When does Wood Stop Changing With the Seasons?

It never does stop.  In your humid season, it expands.  In your dry season, it shrinks.  I might mention, some wood tends to expand and contract more than others.  I try to avoid particle board, chip board, and other similar engineered wood products, as they seem to expand and contract more than others.  Never used Homosoate (a pressed paper product), so I assume it does too.  Plywoods and firs (1 x 4s, 2 x 4's, etc.) seem to be more stable, so I prefer them.

As a long time N-scaler along with some HO scale, I discovered that the best time to lay track was towards the end of the dry season, when the wood was shrunk down about as small as it was going to get.  That helps eliminate track buckling.  Buckling occurs when you lay track with tight joints at the rail, then there is no room for the track to contract.  The rail of course, isn't subject to expansion or contraction based on the humidity.  Hence, it does the only thing it can do to make room on the shrinking wood - it buckles.

Unless you live in an area with fairly constant humidity levels (i.e., the desert Southwest for one), the best thing you can do is build your layout in a HVAC controlled environment.  Heated and air conditioned.  Even with heating and air conditioning, it is not always possible to maintain perfect humidity levels year round.  But it sure helps to minimize the wide swings you may get between dry and moist air in non-conditioned air.

Hope this helps. 

I am going to guess when the humidity kind of stabilizes for the season.   For us northernors that is probably sometime in May for the summer and probably October or early november for the winter.     I know it varies a lot day to day, but in summer is much higher and winter much lower generally.    the wood does react I don't think on a daily basis but over a wieek or more. 

Another thought is when you run your furnace or not.    When you are in the season to run the furnace regularly, it makes your basement usually very low humidity.    When you turn the furnace off for the season, the basement tends to get damp and humid.   

It never stops.  I prefer to lay track in the dead of Winter, when the house is as dry as it is going to get.  When the wood expands in Summer, the worst that happens is some rail gaps get wider.

If track is laid in Summer when the wood has absorbed moisture in the air, the rails will get pressure when the wood shrinks.  Gaps that you cut to form insulated blocks can close and in extreme cases the rails can kink.

The wood you use will have a huge effect on any expansion and contraction.  I'm hoping my choice of birch multi-ply cabinet grade plywood will be more stable than most choices.  11 plies should resist dimensional changes much better than lesser grades of wood.

My experience is the same as Mixed Freight with one caveat.   Some lumber is more susceptible to this than others.   In my current home 10 years old, the bathroom wall pulls away from the vanity countertop every winter and then returns and closes the 1/8 ++ inch gap every year.  This has been going on every year for a decade...  It doesn't happen to any of the walls in the kitchen thank goodness, so there's something about the framing in that bathroom wall that's different.   

One recommendation is to stay away from 2 x 4's in model RR benchwork construction.  There have been numerous books published discussing L-Girder and joist benchwork construction (Lynn Wescott is the author), and he strongly discourages use of commercial 2 x 4's....  I believe they are just a lower grade of lumber that is subject to twisting/warping which is why they are only used for rough framing homes.  

I also tend to purchase higher quality plywood with more ply's (layers), and avoid the cheapest sheet materials for layout work, it just isn't worth the savings and resulting hassle later. 

My personal opinion is that the degree of "movement",  growing, shrinking, twisting being worse in certain pieces is "internal stresses" in the lumber due to the straightness, and orientation of the grain to the finished sides. 

I use a lot of mahogany in historic window restoration, and I cut it into thin strips  3/8 x 7/8 for "parting beads".   What I have learned over 10 years is pick lumber with really straight grain, because when I don't the parts twist immediately after cutting them on a table saw.....  For the past 8 years, I always clamp them back together after cutting so they don't move, (twist & warp) before I have a chance to install them in the grooves they go into to form the window tracks.....   I suppose this is closely related to why "quarter sawn" wood sells at a premium, as it's cut so the grain is perpendicular to the wide face and it's known to be far more stable over time.... Sorry for the long explanation.

