It is best to order a DeckProtect that is slightly larger than the outside footprint of the fire pit legs. In the example in this photo, the DeckProtect™ is larger than it needs to be. We have enough sizes that you should be able to choose one that is very close to the right size. If not, you can contact us to see about getting a custom size. DeckProtect™ is built to be strong enough to support the weight of the fire pit even with the extra weight of logs. The legs may cause a little indentation of the basalt board, but not enough to worry about.
Please send us an email if you have any questions about sizing: