Loft conversion with velux windows and 12" steel support beams... Can i put dormer?

neas

Hi all,

I'm looking at a house with 2 velux windows currently installed.

It has all the correct building regs signed off etc. Its a little small really so would love to replace a velux window with a medium sized dormer window.

On some youtube videos they install a steel beam under the ridge and tie in the dormer to this. I believe the loft extension doesn't have one of these in the ridge.

It does have two 12" steel joists Girders running from each gable end wall to support the floor (supposedly this is overspecced) and the roof presumably (to remove the W trusses).

Does anyone know if the velux window can simply be removed and a dormer put in its place i.e. bolster the frame and support around the window without installing a ridge joist?

Obviously it would be easy to upgrade to a dormer if it just required a bit of carpentry/structural engineer work.

But if it required installed a ridge joist then it would be almost the same cost as doing it all from scratch. The seller informs me this is possible without a new ridge joist as the two 12 inch joists running from gable to gable are well overspecced. I've seen them and they are H type.

Also if it was possible as the extension was done 5 years ago I'm unsure if we could 'upgrade' to a dormer or would it change other elements of the loft conversion that had been previously accepted?

Probably too many questions but hey ho

Yorkie1

Don't know the answer to your particular questions, but have you investigated the Planning Permission side of things? Sometimes a dormer requires PP where a velux didn't.

neas

Dormer shouldnt need PP as its facing rear of property and isnt higher than ridge. Also other people have around neighbourhood so am comfortable with PP more over just technical side of job

System

it depends on the existing roof structure, could be possible but really the only person that can tell you is a structural engineer on inspection of the roof

teneighty

Only a structural engineer can answer your query as already said but as the previous conversion was only 5 years ago the original structural engineer who specified the floor beams should still have their file.

For a modest fee, £100 or so I would have thought they could give you a feasibilty proposal. Although the 12" steel beams in the floor do sound rather oversized I suspect you will still need a ridge beam for a dormer extension but not for a traditional dormer window.