I don't have a heated basement, but it's well insulated... I do run a dehumidifier in the summer months to lower the humidity levels....  I do it mostly to prevent preserve the trains, and because I can't stand that damp smell, but I am sure it helps to keep the wood products from changing the moisture content as the humidity rises.   

I wouldn’t worry about plywood.  It is pretty stable stuff.  Cheap plywood may warp a bit unless you have benchwork spaced close enough to stiffen it, but it's not going to grow and shrink from seasonal changes.  I also wouldn’t worry about 2X4s if you are using them for benchwork.  If you are installing track directly on dimensional lumber, I would seal it with polyurethane or alkyd based paint to help keep it stable.

Wood shrinks crosswise to the grain.

It does not appreciably shrink lengthwise. That is how its used in timber supports like 2 x 4's in framing or piles to support a pier or trestle.

S. Islander

S. Islander posted:

Wood shrinks crosswise to the grain.

It does not appreciably shrink lengthwise. That is how its used in timber supports like 2 x 4's in framing or piles to support a pier or trestle.

Au contraire!  I have to say that's certainly not universally true!  

In my previous house, the office above the three car garage was supported using large fir posts.  I had problems for years with the posts shrinking in the winter and expanding in the summer and cracking the drywall and knocking the door frames out of plumb!  I finally bit the bullet and bought a bunch steel of 3" jack poles.  Once I had those in place and adjusted properly, I removed the fir beams, the problem was no more.  I fixed the walls, and never had a crack up there again, and no more door issues!

It makes sense there are expansions and contractions at different times. I think it applies more to newer cut wood, though. On my house framing (been here 35 years), there has never been any noticeable change in the pine wood that was used for the framing. This includes in the attic, which is subject to wide variations in temperature and humidity levels. I've notice that the pine seems to harden over the years; it's almost like oak at this point, it seems. After cured, perhaps the pores close, and the wood becomes harder and much less susceptable to change.

The speed in which a tree grows has a direct relationship to expansion and contraction. Most soft woods are now farmed using fertilizers which increase the speed of growth. The faster a tree grows the larger the growth rings.  Hardwoods and old growth trees have tighter growth rings which minimize the movement.  Maximum movement is with the grain and minimum across the grain. There is a huge difference in plywood, pine being the worst.  More plies equals more stability. I choose not to use composite sheeting because of the high formaldehyde content and most model railroads are in confined spaces. I like cabinet grade birch plywood for my railroad decking.  For joists the  best case scenario is to rip 3/4” birch plywood to 5 inches and then glue and screw a 1”x1” rip of poplar to the top. You can then screw your decking to the poplar rips. Poplar joists work well also because poplar has very fine grain and is a fairly stable hardwood. 

I've never had this problem with my basement layout here on LI, NY.  I pull over a gallon of water out every day with my dehumidifier in summer months, and the basement is very dry in the winter months.

Assuming that we are not talking green wood here, and you are having problems, I'd try a dehumidifier.  If you are still having problems seal your wood on all sides with shellac after cutting it. This will keep swelling and shrinking to a minimum.

Select grade dimensional lumber is typically of higher quality, straighter grain, with few knots. It's kiln dried to a lower moisture content too.
Cabinet grade plywoods like GRJ mentioned will be more stable over time too. I also agree that girder style construction is superior.

If you go with 2x4's look for douglas fir, tends to move less.

Don't buy lumber off the racks at Home Depot or Lowes.

No one has mentioned it but steel framing systems, or C joists,  would eliminate the movement of the base framing. I'm not talking about typical metal studs, Heavier gauge systems are available that would provide the structural stability, but require a bit more effort to work with.

As for the layout room, the better you can maintain the humidity and temperature, the less the wood will move season to season.

Real long runs (40' +/- )  of narrow round the wall bench work will result in some movement action at lift outs.  a friend has an 70' run which really opens up seasonally.  

Ameritech panels are extremely  stable.  They state a .0004" expansion when submerged in water.  Extremely heavy due to high concentration of binding glue.

