Altering a roof to add a dormer window

[sotal]

Hi, I hope this is in the right place.

We are looking at adding a dormer window and I'd appreciate some advice before I get quotes (partly to know if what we want is possible)

Our master bedroom is above the garage. The roof above is short on the front and then long on the back of the house going down to ground level at the back.

Our bedroom is approx 4m x 4m sitting above the front of the garage which is approx 4m x 7m.

We have a loft space above the back of the garage which is accessed from a door in the back wall of the bedroom.

The floor joists seem to continue exactly the same as they are for the main bedroom all the way to the back of the garage so should be perfectly fine to be used as a proper floor. I would like to create a dormer window in this space to give a 2m x 2m ensuite.

Measuring up it all seems to fit.

My biggest concern which I'd like to ask about before I speak to builders about quotes is that there is a big beam running across. It looks very structural at about 1 foot high. I can see 2 of them. One is near floor level and approx 2m into the space from the bedroom - so that one should be fine to be left alone. The one that concerns me is against the bedroom wall and is approx 1.6m high. They both span all the way across the 4m from one side to the other.

I basically want 2m cut out of the middle which would obviously make a massive alteration to the structural capabilities of that timber.

Is this a problem that anyone has come across before?
What would be the way round this?

The obvious thoughts to me are that you would have a vertical strut underneath it to support it - however I don't think the joists would be intended to support the roof as well and it wouldn't be possible to go straight down to the ground as it would put two columns in the middle of the garage!

I presume there is another one a bit further up the slope which is insignificant as it is above head height. And then there will be the ridge itself at the top.

Hopefully that all makes sense - if you need me to sketch something up please say.

I guess in reality I want to know if it is a deal breaker and if not, then what would be the right way to do it so I can present that to the builders.

Thanks

 

[freddiemercurystwin]

Prolly put a new structural beam (steel) running across (at floor level) under the one you want to chop and then build a structural stud partition up on top of that beam to support the one you are chopping a chunk out of. If I understand your dubious description correctly ......

If you want to get serious quotes then you should (at the very least) get some structural calc's/sketches done, they will demonstrate that you a serious preposition to the builders and not just , the details would also give the builders something to quote from and Building Control would require engineers calcs anyway. Though really you ought to employ a technician who will detail the lot and organize your structural calcs too. Then the builders will know what to price and to build rather than sticking a finger in the air.

 

[sotal]

Thanks for the reply, it sounds like you understand it correctly.

I was wondering if a steel at floor level would be the way forward but it certainly adds to the complexity of the project and therefore the cost. It seems though from your reply it isn't necessarily a deal breaker. The builder I used last time had his own bloke for the proper drawings and calculations so I'll probably ask him for a quote.

 

[freddiemercurystwin]

If you've found a good builder you're half way there already!