Flat Kitchen Roof - Turn to pitched

[meso100]

I currently have a flat kitchen roof (extension to the house).

Its not that big.

The flat roof has, well, had its day and has sunk in so many places.

I have had a rough quote to turn this into a pitched roof with Marley tiles and new fascias and guttering of circa £750.

I doubt it will ever cost me much less than this whichever roofer I use, but my question is, does the old felt need removing and then the roof beneath covered with plywood? Or should I just clean up the flat roof and pitche tiles over it?

I am just worried about any underlying rot which may have occurred.

Lastly, would I need to insulate the kitchen roof at all?

Thanks guys

 

[DAZB]

You will probably find it would be best to remove the old flat roof completely because the new rafters will need somewhere to fix to and access to the deck joists and wallplate is needed really. You can also check for any rot or decay this way and I would also take the opportunity of installing a good filling of insulation in while you are able to.

 

[noseall]

it is possible to leave the existing joists in place, fit a wall plate to the top of these joists and then pitch the roof from here. this is good enough to counter spread.

you may need to fit restraint straps to the new wall plate.

you will need to fit insulation between the joists and across them so removal of the existing deck may be necessary.

don't forget venting.

£750 sounds remarkably inexpensive! what size is the building?

 

[noseall]

oops!

 

[Trevor2]

If you go for the pitch roof option, I agree with DAZB to remove the existing flat roof materials. This will enable you to check the timbers and give easy access to insulate the roof space and fix new rafters to the wall plate.

I would also make sure there are no obstacles in the way from stopping you getting the correct fall for the pitch roof, ie existing windows.

Also you would need adequate ventilation. I reccomend over facia vent strips at eves level and an abutment vent strip that fits under the lead apron at the top of the roof (where your new roof meets your existing house wall).

You could possibly use vent tiles in place of the abutment vent strip but I find them unsightly using them on a low level roof, or air bricks on the gable ends but not sure if you would get enough air flow this way.

Hope this helps.