Working with code .157" solid  NS  flex track,  I leave a .017" floating gap at each joint.  I choose not to solder joints.  My curves are all formed with rollers so there is no need to solder curved track to hold it curved.  All the rails hold a strict firm radius sitting loose.

So much can be gleened from wood flooring specs.  Solid planking can not be installed below grade, engineered wood flooring (read plywood based) can be installed below grade. 

Imagine a plank of wood flooring as a compressed flattened bundle of cord fibers.  When moisture is added it will swell in width considerably but have negligible affect in overall length.  That is why we allow much more room for width expansion than length expansion during installation.

When it petrifies.

Simon

RSJB18 posted: 

Don't buy lumber off the racks at Home Depot or Lowes. 

Lots of things the big box hardware stores carry are of lesser quality. Their wood frequently has a lot of water in it and isn't straight, among other problems. A painter that just did some exterior work on our house said some of Home Depot's (and similar) paints are inexpensive, but don't cover well, so multiple coats are necessary, which ends up being just as expensive as higher quality, better covering paint. Much of their hardware, such as screws, are of lesser quality, too. They break easily, the heads strip easily. The pros buy their screws and nails from other sources. They also buy their lumber from regular lumber yard suppliers. Bathroom/kitchen fixtures may also be of a lessor quality. Producers make several lines of the same style product. The big box sellers may sell the less expensive product, but they're cheaper because they use plastic valve parts, for example. Specialty fixture stores sell the product line made with metal valve parts.

My home, built in 1979 is quite steady. The extremes in northwest Iowa go from -25F to 105F in the dead of summer. I build my 2 rail layout simply. Prime grade 2x4s, prime 1x4s, and 2" 4'x8' sheets of styrofoam, the pink or blue color. I have no problem with expansion/contraction. If you use Home Depots top exterior paint it is highly rated as is their interior Bear brand. I repainted my house about 8 years ago with NO problems. They also sell prime grade screws, look for them. 

Dick

I agree about the low quality of big box store items.  They are my last resort.  I bought 2x4's from the local lumber company - they were not particularly expensive, but straight and overall good quality.  My layout is in a dry basement in piedmont North Carolina.  It is cool enough that air conditioning is never needed, but the humidity can get up to 70% without de-humidification.  I run a dehumidifier set at 50 to 55%.  The humidity will drop to around 35% in the winter.  My entrance bridge is the only place I notice expansion and contraction.  I sanded it to fit in the middle of the summer, and all works well the rest of the year.  Three rail O gauge and standard gauge are large enough that the contraction of the bridge length is insignificant.  My track is glued to carpet padding which is glued to the layout, so it can move a bit it necessary.

Solid wood will continue to expand / contract depending on the season. This is why door panels are made to be somewhat loose while being captured in their frames--so that they can change dimension without changing the overall size of the door or destroying the frame.

initial shrinkage from green to ambiant is dramatic , but after the water in the cells dissipates, changes of around only 5% can be anticipated.  That is across the grain ONLY . wood does not change size with the grain --well, OK, it does--maybe 1/32" or 1/16th in about 8 feet, so it's negligible.

All quality wood things are built with this characteristic in mind.  Avoid stacking or edge to edge when dimensional stability is needed .

Much of the lumber we buy is dried.  The grading stamps will tell you  S-GRN  means over 20% moisture or 'green'. S-DRY means under 19% , or kiln dried to some degree. Furniture and cabinet hardwood is generally  drier, say 10%

Having built a lot of wood cars, & I know most all of you know this, but I have some early nice models ruined because I failed to either seal or control scribed sheeting on boxcar like models.  The damp months {Summer) come and expand , and then the dry comes and contracts, and when it does, it breaks along the scribed lines. If you do not back up such large areas of solid wood by gluing plywood to the back , or allow them to float or seal them thoroughly, this will happen to you  and there is no good way of fixing them .

Kind Regards,

J J Davies  (close to 50 years full time in cabinet shops)      

In addendum, more to the point, unless you have laid track across long areas across the grain of solid wood,  I would not worry about it . you will just have to deal with any problems that occur.  I have seen rail gaps that were blamed on layout framing that were in fact, the whole building moving due to unstable soil conditions. 

