What wood for bookcases

[Nicknoxx]

Hi All

I've asked this in another place but having browsed for longer, it may be better to ask here. I'm planning to make a wall to wall bookcase which will be painted but I'm not sure what wood to use for the construction. Obviously needs to be cost effective but most important is the shelves don't sag. The span of the shelves on the right hand side is 820mm but the span over the doorway is 138mm. It may be possible to put an extra support in the middle of that span if necessary. Any suggestions? (and yes, there is a gurt big RSJ in the middle of the room)

Thanks
Nick

Here's a Sketchup drawing:-

 

[marcros]

do you want the grain to show through, or when painted is it to be pretty neutral.

If the latter, i would use mdf. if you want the grain to show after painting, something like ash would do nicely. somewhere on the forum is a tool to work out section size to prevent sag.

 

[milkman]

sagulator!

Previous poster: Did you mean ash?

OP: did you mean 820mm and 1380mm?

Assuming 18mm mdf fixed shelves and 200mm depth its giving out a sag of 1.276 mm per 305 mm over a span of 820mm. You are aiming for 0.51mm per 305mm so you would need to go for a thicker shelf, use wood, apply an edging strip or narrow the spans.

If you used a rear edging strip that is also fixed to the wall this would improve things!

: ) Marko

 

[marcros]

yep- edited...

 

[Jelly]

If you're painting it, but want grain to show then redwood would be my first choice, it's relatively cheap and plentiful, every builders or timber merchant will carry it... If you have a big timber merchant nearby, and you don't mind doing some planeing yourself the you could go for whitewood carcassing material, to save even more cost; you'd want untreated which isn't universlly available though. Whitewood also has a lower level of movement in service than redwood (or most other things come to it).

I personally wouldn't want to use good (and comparitively expensive) hardwood like ash under paint!

 

[Nicknoxx]

sagulator!

OP: did you mean 820mm and 1380mm?

: ) Marko

Whoops, yes 1380mm.

 

[Steve Maskery]

OK. Make the basic unit out of MRMDF. Make all the shelves as a torsion box. Yes it's a lot of work, but you did say that above all it mustn't sag. Material cost is low, end result is high. Just factor in the time to make the shelves rather than just cutting pine that will look like a hammock in a fortnight!
S

 

[Nicknoxx]

Hmmm, not sure about the torsion box shelves. As you say it's going to be a lot of work (and my time does have some value) but it will also men thicker shelves which would make the whole thing rather too chunky.

If I use 25mm MRMDF for the vertical parts how deep should I make the rebates for the shelves (assume 25mm ash shelf)? I'm thinking about a third of the way so 8mm on each side.

 

[petermillard]

Are the shelves fixed or adjustable? If it were me, I'd make the whole thing out of 25mm MR MDF; hardwood 'D' profile lipping on the shelves adds significant 'anti-sag' but I'd be tempted to make a torsion-box arrangement for the bottom shelf over the doorway with steel box-section bolted behind the leading edge to keep it solid.

Vertical dividers for the shelves above would spread the load, especially if they're staggered. A pelmet or face-frame of the same thickness as the torsion-box shelf all along the horizontal would even things out, and/or make a handy recess for e.g. lighting.

Lots of options, but I wouldn't mess with 'real' wood for something like this, personally.

Re the depth of the housings; my old woodwork teacher would always say that he could support the whole school on 1/8" (3mm) rebate, so anything over that is OTT IMHO.

HTH Pete

 

[Benchwayze]

do you want the grain to show through, or when painted is it to be pretty neutral.

If the latter, i would use mdf. if you want the grain to show after painting, something like ash would do nicely.

Agree. You could use a good quality plywood, but the layers tend to show, whatever you do, unless you lip with solid wood.

I don't like painting hardwood. Not for anyone, although I might 'lime' English oak.

 

[Togalosh]

Hello Nicknoxx,

Just the thought of all that painting (primer, flatten, 1st coat, flatten, 2nd coat... & in all those corners) only to have it on MDF that would very easily chip, dent, scuff & blow would make me go to IKEA & go on a Saturday !

If it was my choice I'd go for Larch as it's cheap, commonly available (but maybe not kiln dried), light, plenty strong enough, easy to work & finish (no horrible fine MDF dust).. & it would perhaps match a ply backing if you chose to show the grain somehow.

IMHO that is

Togs

 

[richarnold]

We are just making some book cases in the workshop at the moment, and we are using our usual choice of wood, which is tulip wood, This is our number one timber for all internal painted work. It's cheap, has hardly any knots, or shakes, and sands, and machines like a dream.

 

[Togalosh]

We are just making some book cases in the workshop at the moment, and we are using our usual choice of wood, which is tulip wood, This is our number one timber for all internal painted work. It's cheap, has hardly any knots, or shakes, and sands, and machines like a dream.

Is this the same as Poplar?

I think it looks great but I thought it too....soft. Does it not bruise & split easily ? I have some but found it failed easily when jointing.

Togs

 

[Steve Maskery]

American Poplar = Tulipwood = Canary Whitewood

Ys it bruises easily, because it is quite soft, but it paints superbly and should not split under normal circumstances. I've used it on a number of projects and never had that problem.
S

 

[Benchwayze]

Are the shelves fixed or adjustable? If it were me, I'd make the whole thing out of 25mm MR MDF; hardwood 'D' profile lipping on the shelves adds significant 'anti-sag' but I'd be tempted to make a torsion-box arrangement for the bottom shelf over the doorway with steel box-section bolted behind the leading edge to keep it solid.

Vertical dividers for the shelves above would spread the load, especially if they're staggered. A pelmet or face-frame of the same thickness as the torsion-box shelf all along the horizontal would even things out, and/or make a handy recess for e.g. lighting.

Lots of options, but I wouldn't mess with 'real' wood for something like this, personally.

Re the depth of the housings; my old woodwork teacher would always say that he could support the whole school on 1/8" (3mm) rebate, so anything over that is OTT IMHO.

HTH Pete

My old woodwork teacher's party trick was to freehand saw 1" oak planks on a table-saw.
I learned after I left school, that he lost a finger and thumb! I don't know the details, but I think I can guess!
(I hasten to add, apart from that, he was fine craftsman.)

 

[Steve Maskery]

+1 for the 3mm housing. You don't need much.
Re torsion boxes - now are you moving the goalposts here?
S