Alex

Rafter in wrong place!!

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Hi All, 

 

Issue cropped up today when getting ready to slate the last of the roof. When we reached the roof light opening and were measuring up to batton out the openings we realised that the openings are to big for the Keylite Combi flashing supplied. Basically the flashing requires max 100mm between openings. However due to info given to me by Keylite I've allowed for tolerances on each of the openings so middle opening is approx 45mm to wide since it turns out the middle opening doesn't allow for any tolerance with this flashing kit!! I need to move the twin rafters over by this amount. 

 

Options: 

1. Strip roof, gutters, fascia and soffit, cut out trimmers and then add new full length rafter (birds mouths both ends as seated in web of steel ridge beam and wall plate) and then cut out rafter in the way. Add vertical trimmer on far right to maintain spacing

2. Come up with a way to cut out part of twin rafter (XXXX in picture) and add vertical trimmers (white boxes in picture) 

 

I'm posting as my structural engineer was busy on another job and now it's the weekend so have no idea what I should do. The roofers were going to be finishing off this last section tomorrow (sat) which would mean that the roof is finished and they're due to start a new job on Monday! So may be a couple of weeks or more before they're available to help finish off... 

 

The spec by engineer is for twin rafters between windows. If I cut and trim as per the picture it would mean that there is only 1 continuous rafter but with the amount of structure around it to my untrained view it should be ok! 9_9

 

I'm a mixture of annoyed that I was given duff info months ago and stressed as I can't afford any delays at the moment (mainly due to needing to get to weathertight stagepayment!)

I'm resigned to having to chase engineer on Monday but hoping I might get some ideas / reassurance before then that I don't have to go the extreme of stripping the roof to move a rafter 45mm!!! 

 

Rafters.thumb.JPG.bdab9cd35d5fa924c74c5c90fe053266.JPG

 

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I'm afraid I can't help but I can see your issue, my only suggestion to do it without stripping the roof would be to beef up the left and right doubles enough so you could trim right through and do what you like with the ones in the middle. but I don't know how off the top of my head,

 

possibly quiz @albert about his in situ laminating,

 

 

or pester @StructuralEngineer for some wisdom

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9 hours ago, Construction Channel said:

[...]

possibly quiz @albert about his in situ laminating,

[...]

or pester @StructuralEngineer for some wisdom

 

Took the words out of my mouth, Ed . As in  '' Ask Albert '  Maybe a PM to him would help.....

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I would look at this from a different angle.

 

The issue appears to be the window flashings and the minimum overlap in a situation of adjacent windows meaning you need to put the windows closer together.

 

I would instead be looking at what you can do to make the flashings work with what you have, first suggestion being a roll of lead down the doubled up rafters before you put the flashings on.

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On 4/6/2018 at 21:41, Alex said:

with the amount of structure around it to my untrained view it should be ok!

 

If you take out the section in red you will need to reinstate a full length rafter at the location in blue. Also you'll need to fix the trimmers at the locations where you have now cut the supporting rafter (in green).

 

Keylite have an engineering department -- have you given them a call? They might be able to advise on an easier solution: https://www.keyliteroofwindows.com/help-centre/after-sales-support/

 

5acb1fc562aaf_keyliteopening.thumb.jpg.d419f982e4bb6dd30c770197f9be3bc8.jpg

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Hi i would suggest that all the openings will be incorrect so adding a spacer as shown to all openings and making a cover strip / flashing to fit would be my first solution. You cant really cut the double or sistered rafter. cutting out hangers and removing square twists will leave a mess and most likely a hole in the membrane.  You could use the laminated system but this is a large span with a decent load so it would need to be calculate and approved by your SE.  They may be happy for you to shorten your trimmers by 50 mm and sister a rafter up butt jointed glued and bolted  but would be better to use 2 x  25mm ply or graded timber substantially  lapped and  jointed. I would say a good roofer will sort it externally with just packing from inside if the veluxes can be spaced equally.

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the other opting is to trim down your flashing kits  or use a thinner but better product where youve not got the desired allowance from key lite. I would find a solution  other than to strip and refelt batten ideally.

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After messing around for a few days looking at options it basically came down to a cost and time issue. I didn't want to spend more money as over budget in a number of places! (:$) and putting cost implications to one side all of the options were going to take time and therefore delays.

 

So I took a pragmatic approach to this.... ( see pics) 

 

The slating is now done and the roof looks great, just got to find the time to get the fascias and soffits finished now. 

 

20180410_132200a.jpg

20180411_172923.jpg

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