UKC

Good evening all,

I am hoping the collective experience of the UKC community can once again provide some valued and varied advice.

We moved into our current house in 2014. It was built in 1908 and is structurally sound but I noticed, as did our surveyor, that the roofing felt is now perished and looking very sad for itself in places. No leaks, yet!

Other than scaffolding the whole house, stripping the tile (running the risk of damaging the tiles) and re-felting what other options do I have?

I have seen spray foams that are used to make a watertight liner from the inside but have heard horror stories about condensation, limited life span and the fact that is means the tiles cannot be re-used if you decide to re-felt.

I will be inviting roofing contractors to make suggestions and quote but I am keen to go into this eyes WIDE open as it a very big roof, very high and a very challenging shape.

Any ideas, experience or advice?

In reply to TMM:

It's common in sheffield to find roofs withoutany felt at all. As long as the tiles are sound, water isn't getting in and there is ventilation i wouldn't worry about it.

In reply to TMM:

We have owned 2 slate roof houses with no felt and suffered no issues.

I would steer well clear of sprayed on foam for the reasons you mentioned plus there is a high risk of rotting the roof beams etc.

If it's not leaking and your tiles are good I would leave it alone, if you have plans in the future to convert the roof space to a room then it may be worth it.

Davey

In reply to TMM:

we have just re-roofed a house, it's was a little tired, but had done at least 150 yrs on the original slates and lats, no felt. Felt is a back up to the tiles, not essential and in some cases the added ventilation into the rough space and wood, is probably better for your roof.

Avoid spray foams like a person with ebola.

In reply to TMM:

Our roof is slate no felt from about 1890... with spray foam underneath (not done by us). We've just had velux windows fitted as part of a loft conversion, the foam was a nightmare!! We had to scrape it off by hand all around where the velux went in just to get the tiles off. In doing so we found rot around the leaky chimney flashing where water was getting in and sitting on the wood. It would have been much better to have a leak and be able to see it. Had the flashing sorted and the rest of the roof is in good nick but I'd rather not have the foam at all. It is good insulation but it makes more problems than it fixes.

If you don't have any leaks I wouldn't worry about the felt. Just check for leaks from time to time.

In reply to TMM:

Marcus has hit the nail on the head.

Nothing to worry about .

A lot of old roofs here on Hebridean Scotland have no felt.

up until probably 12 years ago we were still using bitumen felt ,which it transpires ,is crap.

Tyvek (etc) breather membranes are a much better job.

In reply to TMM:

Having no felt is probably better than having the old sarking felt any way,all the timbers will be well ventilated which is a good thing.just make sure you insulate the loft properly to stop any drafts and keep the heat in.like the old saying goes "if it ain't broke don't fix it "

In reply to TMM:

Roofing felt is only a secondary line of defence. As people have pointed out, the tiles (if in good condition) should keep out the rain. However, if the felt has gone, it's an indicator of sorts that the roof is past its planned lifespan, so if it were my property, I would be up on the roof to look for evidence of spalling in the tiles and to see if there were many loose ones. People are correct to say that older properties built before the invention of roofing felt are often rain-tight but they may not be entirely weather-tight or insect-proof. When originally built, those properties would usually have been 'torched' (from the French word meaning 'to wipe') with lime mortar on the inside to help keep the wind from getting underneath the tiles. This torching invariably falls off after about 50 years.

If the tiles are sound and you have access from the inside, you could pull out the perished felt and torch the tiles (having first replaced any slipped or spalled ones) using a 3:1 portland cement and soft-sand mix with mortar plasticiser. Most people would not bother, but it's not difficult to do this - you use a pointing trowel, or better a wide, flat-bladed paint scraper and apply a triangular fillet of mortar along the top of each tiling lath.

In reply to TMM:

My last was built 1840 no felt, no leaks, still going strong, slate roof

In reply to TMM:

Thanks for all the helpful and insightful replies, very useful.

There is evidence that some ridge tiles have been replaced but most of the tiles look untouched. There are some signs of spalling given the fragments found in the guttering. What kind of life span can I expect from a clay tile in the UK climate, 100 -150 years?

I will have a look in the loft to see what state the torching is in behind the felt. it is an early bitumen felt that is now very fragile and will not be providing any significant barrier to water ingress.

I am feeling more positive that I might be look at some minor renovation rather than a full roof and back on again job although given the age of the tile this is going to inevitably become more likely.

In reply to Wsdconst:

No....You need a good flow of air through your roof space to prevent condensation and rotting of roof timbers. If you don't know don't advise

In reply to Gael Force:

I doubt very much that's it the original roof. A good slate roof does lst but 175 years is pushing it. I could be wrong though but I vary rarely am.

In reply to jimjimjim:

Hold up, isn't what they are saying correct? They are suggesting keeping the roof well-ventilated, but then insulating the floor of the loft to avoid heat loss from the rest of the house.

In reply to TMM:

If the tiles are good and you're not in a really weather beaten location the felt is basically insurance. Unless and until it becomes a problem I'd be tempted to just keep an eye on it.

jk

In reply to TMM:



Less than that in some instances. Depends on the make of tile and your local climactic and pollution factors. Assuming they're flat, machine-made tiles different sorts have different lifespans - Dreadnoughts, Ironcrete, Rosemaries will all last differing times depending on the clay used and the skill of the kiln operators.

Go up and have a look, but take a few out and look underneath; they can look fine on the surface but the spalling tends to happen on the underside where moisture accumulates which causes the spalling when you get the freeze-thaw effect. You won't see it from inside either because it tends to affect the bottom end of the tile.

They only used to nail every few courses so you can easily edge the nibs over the lath, slide one or two out then push them back afterwards.

In reply to DaveWoody:

Oh yeah....dofts cap and mutters an apology...
next!!

In reply to jimjimjim:
You're an idiot mate, don't talk about what you don't know,current building regulations state 300 mm of rock wool insulation in a loft space.this must not touch the underside of the roof,a 50mm air gap must be maintained. don't tell me I don't know when I have more qualifications regarding building studies than you could imagine mate.moron

In reply to Wsdconst:

Ah ha ha ha.....and breath. I miss read your post and apologise oh qualified one.
Are you sure you have more qualifications than I can imagine though? Because I can imagine loads and loads.
I hope your home is warm....If you own one?

In reply to jimjimjim:
I did see your apology but fancied getting on my high horse for a bit but I fell off.yes I do own a home and it has 300mm of rock wool in both lofts(30mm more than you can actually get away with)as for my qualifications,well laid end to end they'd stretch the Great Wall of china and maybe another 2ft does that blow your mind ?bet your imagination is hurting now trying to picture that.