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velux window size (cutting rafters)

  • 01-06-2010 10:10am
    #1
    whosedaddy?
    Registered Users Posts: 925 ✭✭✭


    Hi,

    I was talking to a roofer about fitting 2 velux windows and he said he wouldn't recommend cutting more than 1 rafter - would weaken the roof too much. The rafter spacing is 30 something cm, which would limit me to 66cm wide window.

    Any thoughts on that view?
    Should I look for different roofer or is he right?


Comments

  • #2
    ShamFeen
    Registered Users Posts: 229 ✭✭ShamFeen


    I couldn't say for sure as I don't know your roof, but I have seen 2 and even 3 rafters cut for windows. As long as you beef up the structure properly and displace the load properly, i.e double or triple headers all around the window, you should be fine. Try asking a carpenter (preferably a good one!!).


  • #3
    mp22
    Moderators, Business & Finance Moderators, Regional South Moderators Posts: 6,854 Mod ✭✭✭✭mp22


    You would need to double up on the rafters either side of the cut,(hard to do on a finished roof)then as said double headers.Use hanger plates as well.


  • #4
    martin46585
    Closed Accounts Posts: 342 ✭✭martin46585


    the most common velux used is a m04, 780x980 size, these are especially sized to fit between the first and third rafter, cutting out the second, if you follow, meaning only cutting one rafter. (based on 16" centres)
    if you can access the roof from the inside it should be straight forward enough to place an extra rafter along the outside of the first and second rafters, going from load point to load point if possible, (ridge,purlin,wallplate etc)
    just double up your trimmers, to complete the opening.
    hope this helps........................


  • #5
    whosedaddy?
    Registered Users Posts: 925 ✭✭✭whosedaddy?


    Thanks guys. Didn't have a chance to doublecheck in the attic, but I'm pretty certain it's less than 16' center - hence my question.
    A M04 78cm wide window would require two rafters to be cut. House was build in the 50s and access from inside is no problem.

    I was mainly wondering what is best practice..

    Will of course get another roofer / carpenter to give me opinion and price.


  • #6
    tiocimarla
    Closed Accounts Posts: 241 ✭✭tiocimarla


    whosedaddy? wrote: »
    Thanks guys. Didn't have a chance to doublecheck in the attic, but I'm pretty certain it's less than 16' center - hence my question.
    A M04 78cm wide window would require two rafters to be cut. House was build in the 50s and access from inside is no problem.

    I was mainly wondering what is best practice..

    Will of course get another roofer / carpenter to give me opinion and price.
    You can cut two or three rafters if ye like. If your chippy is qualified he will know that depending on a few basic factors, all it is is doubling up and trimming the roof.(trimming, trimmed, trimmer) Its basic roof knowledge for a chippy.
    Only problem is he will have to support the roof while this is done. Post pics of the inside of your attic and the oppisite side and il c can i tell you what will be required.
    Ive worked with dozens of chippys that have been on site for years qualified and never gone near a roof. This may be the case here or maybe he has foreseen a problem in doing so that might run up the cost or even cause instability.


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