Semi detached roof height

[Janecw8]

Hi all,

 

I'm looking for some advice before approaching architects or structural engineers.

 

I've recently bought a semi-detached house that needs quite a bit of work. There is an existing single-storey side extension off the original kitchen (which has a hipped roof), creating a dining room at the rear with a flat roof. Both the kitchen and the dining room roofs need replacing, as highlighted in the survey.

 

The flat-roofed extension is joined to my neighbour’s identical extension. I’ve attached a photo of the house (with a rough yellow line marking the boundary between our properties) and the floor plan

 

Here’s what I’m hoping to do:

* Remove the wall between the kitchen and the dining room
* Widen the opening on the rear wall
* Raise the kitchen ceiling height to match the dining room ceiling.

 

My concern is this:
The current roofs don’t meet insulation regs. I’d like the RSJs hidden within the ceiling, but I don’t want to lose any ceiling height inside. This likely means raising the entire roof level, which would result in my roof being higher than my neighbour’s.

 

I understand this would require planning permission, but from a practical construction standpoint, is it doable?

 

Additionally:

 I would prefer a mono-pitched roof, is that possible given the fact the extension is joined to my neighbour’s. (If a mono-pitch isn’t feasible, I’d accept a flat roof.) 

 

Any thoughts or experiences with a similar setup would be greatly appreciated. Also, if anyone can offer a very rough cost estimate for this kind of work (I'm in the North West), that would be fantastic.

 

Thanks in advance!
 

[Mr Punter]

Given the low first floor window cills you are probably going to end up with a flat roof.

 

You could build your roof up higher than your neighbour, putting the insulation on top of the decking.  If your neighbour wanted to do theirs at the same time it may work well, but not essential.

[Adsibob]

Rather than raising the roof height, have you considered dropping the floor? Wet did this and gained about 45cm in height. We also replaced the timber floor with a cement slab onto which we added insulation and then UFH within screed and then finished the screed with microcement. It was a big job, but has transformed our ground floor. We now have very high ceilings for a 1930s semi.

[Adsibob]

26 minutes ago, Adsibob said:

Rather than raising the roof height, have you considered dropping the floor? Wet did this and gained about 45cm in height. We also replaced the timber floor with a cement slab onto which we added insulation and then UFH within screed and then finished the screed with microcement. It was a big job, but has transformed our ground floor. We now have very high ceilings for a 1930s semi.

To clarify, we lowered the height by about 29cm or 30cm in the front of the ground floor (ie where our hallway, front reception room and WC are) whereas we lowered the height of the back half by about 45cm, so although all the ground floor benefits from higher room heights, the effect is more pronounced in the kitchen, back reception and dining area as well as in the utility room. This does mean we have a step down from our hallway, but the architect did a really good job and so it ends up zoning the different areas of the ground floor really well. Another advantage is our lower ground floor is at exactly the same height as our rear patio/garden which makes for a really good transition when the sliding doors to the patio are open, as there is effectively no change in floor height between inside and outside.

[Janecw8]

Thank you both so much for the replies, I have been googling all sorts to try and get it straight in my head....was getting nowhere fast! 

 

@Mr PunterI had completely overlooked if I raise the roof, the available pitch probably wont be sufficient for anything but a flat roof due to the low first floor windows, thanks so much for clarifying that a different roof height to neighbours is possible I just couldnt figure it out as the extension was obviously done on both properties simultaneously. Really appreciate this 🙏

 

@Adsibob very interesting, honestly I am not sure how that could work, as the other parts of the downstairs and the dining room actually already have fairly tall rooms (2.6m) and I would like the floor to be level. Did you lower the floor in the whole downstairs? I actually do need to lower the floor in the kitchen& dining room or raise the floor in the rest of the house as there is currently aprox 5cm difference and it drives me crazy. 

 

I definitely think I have bitten off more than I can chew with this 🫣

 

 

[Janecw8]

@Adsibob thank you that make sense... Definitely something i need to consider as there is a step down to the patio which i had only considered raising. I think an actual step may not be too bad... Its the current small lip that bothers me 😁 much appreciated again 🙏