In problem areas , like very long track runs, install switch point like slip joints.  draw bridge gaps can be controlled using PC board ties soldered to the rails. this will anchor the rails where it counts and move the problem elsewhere --some place hopefully where it does not matter.  many times I drive brass nails before laying track , and solder the rails down, as in switches near the points where you can't spike on one side.    

J J 

I used construction grade redwood for my framing and Oriented Strand Board (OSB) for the deck.  Both are extremely stable and resist deflection and warping.  BTW, I agree stay away from the big box stores if you want quality lumber.

Speaking as a woodworker who has built furniture for over 30 years...

For solid wood, any project needs to be designed so that it will accommodate seasonal movement across the grain forever.  Proper sealing of the wood and good humidity control will reduce the movement, but it will never be eliminated completely.  Dimensional changes along the length of the grain are very small, and are virtually non-existent once the moisture content of the wood has reached equilibrium with the surroundings.

Plywood will not expand or contract over the length and width.  The thickness can swell if humidity is out of control.

As several previous posts have mentioned, the poor quality of much of today's lumber is an issue, but that's mostly a matter of twisting and bowing.   If using lower-quality boards, let the wood acclimate for a few weeks in the room where it will be used - raised off the floor, and with stickers (1x1 strips) running crossways between each layer of boards.  You'll probably be disappointed at the number which become unusable, but it's better to find out early. 

I generally go to Menards because it's the most convenient for me.  When buying pine for benchwork, I get their "select" boards.  The initial cost is more, but there's less disappointment down the road.  Even when buying the expensive stuff, I inspect each piece for bow, twist, and cup before putting it on the cart.

My home in Raleigh, NC was built in 1923 with southern yellow pine framing. It is hard as a rock but still moves. Doors open in the winter but not in the summer. Keeping a stable temperature and humidity year round helps but doesn’t cure all of it. Mostly you just live with it.

George

Some things to consider for average skilled layout building effort:

As for fasteners, drywall crews were never intended to clamp lumber.  Drywall screws were designed to be used to have a soft clamp stop into the surface of drywall.

When constructing lumber frame work consider using T-25 Star Drive construction screws which were designed for construction. 

Check new lumber purchases with a moisture meter.   Most yards moisture readings  will read in the mid teens.  Acclimate wood until it is in high single digits.  Consider a meter purchase an investment in your expensive layout.

Purchase sheet goods which are stored on flat beds like in real lumber yards.  Always pull from down in the pile.

Pre drilling a pilot hole will yield a better seating.  Pre clamp your wood assemblies, if you can not clamp your wood projects prior to driving the screw home consider drilling a clearance hole.  Use a clearance hole & counter sink in all hard woods.

Behr paint from HD provides very good coverage.  When possible, schedule HD paint purchases for Memorial Day or labor Day when there are healthy rebate promotions.

Also, for base costs or for utility purposes their opps paint is a bargain.  I have use it on rentals and for coating top and bottom of Homosote.  Just mix somewhat similar colors/tones in a 5 gallon bucket for larger purposes.

When you get real comfortable building layouts consider an 18 ga. brad gun with premium polyurathane construction adhesive or Titbond III and a lot of clamps.  Job goes much faster, is very secure, no second guessing.

Select candids:

Note 5 degree Keystone fit in lift out:

Simon Winter posted:

When it petrifies.

Simon

Oh mercy!  I hope you're not counting on this!

Petrification of wood has two basic elements....

Constant exposure to ground water with a high mineral content.

Time: thousands....gazillions....of years.

I'd go to Plan B.....or C....or D....

dkdkrd posted:

Simon Winter posted:

When it petrifies.

Simon

Oh mercy!  I hope you're not counting on this!

Petrification of wood has two basic elements....

Constant exposure to ground water with a high mineral content.

Time: thousands....gazillions....of years.

Well, some O scale modelers are of an age............

The wood in this old home, 1919, is oak.  At the time a 2" X 4" was probably 2" X 4" (today 1.5"X 3.5").  The dimension had changed in 100 years. 

