Ask An Expert

Question

I am a draftsman and commonly draw decks and verandahs for clients, mainly in Victoria. Commonly I have always specified F7 treated pine timber but have been asked a few times if I can replace the F7 with an MGP10 replacement. Looking at different information sets I cant really see information clearly going on way or another. Commonly it notes that MGP10 will work for an F5 and MGP12 for an F8 timber but nothing for F7. My questions then would be, if we are looking to use an MGP10 for deck joists and or bearers would this have the same structural integrity as an F7? Would it last as long (given it would be H3 treated)? Would this be recommended by Wood Solutions who have a lot more experience in this?
 

Woodsolutions Answer +

F-grades and MGP grades don't correspond. For example, F7 grade has a slightly higher bending strength than MGP10 but lower stiffness. To be superior to F7 in all properties it would be necessary to go to MGP12. But MGP12 is way stronger than F7 in strength and stiffness. Also it's possible that for bearers and joists, stiffness may be the determining property rather than strength, meaning that resistance to deflection might govern the design. In that case MGP10 would be able to span further than F7. The easy way to resolve all this is to simply consult the span tables for bearers and joists and see what size is needed in F7 for a particular span. It might turn out to be a larger size, or a smaller size, or the same size as for MGP10. Regarding how long the timber will last, the stress grade is not relevant - F7 properly treated to AS 1604 would have the same expected service life as MGP10 treated to AS 1604. 

MGP grades

Answered on 27-01-2021
Please note that our answer is based on the best advice available at the time. If the National Construction Code, Australian Standards or local requirements have been subsequently amended, our answer may no longer be correct in all details. For more information, please read our disclaimer.

Question

I would like to build a skillion roof using single beams (not trusses) it would be clad with corrugated iron. What size/grade timber would I need to span a 4 metre length? The shed's width will be 6 metres.

Woodsolutions Answer +

We don't generally provide design data for specific projects because of the possibility of not fully understanding all details of the proposed structure. Our preference is to refer inquirers to the span tables and design software available on our website here: https://www.woodsolutions.com.au/articles/span-tables-and-software. Since yours is a simple structure we can tell you that MGP10 grade pine could span 4.0 m, spaced at 1200 mm centres, supporting a corrugated iron roof (no ceiling) in a size of 140 x 45 in a non-cyclonic area, wind classification N1/N2. The roofing material could weigh up to 10kg/m2, which would cover common steel roofing materials. Other combinations of materials can be assessed using the design tools referred to above.

Skillion roof

Answered on 15-01-2021
Please note that our answer is based on the best advice available at the time. If the National Construction Code, Australian Standards or local requirements have been subsequently amended, our answer may no longer be correct in all details. For more information, please read our disclaimer.

Question

Skillion shed end wall 4m high other end 2.4m high rafters at 600crs N3 wind rating metal roof. What size studs?

Woodsolutions Answer +

As well as the details provided, a designer would need to know the span of the rafters. That's what determines the load on the stud walls that support the rafters. It's called the Roof Load Width. In the case of a skillion roof the Roof Load Width is half the span of the rafters + eaves overhang, since each wall carries half the weight of the roof. We have software that will help you to work out the size of the studs. It can be downloaded from our website here: https://www.woodsolutions.com.au/articles/span-tables-and-software. Alternatively, your timber supplier may be able to advise on the required stud size.

Skillion roof

Answered on 17-12-2020
Please note that our answer is based on the best advice available at the time. If the National Construction Code, Australian Standards or local requirements have been subsequently amended, our answer may no longer be correct in all details. For more information, please read our disclaimer.

Sign up or Login to continue reading the answer.

Displaying 0/0

Show me 10 /20 /30

Haven't found what you're looking for?

If you have not found the answer to your question in the Search results, please  send us an email for a prompt response.

EMAIL YOUR QUESTION

Are you looking for a supplier?

Social Media Feeds