Workshop roof argghhhh help

[billybuntus]

Well.... I'm a bit stuck.

I'm (was) well on the way to having my workshop water tight... well until it rained anyway.

The pitch of my roof is only around 14 degrees, SWMBO wanted the roof to look old so I bought some recalimed slates. Which once on the roof looked great.

However, I was warned that I'd have problems as slate isn't capable of performing watertight roofing dutys at this pitch.

And guess what? They were right. I've thought of sealing the gaps in the tiles with bitumen but after trying it it looks rather bodged (which it clearly is).

So, does anyone have any ideas on a solution which looks attractive rather than galvanised sheet roofing (I hate the stuff) and I'm not keen on a felt roof.

I'm really disheartend and don't know where to go from here.

The reason the pitch is so low is because of height restrictions (the workshop is right up against the neighbours wall so raising the height of the roof isn't really an option.

A rather fed-up,
steven

 

[Waka]

Steven

You could try fiberglass, this looks attractive, well more attractive than a felt roof. The last time I have any done it was about £50 m2.

 

[Paul Chapman]

I'd second the use of glass fibre. We had a bit of a flat roof crisis several years ago and had them replaced with glass fibre because I didn't want to use felt. Very pleased with the result. If I can find the people we used I will post a link.

Cheers :wink:

Paul

 

[Smudger]

A friend of mine had similar trouble with a slate roof on a protected building, so he used his fibreglassing skills to put a thin layer over the whole roof, coloured to look like the slates underneath. No-one seems to have noticed...

 

[billybuntus]

Excellent, sounds like a plan.

Can anyone send me some more info?

 

[Davew2002]

Hi,

This may not be the cheapest solution available, but I noticed you were also interested in something which would last and looked right. I have just completed a workshop (purchased in kit form) which included bitumen tiles, also known as shingles I believe. You often see this type of protection on the side of dorma-bungalows. Having worked with them I can say they are easy to apply, if somewhat time consuming. They are definitely watertight and look really good. I understand they are all the rage in the states where they are used as the primary roofing material on timber frame construction. They have the advantage of being suitable for very shallow pitches.


Here's a couple of web sites for you to look at

http://www.mida.lt/content.jsp;jses...03F2DC?selectionManager.id=FLDID1114527878457

http://www.ruberoid.co.uk/index.php?page=51


They are really easy to apply, don't get too hung up studying the installation instructions on the web sites. It's really much easier than they make out. Once my roof was decked I simply covered it loosely with slaters felt and tacked it down at the hips and eves, then applied the singles over this. I know some often apply the shingles straight to the deck. I just added the base felt as insurance. Oh by the way if you would like to fitter gutters you can achieve this by fixing plastic eves protectors on top of the slaters felt at the eves before covering it with the shingles.

 

[Davew2002]

Ahhhh,

As a newbbie I seem to have transgressed some forum rules. apologies if I have. The URL's in my last post seem to have been quarantined. I will await my fate in due course in the meantime search on Ruberoid Shingles or look at www.mida.it then select ENGLISH (EN in LH side of screen, then Tiles from header)

 

[Paul Chapman]

These were not the people we used (can't remember their name off-hand ) but here's a link to a similar product http://www.grpsystems.com/index.htm In our case, it worked out at not much more than a felt roof but is a much superior product.

Hope this helps

Cheers :wink:

Paul

 

[OJ]

what size are the slates and what lap did you use?

 

[the_g_ster]

Hey, hold on there could be a more simple solution.

What did you use underneath the slates? A layer of simple underfelt would stop bugs, rain, wind and all kinds of problems. I have exactly the same roof as you at almost the same pitch and I lined with a simple breathable liner I got from B&Q.

It worked perfectly, and stops any leakage at all from the effects of even wind driven rain. You need to overlap it by at least 400m accross like tiles and it will be fine, it costs not alot and if you can lift you tiles safely it's the way to go. Coatings over it may well work but may cost more and this is a permanent solution. A slate roof should last more than 50 years if well laid.

Good luck and feel free to shout if you have any more questions.

G

 

[selly]

Do a search on Onduline. Some stuff can look quite attractive.

 

[billybuntus]

Hi chaps,

Thanks for replying.

I've been up to the local roofing place and the advice is replace the roof.

The old guy there insisted that I must have a pitch greater than 30 degrees in order to get a sound roof that won't require underfelt.

So he's given me samples of concrete tile (which actually look ok) that can be laid on a roof down to 12.5 degrees pitch.

So I'm going to do my best to seal the slates with bitumen roof sealant. Failing that I will replace the slates with these concrete tiles.

Oh joy!

Thanks chaps.

 

[cumbrian]

FWIW the roof on our Victorian house is slate, and looks very nice. It doesn't keep the rain out. What stops (or at least used to stop) the rain coming in is the parging - lime mortar applied on the underside of the roof to every slate joint. Has to be lime, I'm told, as its job is to absorb the water that gets past the slates, until such time as it evaporates again. Cement mortar is no good - it doesn't absorb, so the water finds somewhere else to come in. Slates are irregular in shape and thickness, so don't naturally form a watertight cover - there's always gaps for the wind and rain to find.

