View Full Version : second story extension and existing roof
24th Aug 2011, 11:51 PM
I'm now planning a second storey extension. The second storey foot print is about half the ground floor. I've been told I'll need to remove all roof tiles to adjust/ modify the roof trusses. I thought they would simple strengthen the trusses to remain remove the tiles from limited part of the existing roof and cut away parts of the trusses as required. Is this not correct? I want to minimise changes to the exisiting roof (and cost) by simply "pop-up" a rectangular extension in the middle. Thoughts?
25th Aug 2011, 09:29 AM
Roof trusses cannot be modified or just cut away as your post suggests. To modify the roof you will need to consult a structrual engineer.
27th Aug 2011, 09:36 AM
If you need to extend your roofline then a truss company would design for you. You will need to tie into existing roof timbers with steel strapping. Saaddle trusses simply sit on your existing rafters, obviously removal of tiles. I wouldnt remove any existing timber. If its a hip end the wall it sits on may need beefing up if you plan to open the space up.
30th Aug 2011, 11:57 PM
Thanks Hoppy. I wasnt going to jump in and modify/ cut the trusses. I just wanted to validate what the draftie told me... That is I would basically have to remove all roof tiles and old trusses and replace with new trusses. I thought the exsiting trusses would somehow be supported and cut away (based on engineering calcs) as required thus minimising work and cost.
Thanks Barney. I suspect I'll have to remove/ cut exising trusses or replace with new ones as extension will include two rooms and bathroom up stairs. I'll consult with truss company.
5th Sep 2011, 08:31 PM
Heres what it would look like, a pic of mine part way through.
14th Sep 2011, 11:25 AM
Thanks for the responses. I've just discovered a new and probably vital piece of information. Old houses (such as mine ) have a "traditional" rafter roof structure" and NOT truss structure. Could this make a difference?
For those not familiar have a look at the link. Roof Trusses vs Traditional Rafters and Roof Framing - Roof Truss Design (http://rooftrussdesign.net/roof-trusses-vs-traditional-rafters-and-roof-framing/)
20th Sep 2011, 10:05 PM
If anyone is interested, spoke to a builder friend. He advised it is possible to modify the 'traditional" rafter style roof, however due to labour costs to modify and re-inforce/support the cut rafters, he believes it is cheaper to pull down the existing roof, build second storey extension, put up new trusses and re-tile. I didnt want to hear that!!
To make matters worse, he told me I will need to remove the hanging beams that hold up the ceiling joist which hold up the ceiling. Hanging beams are large and get in the way of the new second storey floor. However, without support the ceiling joists and ceiling will not stay up. His suggestion was to pull ceiling down given there is almost certain likelihood that it will rain during the time the roof is off and end up severely damaging the plaster ceiling. Another load of bad news!!
21st Sep 2011, 01:07 PM
Afraid to say it's sounding like a pretty standard second floor extension. But in terms of exposure to rain, two friends have done similar, and with a team of a dozen guys both their builders have achieved "from single storey roof demolished to second storey extension framed, roofed and wrapped" within a day.
22nd Sep 2011, 07:54 AM
Wow. That amazes me. I usually work on my own and it's a wonder to me how they all co-ordinate so effectively.
22nd Sep 2011, 08:53 AM
I agree. One of these examples a few doors down, I went to work one morning and when I got home it was 'fully sealed', not lockup but certainly weather resistant.
26th Sep 2011, 11:16 PM
I like the sound of that. Do you think they used pre-fab frame or built on site? How would you pre-fab onto the second floor extension?
26th Sep 2011, 11:31 PM
Its amazing what can be achieved when the production line gets going on site along with good direction. Regarding the hanging beams, the new upper level floor joists should be sized to take the lower level ceiling load ( ceiling joists and all). Whack a few new joists up to replace the hanging beams then joist out the rest of the extension. If the new joists have not been designed to take ceiling load then the ceiling has to come out anyway and a new one screwed to the bottom of the upper floor joists ( on battens)
27th Sep 2011, 12:01 AM
I like the sound of that. Do you think they used pre-fab frame or built on site? How would you pre-fab onto the second floor extension? Yeah, talking to owner confirmed wall frames and roof trusses were pre-fab, and the floor a similar method as described by ringtail.
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