Saturday, 26 January 2013

Put a lid on things

Dear Joe,

I have an addition on my house that was built about fifty years ago.  Because of the location of the windows on the second floor of the house, it was built with a flat roof.  Every spring I go up there and have to fix a leak or two that has erupted over the winter.  I want to be finished with this constant maintenance headache. What options do I have in fixing this issue?  Thanks for your advice.  Love your writings.



Great question Denis,

This is an issue that I have dealt with a few times on behalf of my clients So I am pretty familiar with the possible solutions. 

Let’s start with some background, shall we?  Like you say flat roofs are built for a few different reasons.  Cost efficiency is not one of them so then what are they?  Well considerations that may have been made when it was built could have been aesthetics.  Maybe in order to maintain a lower profile they opted to keep the addition as low as possible.  Or perhaps, like you say, there may have been possible interference with windows on the adjoining wall of the house.  Or , if they did the work themselves, constructing a flat roof was probably less labour intensive at the time then building proper rafters.  At this time efficiency wasn’t an issue nor was future maintenance likely an issue.  So there you have it. Now, what to do about it…

Well, before you build you will have to take into account all the specific site considerations for your house.  What height do you have to the bottom of the windows?    Which side(s) will you be able to shed water from?  What shape will the roof be?  How much overhang will you be able to afford without compromising property lines?  How many penetrations will the new roof have for chimneys, vent stacks, exhaust fans, etc?

So constructing your new slope roof is pretty simple.  All of your trusses can be pre-engineered and are much more cost effective than building them yourself.  Figuring out your slope will be the most complicated part. If you have windows to contend with then they will dictate the slope you can achieve.  Try to get as much slope you can this will aid in shedding water and snow and leaves and prolong the life of the roofing material.  Your building permit will tell you that you must have a minimum of a 2/12 pitch in order to install traditional roof covering such as shingles or tin.  Less than that you will have to have a torched down roofing installed by a professional which will essentially defeat the purpose of doing this work in the first place since that’s what you have now presumably.  So long story short, if you cannot achieve at least 2/12 pitch on your new roof, it’s not going to be a cost effective venture. So unless you are engineering in a significant increase in attic insulation it may not be worth your while. 

So if you’re familiar with construction this isn’t a huge job.  But some guidance by a professional contractor would be a great idea to prevent any pitfalls or oversights as well as navigating the gauntlet of the building permit and inspection process.

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