The 21" roof sheeting boards also changed.  Note the gap between boards. 

Balloon  framing, the exterior wall studs are at least 20 ft.  

In high school shop class ( a  long time ago when civics was still taught as well) I was taught that All wood is not the same.  Even the same type of wood. As you know the live part of the tree is the exterior layer. The interior layers are dead; the center layer has been dead the longest. So depending on where the piece you have was sliced from the tree governs its shrink/expand percentage. The closer to the center of the tree the less it will vary.

However when boards are made by cutting the trunk in various ways the board possesses many layers that have aged differently that we call grains. Thus, the board does not shrink or expand consistently throughout its cut length.  If you look at the end of the board you can see how many layers your board was made from. The fewer the layers, showing your board was made from less layers and the less the board will be subject to variable size change. 

Also when attaching a board it is better to nail/screw  toward the center of the tree as shown by the end grain.

How this world would be different if shop and civics were still taught.

breezinup posted:

RSJB18 posted: 

Don't buy lumber off the racks at Home Depot or Lowes. 

Lots of things that the big box hardware stores of lesser quality. Their wood frequently has a lot of water in it and isn't straight, among other problems. A painter that just did some exterior work on our house said some of Home Depot's (and similar) paints are inexpensive, but don't cover well, so multiple coats are necessary, which ends up being just as expensive as higher quality, better covering paint. Much of their hardware, such as screws, are of lesser quality, too. They break easily, the heads strip easily. The pros buy their screws and nails from other sources. They also buy their lumber from regular lumber yard suppliers. Bathroom/kitchen fixtures may also be of a lessor quality. Producers make several lines of the same style product. The big box sellers may sell the less expensive product, but they're cheaper because they use plastic valve parts, for example. Specialty fixture stores sell the product line made with metal valve parts.

Agree totally. While you can use lumber at big box stores, it takes a lot more vigilance with how you use it and where, though of course the big box stores when you need lumber are open 7 days a week, whereas lumber yards are the old 7-4 5 days a week.  Not only is the lumber at big box stores generally not great quality to start with, they also handle it horribly, they leave kiln dried lumber exposed to the elements and it is why so many boards are warped and whatnot. And yes, the quality of the hardware (with some exceptions) is not great, Home Depot carries Spax screws which are better quality for example (they aren't made in China, either US, Germany or Taiwan), a lot of it is just plain junk IMO..and the windows and doors you see from name brand firms are made for HD, and are not as well made (contractor who did my house used Anderson windows from HD, and let me tell you they aren't the same). 

In terms of lumber expansion/contraction, it depends on the quality of the lumber, and also where you have it.  If where the lumber is is not environmentally controlled, then swings in temp and humidity is going to cause it to expand/contract a lot more than one kept climate controlled (not to mention being better on the people who use the layout. I agree that the kiln dried lumber you get at a lumber yard is better than the stuff at home depot and the like, and honestly the difference in cost, least based on my local place, is not bad at all. 

AlanRail posted:

 

How this world would be different if shop and civics were still taught.

Amen, amen, and amen!

And a dose of basic economics would be helpful, too.

But, we digress.....(pun intended)

KD

When comparing layout construction to house based material and methods,  realize, after spending 42 years in residential construction I can safely say:

A sobering consideration, generally speaking is, every aspect of your home is built by the lowest bidder. 

Even in high  end homes, unless the item is personally chosen or line item detailed AND INSPECTED BEFORE INSTALLATION, watch out! 

I have caught hardwood being installed with 1/3 of the fasteners required, corner beading with 4 nails,  no glue under drywall,  dry DVW pvc connections,  no fire stop,  skipped shingle nails,  the list goes on......

The poorest example frequently is in any condo construction.

Deception is common.  There are excellent contractors with high integrity but you must be aware.

There seems to be some very well informed wood workers on board here who deserve listening to.

Hi All,

Tom is right, "There seems to be some very well informed wood workers on board here who deserve listening to."

And thanks to them and all who responded.

Ed