Thread: Oregon beam span

looking at your shots you are asking a lot 150x70 is undersize to carry the weight of the roof let alone the window weight as well with a veranda hanging of it .
Using the tables for mgp10 pine 240x45 will carry a roof load width of 2.4(half your roof span ) and span 4 mtr not allowing for the window weight you would have to allow that in your calcs as well.regards
BarryTreleaven

I am not a structural engineer. Barry seems to know something about this kind of stuff and he is urging caution. All I can add is a couple of beginner's questions. (1) Is it really only 150mm deep, the pictures make it look deeper than that? (2) I also wonder about the cross beam of the roof itself. It looks like only one beam running across connecting the two eaves. This has to hold the eaves of the roof together to stop them splaying apart. Are they bolted at each end, or does that look like a skew nail? If the roof is allowed to spread it could play havoc with that glass.

There are ways to reinforce it. I had a beam 8 metres long with a centre support and wanted the support gone. An engineer supplied specs to my design and it works. I attached plates each end of the beam and a short vertical post in the centre that dropped about 200mm down. I attached a steel rod at the outer ends and it ran under the centre post. When the rod was tightened at the end plates we actually got the beam to deflect upwards and had to back off the tension. That was all done in steel but it would be practical to do it in timber if you absolutely had to. In your case if you made the brackets in stainless it would look good and be a practical solution. It wouldn't be cheap though. Bear in mind I am only suggesting an outline of an idea, it effectively halves your span but you need and engineer to do the calcs as the span might still be too long for that beam, even when halved. A laminated beam under that would be worth looking at, box it in and it would not look too bad either.

It is considerably under-specced IMO. Mini's suggestion using tensioned steel would work - but you cannot simply replace the steel in such a design with timber! Easiest solution would be to cut off the housed nose part short studs above the beam so you can bolt/screw a new beam adjacent to the existing oregon one - 245-250 x 45-50 would do it - the depth is the primary load carrying factor here.

Another easy option would be to simply add a length of steel angle for the whole span and bolted/ screwed to the existing beam - of course the timber look goes then say 90mm x45mm x 10mm (at 4m that will be heavy!) or a steel U-channel under the existing beam supported by brackets on the ends again 90x90x10 over that span.

I just noticed that one end is also not directly on a post, but part way along on another beam, which also looks light-on to me so my next comment is even more apt:

Really this needs some solid engineering calculations after an on-site inspection to determine the actual loads of roof etc, add the relevant safety factor, and taking account of the winds loads at your site. Structural timbers are not to be guessed at IMO! The consequential of failure are too great - and if is catastrophic failure as is more common with timber then not worth the risk.t safety factor, and taking account of the winds loads at your site. Structural timbers are not to be guessed at IMO!

Originally Posted by Bloss

Really this needs some solid engineering calculations after an on-site inspection to determine the actual loads of roof etc, add the relevant safety factor, and taking account of the winds loads at your site. Structural timbers are not to be guessed at IMO! The consequential of failure are too great - and if is catastrophic failure as is more common with timber then not worth the risk.t safety factor, and taking account of the winds loads at your site. Structural timbers are not to be guessed at IMO!

Penny wise, pound foolish, apt but true when dealing with this sort of stuff. Engineering can also work the other way, that is saving you money by not overspeccing materials. You don't want or need the hassle if this structure fails and all the problems that will ensue from that.

BTW driver75 - you might find a visit to the sister forum and a few searches on 'spans' etc is worth your while on this sort of query - http://www.renovateforum.com