So the point of all this is that it seems that a slate roof won't be fully waterproof unless there's something underneath it; parging in t'old days, high performance breathable roofing felt nowadays. I know this because a very nice man is going to come in July and take all my slates off, lay felt and put all the slates back again. At least he would be very nice if he wasn't going to charge me about 23 million quid to do it............ So it maybe that the only way you'll get a watertight slate roof is to fit it over decent felt.

As an alternative Kingspan stuff might be worth a look - apologies if someone's already mentioned it. They do a version which looks just like terracotta tiles, but it's in sheet form and insulated. Haven't got a link right now, but Google Kingspan.

Good luck!

 

[billybuntus]

FWIW the roof on our Victorian house is slate, and looks very nice. It doesn't keep the rain out. What stops (or at least used to stop) the rain coming in is the parging - lime mortar applied on the underside of the roof to every slate joint. Has to be lime, I'm told, as its job is to absorb the water that gets past the slates, until such time as it evaporates again. Cement mortar is no good - it doesn't absorb, so the water finds somewhere else to come in. Slates are irregular in shape and thickness, so don't naturally form a watertight cover - there's always gaps for the wind and rain to find.

So the point of all this is that it seems that a slate roof won't be fully waterproof unless there's something underneath it; parging in t'old days, high performance breathable roofing felt nowadays. I know this because a very nice man is going to come in July and take all my slates off, lay felt and put all the slates back again. At least he would be very nice if he wasn't going to charge me about 23 million quid to do it............ So it maybe that the only way you'll get a watertight slate roof is to fit it over decent felt.

As an alternative Kingspan stuff might be worth a look - apologies if someone's already mentioned it. They do a version which looks just like terracotta tiles, but it's in sheet form and insulated. Haven't got a link right now, but Google Kingspan.

Good luck!

Hi Cumbrian,

Before you part with 23 million quid you may want to do a little research.

You'll find that years ago slate roofs were totally watertight without the need for any underfelt. Traditional slaters only user underfelt as a temporary water barrier these days until they slate the full roof.

Have a look on http://www.traditionalroofing.com/TR4_mistakes.html point number 9

these some useful info on there.

Slates become watertight by the over lap over each tile and the pitch of the roof (the steeper the pitch the less gravity and water want to force there way through the slates into your roof space and run down the outside of the tiles).

The whole lime mortar saga sounds like a bodge to me, I could be wrong though.


Thanks,
steven

 

[cumbrian]

Hmmm... Interesting reading - thanks. The roof was fine until last November (although we've only been here 18 months) when we had a combination of very strong wind and horizontal rain, whereupon something in excess of 100 gallons managed to collect in the loft (after I'd put some plastic sheet down to catch it) with no obviously identifiable entry points. I don't know if Westmorland slate differs from the stuff they use in the USA; I also reckon that the felt is probably the cheapest part of the job. One thing's for sure, I don't intend to go down the sprayed foam route - on some of the building restoration fora, Renotherm seems to be as dirty a word as D*do is here! I might now spend some idle time googling parging!

Apologies to all for straying off woodworking topics.

 

[OLD]

If SHMBO must have slate my idea is, sheet and felt with the good stuff (that self seals nails ) then counter batten and batten and replace the slates as the problem is wind blown rain the felt deals with it and the slates work the rest of the time. Roof will only be a sheet + felt+counter batten higher and lighter than if you use concrete tiles should work and felt will be protected from ultraviolet.

 

[RogerS]

Agree with what's been said already.

Your main problem is wind-blown rain ...as you've sussed...because of your low pitch. Your local conditions preclude remaking it at a steeper pitch. So felt underneath, as already suggested, should do the trick. You can get slate nail rippers very cheaply. They slide underneath the slate and pull out the nail holding the slate..with a firm tug.

Beware the concrete tile route. They weight a ton and look naff IMO

 

[dennyk]

why not use felt shingles, they look like slate, only they need a good substrate, something akin to 3/4 marine ply

 

[the_g_ster]

Some good advice been given so far from reviewing the posts.

The key is to relift the roof and pre felt then relay. The problem is the pitch being so low and no overlap is going to combat wind driven rain. Lime is not bodge as has being highlighted, this is an old technique and works very well indeed. Lime is breathable and porous but stops the driving water and remains anchored when the roof moves as all do.

It's worth noting that Lime better suits clay tiles, NOT slate. It looks amazing with small tiles and would really set off any outbuilding above others, it is a skill to use and takes time. The right lime is hard to come by too and there are specialists out there. It's important to note that lime is natural and works great with old buildings. Lime pointing for example actually preserves the bricks as it allows movement, protects against the rain and because it's more absorbant than the brick it pulls water out of them and so saves on the faces of the bricks going and crumbling. NEVER let any silly person builder loose on a house, as if he uses concrete mortar it will seal the wall faces, hasten decay and drop out as soon as the season changes and the building moves.

Concrete tiles are okay but be warned, what your roof company don't tell you as that they don't like the sun and will warp over a few years. Whilst this is fine on steeper roofs, for a low pitched one it will look awful in a few years once a few start to lift and distort the ones next to it.

As already mentioned, slate is a no brainer, its stable, long lasting and looks great. Mad though it sounds you could also consider throwing some compost over the slate into the gaps. In the winter moss will grow, and seal the gaps, and age the building more. Moss will dry out in the summer but should stay put unless the birds use it for nesting, and regrow the following year.