Glulam house in Batumi and Georgia: factory kit, assembly and cost

People choose a glulam house when they want timber walls but aren't prepared to wait a year for the house to settle. Glulam is glued together from dry boards called lamellas, and it holds its size better than solid timber. The price for this is a higher cost and strict demands on the design: the house arrives from the factory as a set of numbered parts, and a mistake in the drawings can no longer be put right with a saw on site.

What a house kit consists of

Glulam is turned into a house kit by a machine: it planes the profile, usually a fine multi-tongue “comb”, cuts the notches at the corners, the grooves for the settling frames in the openings and the holes for the dowels. Every piece is marked, the kit comes with an assembly diagram, and the crew builds the walls by the numbers with almost no fitting.

For the walls we usually use 180–200 mm glulam. Floor beams, transoms and rafters are often made of the same glulam: it comes longer and straighter than solid wood and doesn't twist after installation. What comes from the factory and what we buy locally is fixed in the specification before the order.

Designing for the factory: what we decide before ordering

The factory turns the architectural design into shop drawings, breaking each wall down into individual timbers and joints. Our structural engineer checks them against the Georgian seismic building code and the ground on the plot, and at this step the anchoring to the foundations and the wall sections next to large windows often change. We don't take on a calculation that the factory made for its own country without this check.

Before the order goes into production, we settle questions that in a masonry house are usually left for later:

• the size and position of every window and door, including the sill height;
• the electrical routes: if the factory drills cable channels in the timber, the sockets will end up exactly where they were drawn;
• the water and drainage entries, and the extracts from the bathrooms and kitchen;
• the places for heavy items: kitchen units, the water heater, the TV.

Once the factory has started cutting the timber, moving a window means new timber and a new delivery. So you sign off the shop drawings as a separate stage.

Ordering the kit and accepting it on site

We have no production of our own: we order the house kit from a manufacturer for the specific design. Glulam may also be imported, so we name the manufacturer and the country the kit will come from in the estimate. The production time is set by the factory, and we find it out before the contract is signed, to know whether we can get the roof on before the autumn rains. If the kit comes from abroad, delivery and customs clearance are usually handled by the supplier, and we prepare the access, the unloading area and the crane for the lorry's arrival.

On acceptance we count the pieces against the schedule and inspect the packaging. If the wrapping is torn and the timber travelled wet, we record it in the acceptance report. We measure the moisture content, check the ends for delamination along the glue lines and match the markings to the diagram. Which questions about the adhesive to ask the manufacturer in advance we listed when comparing glulam and solid profiled timber. Until assembly the kit is stored under cover, raised off the ground on bearers, and we slit the factory wrapping at the bottom so that condensation doesn't collect under it.

Foundations for a house kit

The timber arrives with machine precision, and the foundations have to be just as precise. If the top of the plinth varies in height or the corners don't match on the diagonals, the first courses sit with gaps, and the error travels up the whole wall. So before the damp-proofing goes down, the site foreman checks the top of the plinth with a level and measures the diagonals, and the readings are attached to the stage certificate.

Most often we pour a cast-in-place slab with a plinth: it gives even support across the whole footprint and also serves as the base of the floor. On a slope it usually ends up as piles with a cast-in-place ground beam, and how the choice between them is made on different ground we described when comparing pile and slab foundations. The anchors for the bottom course are cast into the concrete to the factory's diagram, and the site foreman photographs them before the pour.

Assembly and finishing with no pause for settling

The walls of a kit go up quickly, and after delivery the shell is usually under its roof within a few weeks. Glulam hardly settles. Its thickness does still change slightly with the moisture in the air: it takes up water in summer and gives it up in winter with the heating on. So windows and doors still go into settling frames with a small gap, and the rafters and staircase still get slip joints, although the allowance there is much smaller than for profiled timber.

Finishing starts straight away. Inside, the timber is sanded and coated with oil or lacquer, and the bathrooms are built on a separate frame with moisture-resistant plasterboard, so that the tiles don't depend on the movement of the wood. On the outside we apply a preservative and a wood stain with UV protection.

Long beams and large spans

The lamellas are finger-jointed along their length, so a glulam member isn't limited by the length of a trunk, and it is used for beams that profiled timber can't span: a living room with no supports in the middle, a double-height space, a cantilevered canopy over a terrace. The beam sections, the supports under them and their connections to the walls are calculated by the structural engineer, and the factory cuts the beams from the same drawings as the walls, along with the pockets for the supports.

A long wall has its own limit. If in the design it runs further without cross walls than the calculation allows, it is braced with a short cross wall notched into it or with pairs of posts bolted through the wall, and space for them is built into the shop drawings. Floor-to-ceiling windows work in a similar way: the wider the opening, the less solid timber is left in the wall to hold the house in a tremor. So we agree the width of the glazing with the structural engineer before you sign off the shop drawings.

Glulam house in Georgia: when it is worth it

Glulam costs noticeably more than profiled timber, and we recommend it where the difference buys you time and less upkeep:

• a year-round home you need to move into in the same year the build starts;
• a house to rent out that has to take guests by the coming season, not after a year of settling;
• the owner lives abroad, and there is nobody on site to adjust the doors and screw jacks;
• a house with a glazed gable and large spans; how such a house is built on a masonry lower floor is described on the page about chalets.

If you like exposed beams with glass between them, take a look at half-timbered houses, where glulam works as the frame. Glulam is a poorer fit for a plot where a lorry can't get in and a crane can't stand, and for a tight budget: then a timber house is better built from profiled timber or as a timber frame. An even more factory-made option with wood on the inside, CLT panels, is described on the page about CLT houses.

How much a glulam house costs

The shell of a glulam house costs from 1,980 to 2,400 ₾ per m² of floor area. The price includes the foundations, walls from the factory kit with assembly, floors and the roof. Windows, building services, finishing and the design are priced separately. A turnkey glulam house costs from 3,000 ₾ per m², and finishing starts straight away, with no pause for settling.

Separate items: a glulam wall with materials and installation from 690 ₾ per m² of wall, a foundation slab from 390 ₾ per m² of the house footprint, and thermally broken aluminium windows, installed, from 780 ₾ per m². Profiled timber is cheaper, with a shell from 1,200 ₾ per m², and CLT panels cost more, from 2,220 ₾.

Costs go up with a larger timber section, panoramic glazing, a complex roof and difficult access. They come down with a simple plan with repeating walls and standard-size windows. We send a preliminary estimate from a sketch within 24 hours on business days. The final cost is set on the basis of the design and the factory's shop drawings, after a visit to the plot and once the estimate is agreed.