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Re-roof or spray foam????

Postby alial » Sun Apr 13, 2008 6:51 pm

We have just bought an 1870's house which has an old slate roof without any felt, just mortar stuck to inside of slates (torching?). It leaks a bit, one chimney has no flashing. some slates have slipped and there is a bit of a sag visible in the structure.
It clearly needs repair, we can't decide between the options:
1. patching up the roof and then a DIY spray foam kit, or
2. patching up the roof and then professionally applied spray foam or
3. a complete re-roof, salvaging some of the old slates and fitting felt and new battens etc.
We have a limited budget but want the best for our house.
Roofers recommend new roofs, spray foam companies recommend foam, it's hard to find unbiased advice on this topic, please help.
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Postby Perry525 » Sat Apr 19, 2008 11:59 am

The first thing to do is, go up in the loft and take a careful look at the timbers and slates, look for signs of wet wood, look round the chimney to see if its wet, look up to see if the flashing is in place.
If you find signs of wet wood, go outside with a pair of binoculars and check all the roof that you can see, for slipped, cracked or missing slates.

Now you have an idea of the state of your roof.

Better still use a ladder to take a closer look!

The English language is an interesting thing, it is very easy to misunderstand a verbal description, when you are not familiar with the thing in question, you could end up paying a lot of money for work that is not necessary.

If I understand correctly you are writing to say that your roof was made in the 1870's and while it has sagged because the timbers were not sized correctly, it is in most respects still sound?
A slate roof may be expected to last for four hundred years.
In that time, one can accept that some nails will rust and need replacing, and the wind will have rattled some of the slates a few thousand times and some of the softer ones will have enlarged holes causing slates to slip.
All that is normal, as is the practice of torching, where wind blown rain is forced up between the slates and torching helps to overcome bad design.

A well designed roof takes into account the hight and exposure of the building, and allows for wind blown rain. Preferably, by making the roof steeper or by increasing the slate overlap, thereby making it harder for the wind to push the rain into the building.

None of which would lead me to expect that the whole roof needs repair or replacing.

If you are OK with heights and have the correct gear, get up and fix it. Or get someone in to repair it, looked after it will go on for many more years.
When your house was built, most builders did not have access to waterproof materials except for copper, which has always been expensive and lead.
Houses were not made of waterproof materials, merely of bricks, slates and tiles. Things designed to shed water, it was accepted that some water would get in, but they were designed to dry out with the effects of wind and rain.

You mention spray foam, this is the flavor of the year in the USA and Canada, as it has the best and most permanent insulation properties, far better, far more reliable than fibre glass.

Some people in this country don't like it.

Used on the underside of a roof, it can disguise leaks and lead to wood rot, where the rain gets in and because all the holes are sealed, the wind cannot get through and dry the wood. A lot of roofers don't like it, as its hard to remove and makes repairs harder.

I would not use it for this reason, however, if you want to use it to keep your home warm then by all means pour it between the joists of your ceiling, where it will do a very fine job.
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Postby chris_on_tour2002 » Wed Apr 23, 2008 2:12 pm

i want to install a plume management kit to the exhaust flue of my boiler. the outlet is about 18 inches from the soffit on the first floor of the house. my neighbour is not happy that, with the wind in the right direction, the plume blows across her window.

the plume management kit consists of a pipe, about 3 inches and 3 feet long. it will go vertical but will foul with the roof. so i want to drill a hole 3 inches in diameter in the soffit and then another one in the roof tile above so i can pass the pipe through. is this possible?

the roof is tiled, not slate, and i want to make it watertight afterwards. any ideas?
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Postby jonb » Fri Jul 25, 2008 7:57 am

New to the forum so sorry its an old thread.

I had my roof urethane sprayed 4 years ago, the company that did it came with testimonials, a nice website and a national ad campaign, but I've had and still have big problems with it.

part of their offer is to make good the original roof and offer a 30 year guarantee. My flashing was patched and has progressively failed leading to water literallly running into the roofspace down supporting joists on both sides.

No conventional roofer will touch it and this roof companies own rep has looked at it and told me the flashing is completeley had it its been patched more times than this lot have been back to it, so was not in 100% good order before they 'made it good for 30 years' - it wasn't replaced at the time and failed initially within 2 years of urethane installation - patched again! - that doesn't say much for their skill at diagnostics or their competence/desire to actually make the roof good for the 30 year guarantee.

Apparently it'll need at least 3 days work to remove and replace the flashing entirely in decent weather - so I've been living with the latest leaks for over 6 months now through this sodden spring and summer.

Also I'm in the market for a loft conversion and it has dawned on me that I have no way of getting the steel flooring joists up there, I'm in a semi with limited clearance to my detatched side. The usual way is through a hole in the roof and since mine is now one single plasticised entity I'm a bit stuffed unless I can fit them through the Velux that we had put in when they sprayed the roof.
It's also going to need cutting and smoothing down where its splashed over joists and expanded deeper into the loft between them to allow for them to be boarded over, or any resultant room will have a lovely golden yellow snot like ceiling that wouldn't be out of place in a Dr Who monsters bedroom.

Insulation wise its great, the roof still creaks and groans in the wind but nowhere near as much as a conventional, The slates do seem to be very secure and none have come off or shifted in the wind, the joists look in pretty good nick, even for a near constant stream down a couple of them and I fear a fair bit of invisible water ingress down the nails and any other little nicks they may have left up there.
Also it was a lot cheaper than a complete re-roof or the significant overhaul needed.

That said tho, I'm now completely over a barrel for repairs and dependent entirely on these people to come and fix it, something that they've shown no inclination to do so far, it took 3 months of badgering them to get someone to come and look at it and basically tell me to shut up and go away until the summer, I'm just about ready to start the fight to actually get them here to do a guarantee fix - I don't hold out much hope of that being quick or easy.

A surveyor acquaintance was very uncomplimentary about urethane roofs and warned that it has stripped some value from the house as they are still pretty unusual and an untried unusual entity over here as well as being so hard to fix if there are problems.

I'd have had less sleepless nights and far far far less hassle if I'd paid a few grand extra and gone for a conventional roof solution.
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