Actual timber sizes vs notional

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mdf

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#207338 19-Dec-2016 21:42

I am trying to complete a project without visiting Bunnings 27 times. I'm building an outdoor cabinet storage thing that will need framing with something reasonably lightweight though ideally treated. I'd prefer something with a roughly square profile. I've seen standard sizes include notional 45x45mm and 45x35mm, but does anyone know what the actual sizes of these are are for when I work up my plans?

richms

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#1692476 19-Dec-2016 21:55

Firstly, go to timberworld or some other independant place, not bunnings for materials.

Secondly, it depends on who milled it to a degree, they are not mm accurate at all, and may change even from the same place on subsiquent orders.

Richard rich.ms

mdf

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#1692477 19-Dec-2016 22:01

Wellington lacks independent timber merchants in any kind of reasonable location (reasonableness judged by proximity to where I live), so unless it's a big enough order to make it worthwhile to travel, I'm stuck with Bunnings. Unless I want to pay more and go to Placemakers.

Actually, I take that back. City Timbers and Mouldings + Finishings are good at what they do, but that doesn't include cheap framing timber.

mattwnz

20164 posts

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#1692539 20-Dec-2016 00:13

There is a tolerance + or minus a certain amount. Generally 50x50 is the roughsawn version of 45x45 dressed. There is probably some timber association which has those listed. But perhaps the best thing to do is get some samples from the merchant. Not a lot of competition these days in this market for consumers.I found Bunnings had the best pricing in the Wellington region last time I was looking for decking timber.

dickytim

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#1692549 20-Dec-2016 06:23

timber also swells with moisture etc. I am building a fence and finding this as I am doing it a bit at a time after work.

I am lucky as I have Wecks/ITM locally and Max Brit sawmills so getting the timber is easy and a lot cheaper.

Bunnings and Mitre10 are about 2 times more expensive :(

Disrespective

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Uber Geek

#1692564 20-Dec-2016 08:25

Timber comes in various nominal sizes. They're Rough Sawn, Band Sawn, Green Gauged and Dressed. All can be called up as Ex. 100 but all will be slightly different final measured sizes.

- Most internal finishing timber is what's called dressed. It's the finest finish, smooth, and ready to paint (mostly). (90mm)
- Green Gauged is what structural framing is. It's going to have radiused corners and some defects so not ready for paint. (94mm)
- Band sawn is a rough surface on the timber which would be ready for stain. (~94mm) But I can't actually be 100% sure here, i'd need to call a timber rep.
- Rough sawn is pretty much straight from the mill saw. It's rough, and really only good for fencing. (100mm with tolerance of -1 to +3mm)

Call sizes are: 40, 50, 75, 100, 125, 150, 200, 225, 250, 300
Gauged are:   37, 47, 69, 94,   119, 144, 194, 219, 244, 294
Dressed are: 35, 45, 65, 90,    115, 140, 180, 205, 230, 280
Dry framing: 35, 45, 70, 90,    120, 140, 170, 190, 240, 290

In your examples 45x45 would be a dressed piece of 50x50, and 45x35 would be a dressed piece of 50x40.

Disrespective

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#1692567 20-Dec-2016 08:32

dickytim:

timber also swells with moisture etc.

If you're buying timber for a fence you could buy wet timber which should be slightly cheaper as it's not been kiln dried, and you should find it has much less movement as it's already fairly high moisture content.

Disrespective

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#1692587 20-Dec-2016 09:15

Oh, @mdf I also just saw that you're doing this for outdoor use. You might want to think about timber treatments so the item doesn't rot over time. H1.2 is for indoor use only, H3.2 is for outdoor, above fground, use. H4 is for outdoor on-ground use. H5 is for use outdoor in ground. You won't find any dressed pine timber that has been treated i'm afraid. You'll need to look at gauged framing timber for that. Or a different species which is less rot prone when outdoors such as Macrocarpa, Cedar, Kwila, Garapa etc. Unfortunately most of these don't come in standard timber sizes as they are used for decking/cladding purposes.

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NotReally

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#1692590 20-Dec-2016 09:23

Using wet (treated H3.2 or higher at above 27%) or dry (kiln dried after treatment to below 20%) timber for a fence, deck, or retaining wall has no effect on subsequent movement. Timber shrinks when the moisture content falls below 25-27% (fibre saturation point) and then swells back to the original size when at 25-27%. Above 25-27% there is no movement. Outdoor timber will swell and contract with the weather, this is what causes surface checking.

The difference is the gap required in palings and decking. Use a smaller gap when the timber is wet as it will shrink, use a larger gap when dry as it will swell. Get it wrong and you will have problems.

Dry dressed finishing timber is usually sold at the actual size (i.e. 45x35) by the lineal metre ($/LM). You don't need to worry about actual vs nominal sizes. Framing timber may be labelled as nominal (100x50) or actual (90x45) but is also usually sold by the lineal metre at timber merchants. Only sawmills use cubic metre rates as a standard price.