Stack It Up

A log home comes to­gether a lit­tle dif­fer­ently than con­ven­tional con­struc­tion. Here’s how.

Log Home Living - - 2018 AN­NUAL BUYER'S GUIDE -

Log homes aren’t just dis­tinc­tive by the way they look, they also stand out for how they’re built. In a con­ven­tional house, the weight is sup­ported ver­ti­cally, but a log home’s struc­tural sup­port comes hor­i­zon­tally, with the load of the house rest­ing al­most en­tirely on its perime­ter log walls. It’s crit­i­cal that they be built to pre­ci­sion. This is known as the join­ery sys­tem.

The load-bear­ing sur­faces are known as the hor­i­zon­tal sur­faces. Th­ese sur­faces form the top and bot­tom of the log pro­file, or its shape as viewed from the end. The sides of logs are known as its vis­i­ble sur­faces and de­fine the look of the logs when stacked.

There are many dif­fer­ent hor­i­zon­tal in­ter­face de­signs to ac­count for the nat­u­ral ten­dency of logs to shrink, swell and twist as they dry (for ex­am­ples, turn to page 32). Wood species re­act dif­fer­ently dur­ing their sea­son­ing process, so pro­duc­ers de­sign a sys­tem that works best for them by tak­ing into ac­count the type of wood they’re us­ing, its mois­ture con­tent and the logs’ size and pro­file. One ap­proach is not su­pe­rior to an­other — much de­pends on your se­lec­tions and per­sonal pref­er­ences.

Be­sides pro­vid­ing struc­tural sta­bil­ity, the hor­i­zon­tal in­ter­face must al­low for a weather-tight seal. Many man­u­fac­tur­ers cut grooves and chan­nels to ac­com­mo­date seal­ing ad­he­sives — usu­ally foam or caulk­ing — and cre­ate an im­pen­e­tra­ble bond.

Other re­fine­ments in the hor­i­zon­tal in­ter­faces are check­ing and dry­ing grooves and drip edges. Be­cause up­ward-fac­ing checks can col­lect mois­ture, the check­ing-dry­ing groove lets air reach the log’s in­ner core so it dries at the same rate as the log sur­face to min­i­mize check­ing.

But that’s just the be­gin­ning. Let’s re­view a few of the build­ing ba­sics that cre­ate a solid, well-built log home.

KEEP IT TO­GETHER

Once the logs are stacked into walls, they need to be se­curely fas­tened to re­main aligned while ac­com­mo­dat­ing dif­fer­en­tial set­tle­ment — the ten­dency of logs in a wall to shrink at dif­fer­ent times, rates and amounts.

As part of their build­ing sys­tem, pro­duc­ers rely on a fas­ten­ing sched­ule, which pre­scribes the lo­ca­tion and fre­quency of each fas­tener. The grade of logs, species, mois­ture con­tent and lo­ca­tion of win­dows and doors all af­fect the type of fas­ten­ers used.

Pro­duc­ers al­most al­ways in­clude fas­ten­ers in their ma­te­rial packages. Your pro­ducer may of­fer more than one fas­tener op­tion or spec­ify us­ing more than one type of fas­tener on the same wall. The types of fas­ten­ers com­monly used in log walls in­clude spikes, screws, drift pins and through-bolts.

Spikes are ba­si­cally huge nails. Va­ri­eties in­clude smooth shank, spi­ral shank and ring shank. For most wood species, the builder must first drill a hole to ac­com­mo­date the spikes, which are driven into the logs with a sledge­ham­mer. A draw­back to this fas­tener is that the logs, par­tic­u­larly if they’re cut with a tongue-and-groove in­ter­face, can be dam­aged if the sledge misses the head of the spike.

Lag screws are pointed bolts avail­able in dif­fer­ent di­am­e­ters up to a half-inch. Again, holes must be drilled in the log to ac­com­mo­date the screws, which are tight­ened with an im­pact wrench. The screws are in­stalled at stag­gered in­ter­vals so one is never on top of the other. The holes need to be coun­ter­sunk, ei­ther by pre-drilling at the pro­ducer’s fa­cil­ity or by the builder on­site.

Through-bolts are threaded rods that are in­stalled in holes drilled ver­ti­cally through­out the en­tire wall sys­tem. In some sys­tems, through-bolts are com­bined with tension springs to aid in the home’s set­tling. Once the en­tire wall is as­sem­bled, the bolts are tight­ened at the foun­da­tion level. The bolts re­quire re-tight­en­ing pe­ri­od­i­cally as the home set­tles. This is some­thing you, as the owner, can do.

Drift pins are of­ten re­quired in ar­eas with high seis­mic ac­tiv­ity. Th­ese pins are typ­i­cally gal­va­nized pipe or re­bar set ver­ti­cally in the wall sys­tem in drilled holes. They’re typ­i­cally placed 4 feet apart and at each side of win­dow and door open­ings, although in earth­quake prone ar­eas, they can be as close as 8 inches apart.

Threaded log home screws of­fer the ben­e­fit of not re­quir­ing pre-drilling. The in­staller drills and coun­ter­sinks the screws in one step. Although smaller in di­am­e­ter than other fas­ten­ers, most threaded screws are heat-treated for equal or greater strength.

Struc­tural ad­he­sives bond wood to wood, so the ad­he­sive bond set­tles nat­u­rally with the wall.

When con­sid­er­ing your op­tions, un­der­stand than no sin­gle fas­tener works best. Re­gard­less of which fas­tener a pro­ducer uses, it will be cal­cu­lated into the de­sign and en­gi­neer­ing of your home.

SEAL IT UP

Once erected and se­cured, a log home needs to be made weather-tight. That’s where sealants come in. Sealants pro­tect your home against air and water in­fil­tra­tion. They are needed in log home con­struc­tion be­cause of the spe­cial na­ture of wood and what hap­pens to it af­ter it is har­vested — namely the way it checks, twists and shrinks as it ad­justs to its new sit­u­a­tion as part of your log home. Com­monly used sealants are caulk­ing, chink­ing, ad­he­sives, foam gas­kets, ex­pand­ing foams and splines.

Depend­ing on the wood’s mois­ture con­tent level, the great­est move­ment in your wall logs will oc­cur dur­ing the first two to four years af­ter con­struc­tion. Any move­ment af­ter that should be min­i­mal. So, a suc­cess­ful sealant sys­tem should ac­com­mo­date a con­sid­er­able amount of move­ment in the first few years, as well as the less dras­tic changes than oc­cur over the life of your home.

Whether they’re crafted by hand or milled by a ma­chine, turn­ing a pile of cut tim­bers into fin­ished log walls re­quires man­power.

Log fas­ten­ers are over­sized nails, screws and bolts de­signed to con­nect logs so that they func­tion as a unit to re­sist stress caused by strong winds, heavy snow and earth tremors. The fas­ten­ers are in­stalled at pre­scribed in­ter­vals to max­i­mize their per­for­mance. Depend­ing on their type, they’re ei­ther driven di­rectly into the wood or in­stalled through pre-drilled holes. Fas­ten­ers and in­struc­tions for their ap­pli­ca­tion are usu­ally in­cluded with log home kits.

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