Let’s clear up the confusion about nominal wood sizes

In short, the nominal measurements of the timber are the original measurements when the timber is first cut or sawn from the tree trunk or log before the wood is dressed or is finished. Confusion creeps in when some specify timber nominal sizes while others use finished sizing.

This might not sound like a big deal, but it has a detrimental effect on production and wastage and ultimately costs more.

To make life easier for our customers, at Intrim, all our standard timber dimensions are finished sizes. We are always happy for our customers to order using nominal sizing, but we need that to be specified in the order.

What is nominal sizing?

The reasons why the nominal dimensions of timber are larger than the actual dimensions involve historical practices in the industry.

The nominal number indicates the size the wood was originally cut to. Before it’s sold it is dried causing it to shrink, and then planed to make it smooth. This means the actual size is now different to the nominal measure.

How to use nominal wood dimensions when ordering

If you order your timber trims using nominal sizing, you’ll get something smaller than the size you specified. This is fine if you’re aware of the difference, but it can lead to loads of confusion.

That’s why it’s important to know when plans are drawn up and timber mouldings are specified, whether your dimensions are nominal or finished.

For example, we receive many orders for 100 mm skirting boards, but that’s not a standard size; 90 mm is the standard skirting board size. If you’ve specified a 100 mm finished size (not nominal), then we’ll need to take a deeper skirting board and cut it down to 100 mm, which will cost you more and lead to wastage. If you order a 100 mm nominal size, the finished product will actually be about 94 mm. That might not be an issue for some, but many customers won’t accept anything but the specified size of 100 mm.

How to specify correct sizing for timber trims

At Intrim, we are happy for our customers to order using nominal sizing, but it needs to be specified in the order. Otherwise we’ll assume it’s the finished size for your order and prepare it accordingly. Of course, if we’re in doubt, we’ll call you, but getting it right up front saves you time and eliminates potential errors.

The easiest way to save time and money is to specify the standard finished sizes on our website and then place your order to match those dimensions. That way, you’ll get our standard product, saving money and waste.

Common skirting and architrave measurements

Nominal Size

• 50×25
• 100×25
• 150×25
• 200×25
• 250×25

Finished Size

• 42×18
• 90×18
• 135×18
• 185×18
• 230×18