hi im thinkin of building a conservatorie on a detached bungalow how big can i go with out planning and can i put a slate roof on to tie into the exsisting roof

If your putting a slate roof on, you might need planning. Best to get an architect or conservatory company out to advise you, they might even have their own in house architect/designer.

The general rule of thumb is; if your conservatory is built with 70% see through materials ie. glass or polycarbonate, you do not need planning permission. Putting a slate/tiled roof on would bring the area down so you would need planning permission. Your local authority will let you know how big you can build it as it can only be a percentage of the total ground area of the property. Hope this helps.