilt specified 12” wide block.

The entire block foundation was grouted in every cell and reinforced with vertical rebar at 3’ intervals.

Also incorporated were block piers that would support the marriage walls of the master bedroom modules and the carrying beam that would run beneath the great room/master bedroom walls.

Once the foundation was complete, work began on erecting the frame. Aided by computer generated design, the Crew had cut and assembled the frame in their shop, broke it down, and trucked it to the building site.

They reassembled the bents on the ground and hoisted them into position with a crane. Stress skin panels completed the first section of the house. The entire process took six weeks.

The modules stack up fast

Scheduling the exact day for module arrival was com0plicated by weeks of rain. A lead person from the module manufacturer came down to manage the local set up crew. His careful briefing developed good crew coordination.

The next two days were exciting for us after all our months of planning.The plastic wrapping on each module was removed, a huge crane lifted each unit, and the set-up crew guided each into place. The crew pushed to do the job and set the six modules in two and a half days. We kept sneaking inside to see how everything lined up and to check the features that we had ordered but had never seen. After they filled in the gables ends and pulled off interior supports, the crew strapped the modules to the foundation with hurricane ties on 16” centers.

Although the modular and the timberframe sections were freestanding, the crew also tied the sections together on exterior corners, using three galvanized angle brackers per story.

The site-built roof extensions, called overbuilds, were the last link between the post and beam’s exterior and the newly set modules.
 

Trim work unites disparate sections
 

After so much activity, the pace of the finishing work seemed to drag on. But as the garage, porches, and cedar clapboards were added, our house became more horizontal, bleontrastnding into the wooded setting. When painted, the white trim and porch details provided a nice contrast.

Inside, openings between the modules and the great room were finished. Pined window frames and moldings in the great room were stained to match those in the module. We indulged ourselves and bought clear heart pine for the great room floor.

When th 6’ spiral staircase was installed on the newly varnished wood and we could ascend to the balcony above, we knew that the parts of our house had finally knit together as planned.

Once the dust settled, we crunched numbers to see where the money had gone. After factoring in porches, heated basement, and garage, we were surprised by the results.

The modular part of the house cost 12 % less than the timbedr frame - a figure probably due to the kitchen and bathrooms. Tile and hardwood floors, solid surface counters, the geothermal heating system and a 100 ton crane pushed up the modular price. Still, if we had timberframed the entire house, the cost would have been much higher.

By using modular construction, we saved a great deal of time and we were also able to contol cost and quality. We saved money by taking on many of the management tasks ourselves; our sweat equity also included a big chunk of the electrical work and some finish carpentry.

Free-lance writer Libby Schroeder lives in Moorsville, NC with her husband John