Future proofing a garage conversion with a party wall.

[AFT4B]

Hi everyone,

Been lurking on this great forum for a while but my first post here.

We are currently having a single-story extension built to the back of the house which will wrap around and join the garage to bring all the roofing to the same level. The garage roof has been removed and walls will be raised slightly to accommodate standard ceiling height and a warm deck roof. This puts our roof higher than the neighbour’s garage. We have to raise the party wall to do this work (party wall agreement already in place).

We are thinking that in the future if the neighbours decide to do the same thing (i.e. a garage conversion), we want to reduce the chances that our roof will be impacted.

The only way I can think of is to raise the party wall by 3 to 4 courses of brick higher than it needs to be for our new roof and finish at the top with coping stones.

I have shown existing and proposed new in the diagram (albeit the wall is single skin).

Is this the best way to future proof or should I be considering an alternative?

 

[accelerator]

Raising the wall is not going to look that great in my opinion.

 

[Deluks]

Raising the wall is not going to look that great in my opinion.

Looking at the blue outline of the existing coping, it seems there's no choice.
Raising it higher as proposed seems to be the sensible option.
There's no cavity so the usual ingress from sometimes poorly built parapet walls shouldn't be an issue.
You'll have to be very particular about vapour barrier, and whilst a warm roof is usually preferred these days, your cold roof might be a better option. Ensure it's vented well.

Make sure your builder knows and understands the spec.

 

[AFT4B]

There's no cavity so the usual ingress from sometimes poorly built parapet walls shouldn't be an issue.
You'll have to be very particular about vapour barrier, and whilst a warm roof is usually preferred these days, your cold roof might be a better option. Ensure it's vented well.

Make sure your builder knows and understands the spec.

Would you be so kind as to explain this for me please?

It's a single wall, do I need to be concerned about the damp coming from the neighbours side given it will be exposed?

 

[jj4091]

If you really want to future proof it have it changed to a cavity wall, by building an inner skin in case of change of use to living accomodation and at the same time rule out any potential damp from your neighbors

 

[AFT4B]

Garages of most 50/60's builds are quite narrow and maximising internal room space is also a key consideration. It's typical to have a stud & ridged foamboard insulation of some description. Cavity wall is not a viable solution for most including us, unfortunately.

 

[stevie888]

Discussion with neighbours required obviously, but this future proofs then too.

I would suggest that their roof covering gets extended up to the coping to avoid any risk of moisture ingress. 2 courses would be enough.

 

[AFT4B]

The neighbours roof cover is the original garage tin roof. It wouldn't be viable to extend their roof covering.

 

[stevie888]

The neighbours roof cover is the original garage tin roof. It wouldn't be viable to extend their roof covering.

One assumes there's a flashing though? I would want to see all the brick covered to keep moisture out as others have said.

 

[AFT4B]

Yes, our roof was felt and the flashing extended onto their roof.

So the intention is to create a parapet with only 2-3 courses of brick and then add appropriate flashing on the neighbours side to make good/ as before.

 

[Deluks]

and then add appropriate flashing on the neighbours side to make good/ as before.

That's what it looks like you've done in the diagram. The red line is their roof covering, the secondary red line being the flashing.

Don't assume lead is to be used, there are cheaper options. If they do decide to convert then they will be redoing the flashing anyway for their new higher roof, even if they don't, then the original tin roof may need replacing at some point in the near future.
My point being, take into account their future plans and the roof condition before deciding what to use.
They may have a preference and be willing to chip in for the cost of flashing on their side, although I wouldn't hold them to it.