Are '80's Marley tiles prone to porosity?

fwor

The roof on my house is leaking and I need to get it fixed. It was built in the early '80s, using Marley 16" x 13" concrete tiles, with a shallow roof slope.

As far as I can see, the main cause of the problem is that the felt installed under the tiles is of poor quality (bitumen impregnated hessian?) and was badly installed (too little overlap, plus the builders seem to have dropped debris between the tiles and the felt, causing it to hole in a few places). There are also a few sections where they went a bit wonky as they were battening down, and one of these sections of felt tore and dropped down last year, leading to a leak which needed a temporary DIY repair.

My neighbour had similar problems, and the builder that worked on theirs insisted that 80's Marley tiles were prone to "going porous" and that they needed to have both the felt and the tiles replaced with new.

So... the question: is this true? These tiles are now 40 years old - can they be re-used, or should they be replaced?

fwor

Here's an image of the underside of one of the tiles. Although it doesn't show up clearly, the Marley brand is embossed into the centre of the underneath of the tile:

[Edit: sorry, looks like that didn't work!]

Doozergirl

I don't believe that for a second but there are others more technically minded than me!  

Porous suggests it's like wearing a plastic coat vs wearing a cardigan.  

It's gravity that stops a roof leaking.  Gravity with the back up of your membrane for any water that gets blown under the tiles.   Roofs don't leak because tiles are porous, they leak because tiles might slip or even crack/break but not because tiles get 'porous'. There's plenty of air up around tiles for them to dry out after a downpour.   


Goodness knows how many roofs are simply replaced with the same tiles and maybe a few reclaims. 

FFHillbilly

life span of them is 50 years so seems a bit early to be worrying. and no they should not be reused again, but anyone would find that out once they realise most of them break when trying to remove them carefully!

stuart45

How long do intend to live in the house?

plumb1_2

Yes they can because porous, you only need to remove a old concrete tile after it’s been raining to see water beads underneath. But if it’s got a good quality felt underneath it shouldn’t be a problem.

I replaced my roof because of just this issue, old bitumen felt and porous Redland concrete tiles.
I had a full scaffold around my house at the time doing the facias and soffits, so took advantage 

fwor

Thanks - I share the view that the neighbour was taken for a ride - theirs was done 10 years ago when the tiles were only 30 years old!

stuart45 said:

How long do intend to live in the house?

Good point - I have no plans to move, so I might be here 2 more years, or 20 more years.

I've also seen beads of water underneath, but it's never completely clear whether that is water coming through or condensation.

Ok - so the general consensus seems to be that even if there is a little bit of porosity here and there, the new membrane should be enough to counter it (i.e. to carry it down to the edge of the roof).

I will of course have to budget for a percentage of broken tiles, I guess, but secondhand ones don't seem to be very expensive.

fwor

FFHillbilly said:

life span of them is 50 years so seems a bit early to be worrying. and no they should not be reused again, but anyone would find that out once they realise most of them break when trying to remove them carefully!

Ah - I didn't read that reply properly. You're saying that I should expect most of them to break while being removed??? I hadn't expected that, but I've never tried to remove one, so I don't know!

FFHillbilly

fwor said:

FFHillbilly said:

life span of them is 50 years so seems a bit early to be worrying. and no they should not be reused again, but anyone would find that out once they realise most of them break when trying to remove them carefully!

Ah - I didn't read that reply properly. You're saying that I should expect most of them to break while being removed??? I hadn't expected that, but I've never tried to remove one, so I don't know!

maybe an exaggeration to say most will break, but some will break. It's almost certainly not worth it trying to re-use 40 year old tiles though

fwor

Agreed - some will break and will have to be replaced, but ditching them all is a lot of tiles to throw away.

I confess I haven't counted and it's dark out there now, but I guess there must be 500 tiles on there. So that's at least a couple of grand's worth of tiles to chuck out, plus the cost of enough skips to take them away. It seems a bit wasteful if they are maybe only half way through their probable lifespan?

stuart45

Get some estimates for using new and the old tiles, and then decide.
Once a roof is felt and battened, it's watertight, so even with old tiles it will last the lifespan of the membrane. It has been said though that the lifespan of a membrane is reduced by leaks.
Concrete is a porous material, so even new ones have a certain level of porosity. As they age, they can develop tiny cracks with constant temperature changes, freeze/thaw, hail, getting walked on etc.
The Building Reserch Establishment were once asked to look at some older roofs, and stated in some cases that were some in good condition at 60 years old.