Another 1930's no felt roof question

[swebb99]

Hi,

I'm going through the process of buying a detached 1930's property which has a fairly typical roof with no felt. The report said a few tiles had slipped and there was a few bits of light that could be seen in the loft.

I went with my father to take a look in the loft, my father used to be in the building trade but not a builder or a roofer. He said externally the roof looked in good condition, no sag, tiles looked fine. On entering the loft space it was fairly obvious that it was dry, is was very very dusty but in the main looked to be in not too bad a condition. There were however loose plastic sheets in various places that had been stapled to some of the rafters and on first sight I thought they were sagging due to water lying in them, on closer inspection it was dust from the crumbling mortar (tourching ??? only on the edges not full covering) which was on the end of each row of tiles. All the mortar was crumbling away badly and a lot was on the loft floor, mainly on the old insulation.

So in short I suppose a fairly typical 1930's no felt roof.

I'd like to remove the dust, put new insulation in to the loft, have some boarding to put a few things in the loft and obviously ideally not have to deal with continued dust from the mortar but I'm guessing I might be stuck with that.

Now having a read around it sounds like using foam internally is a no no, stay well clear. In general people say if there are no leaks, don't touch. Is there a simple way though of adding an bonding agent on to the mortar that is still in place but crumbling, or if I remove the mortar is there an alternative material I could use to replace it, for instance a quick squirt of foam (not a full covering), something just to hold the tiles and keep some of the potential blown in rain out.

As far as I can see the tiles are held in place via the nibs and there own weight. Does the mortar much help with keeping the tiles in place and if it does should I be worried so much of it has crumbled away.

So basically I'd like to make sure the risk of leaks is minimised, reduce the dust, clear out the existing insulation and add some new and put some boards down, but I'm concerned about the state of the strips of internal mortar on the end of each tile and how I deal with this problem.

Thoughts ?

And thanks in advance

 

[CortinaV8]

Sounds very similar to my old place, never leaked and most of the mortar/back pointing had dropped out. Think it is there to stop dust/draughts in the loft space rather than water.

I stapled tyvec (Because I had a roll spare) to the insides of the rafters all the way round. Seemed to do the trick and stopped the stuff I had stored up there getting covered in dust. I'm sure it's not the proper way of doing it but something for you to consider.

 

[Burnerman]

Typically the roof would have been back pointed ( the correct term escapes me for now) but it was done with lime mortar and horsehair. As you have found, the mortar has largely gone now, and that's typical too.
I'd avoid using foam - even just to hold the slates on place.....the foam often pushes the slates up a bit and it's dead awkward to remove if you need to.
By all means attach sheet material to the underside of the rafters - it will catch the dust and stop the draughts to some degree.
John

 

[Nige F]

Yep it's torching

 

[Burnerman]

Thats the one.....always confuse that with parging for some reason
John

 

[swebb99]

Thanks for the replies I've been a little surprised there isn't a standard easy to use product that is available that you can just, spray, squeeze out rub on in place of the existing of old torching.

I assume this isn't the type of job a standard roofer would get involved with. I will need the roof checked anyway to sort the odd tile out and double check for any issues. I suspect replacing the existing torching would be very time consuming.

 

[swebb99]

One follow up question.

The wood work in the roof appears to be in very good condition so I was thinking that maybe getting a roofer in at some point to felt the roof might be a good plan. The house is a 3 bed detached in the Midlands, what range of prices should I expect for the roof to be felted and either the existing or new tiles to be put on. I'd probably get the two chimneys double checked and guttering/soffits sorted at the same time. Obviously scaffolding would be required to.

Sorry for being a newbie, it's my first house after years of renting!

 

[tony1851]

Sounds very similar to my old place, never leaked and most of the mortar/back pointing had dropped out. Think it is there to stop dust/draughts in the loft space rather than water.

Actually, the mortar (aka 'torching') was intended to keep out wind-driven rain, which can push the water up under the tile.
But missing torching is not usually detrimental and any small amount of rain penetration usually dries off.

And remember that a draughty roof is a healthy roof.

 

[swebb99]

Great thanks for the info Tony. My father has basically said the same thing, his advice was get a local roofer used by some friends and recommended to take a look at the roof with a view to sorting out any minor work that is needed such as putting a few tiles back and checking gutters and chimneys. Ask his opinion on the roof and how long before any major work may be required.

I may in future consider a 4th bed extension that would require roof work so that may be the time to bite the bullet and get the whole think felted.

 

[swebb99]

I've now had a roofer do a bit of work as the roof over the bay window started to leak. The felt on top had basically started to split. He did a good job of sorting that out and I got him to re-felt the kitchen flat roof, lovely job. He also fixed a few cracked tiles, and re-pointed the bottom of the chimneys as he thought water may be getting in there.

I've now used a 1 in 5 PVA water mix on the inside on the remaining torching and that seems to have soaked in to the torching and the crumbling powder is now robust and should stay put a fair but longer than it looked like it was going to.

Next job, remove all old mortar off loft floor, remove old loft floor and insulation and re-do it all. A dusty, time consuming job but well worth it when done.

 

[mikeybikey]

hi there Swebb99
how is your 5;1 pva trick going? is it still in good order? i am thinking about doing something like this, yours should be neary 5 months old now so you should have some view as to if it has been effective. also did you spray it or brush it on, cheers, mikeyb

 

[noseall]

And remember that a draughty roof is a healthy roof.

You took the words right out of my mouth Tony..........

 

[swebb99]

Hi MikeyB,

It's stood up really well. I actually went up there earlier, first time in a month or so to see what damage the wind had done and there was no dust and only one small bit or mortar has fallen off since doing the work plus the odd tiny bit here and there. There was certainly a hell of a draft going through the loft and all the woodwork was dry.

I'd probably go for a 1 in 4.5 mix if I was doing it again because some bits of mortar still feel slightly dusty to the touch however in the main everything feels locked together. Oh and I sprayed it on, I started with a hand pump sprayer but that was slow and kept blocking up. In the end I used a garden sprayer which I pumped up, but you have to be careful not to spray too much with one of those.

I also laid wooden battens on top of the existing rafters do I could lay floor boarding down with 100mm insulation down, board over it and then lay 270 space blanket over that. That was well worth doing. The only issue I have is that some of the space blanket is a little wet but I'm happy that is not a leak problem but some minor condensation when the damp cold air goes through the loft and hits the blanket covering. It should dry out when it warms a little. In the meantime the house is a lot warmer and easier to heat now.

I've attached a shot just before I laid down the final few blankets. When I started the loft looked like a set out of a horror movie!

Hope this helps.

 

[Doggit]

You would have been better off using a stabiliser rather than PVA (which isn't good when it gets wet) as it soaks in deeper. If you redo the roof, rather than felt, use a high permeability breather membrane. And if there's a chance that you might covert the loft space, then add a DPC to the chimneys.

 

[swebb99]

I used pva on a bit of mortar that had dropped off first and it seemed fine when getting wet !