Sandstone bay window - how to repair?

[Jasknya]

I am currently carrying out some maintenance on the bay window of my house. My house is approximately 100yrs old (Edwardian) and the bay window is constructed from sandstone.
It seems that during a previous maintenance session the parapets at the top of the bay window were repaired using mineral felt. The problem is that this felt seems brittle and there are cracks and holes in several places. I have included some pics to illustrate the problem. As you can see from the pic. the sandstone is also cracked and loose. Is there a way of fixing it in place?

I have had a roofer out as I suspected the flat roof of the whole bay window needed replacing, however he informed me that the roof is fine and I think he said the cracks in the mineral felt can be repaired with silicone. Is this right? If so, what type of silicon and how do I apply it? Are there any alternatives. Ideally I would like a tidy repair that looks like the original sandstone, is this possible with silicone?

Thanks
David

 

[Alastairreid]

Forget the silicone! and forget that roofer as well! there should be a lead apron in there.
the sandstone can possibly be repaired using lime mortar.

 

[Jasknya]

Hey, thanks for the reply. If we were to have the whole roof done, you're quite right. We actually had four quotes and the first three all said that the the way the roof had been done previously with the felt was a cheap solution. To re-do the roof they all quoted in between £300 and £700.
The reason why we had the quotes in first place was because we suspected a leak as there are water marks on the inside of the bay window, although we've never actually seen water. The guy who told us that the roof didn't need replacing said that the leak was most likely caused by several slits in the felt (as if someone had dropped a chisel) that could be repaired with roofing sealant. I think he also said the mineral felt could be repaired with sealant. This chap came highly recommended from a friend and we also felt that as he hadn't taken our money, his advice could be trusted. He advised it would be worth trying this before shelling out.
Out of interest do you know where I can get some lime based mortar. So, where to from here?

 

[SASroofer]

I wouldn't put alead flashing into single brick work, far better to cap the roof in felt, and that roofer is a muppet, silicon for gods sake!

 

[Alastairreid]

I wouldn't put alead flashing into single brick work

eh!!!! its a better solution than existing.

 

[Alastairreid]

far better to cap the roof in felt

felt on top of sandstone?

 

[SASroofer]

Yep, if you chase into a single skin and wedge the lead theres a chance it may split the sandstone, and a decent grade torch on capping sheet applied correctly would be a far better solution because it would seal the top of the sandstone. Possibly use an alloy or grp trim to the outer edge though, to allow a drip edge.

 

[Alastairreid]

reconstitute the sandstone blocks and fit the apron....what do yo think?

 

[Jasknya]

Hi! I'm getting a little confused keeping up with the thread of the conversation (excuse the pun ), so I decided to throw another picture to illustrate my confusion.

Can I ask are you both roofers by trade? Thought throw something else in too. Someone else has suggested using a glass fibre tape and epoxy resin - not quite sure how that works? And possibly fixing the sandstone with stainless steel rods inserted through drilled holes in the top of the sandstone.

Thanks again

 

[ladylola]

reconstitute the sandstone blocks and fit the apron....what do yo think?

That's what I'd be inclined to do.
Looking at the second picture the weathertightness is entirely dependant on the felt sticking to the stone, there is a potential point of water ingress at the top edge of the felt.
How deep is the whole thing , i.e. from the base of the roof to the lower part of the "battlements" as it may be possible to fit a flashing lower down, or , to cap the wall with a lead cap dressed over the top.
As to the stone repair stainless rods are a good method ( we do this a lot on heritage jobs) using a resin to fix it. The resin will actually glue the stone back together as well and any cracks can be pointed up with a lime -stone dust mix to blend it all in. You will need to be careful drilling the stone though, hammer action is a definate no no.

 

[Alastairreid]

i would cut the corners square, dress a lead apron over the wall and fit coping stones.

 

[SASroofer]

i would cut the corners square, dress a lead apron over the wall and fit coping stones.

After seeing the 2nd photo, I agree with this

 

[Jasknya]

i would cut the corners square, dress a lead apron over the wall and fit coping stones.

Sorry peeps. Now I'm completely lost???

Do you mean cut the battlements off entirely?

How deep is the whole thing

Ladylola, I'll post take some more pics tomorrow and have a look.[/i][/u]

 

[Jasknya]

How deep is the whole thing , i.e. from the base of the roof to the lower part of the "battlements"

Ok, now I've been up on the bay window again and measured the above and it is between 18 and 24cm. I've also taken some more pics to hopefully give a better context.

What do you think?

 

[Alastairreid]

I think its not a difficult fix for a roofer!

A lead apron correctly installed is what you need.

There's a few different ways of doing it.

Remove the battlements, dress sheet lead over the wall and fit coping stones.

Remove the existing mineral apron, raggle in a lead apron, install a bellcast bead and render.


Or install a lead apron along the line of the existing mineral felt.