What chemicals are used in flat roofing?

A couple of weeks ago, I cleaned down and re-stained the deck; I was happy with the job: it was a pretty even finish, using a brand of stain that I've used for a number of years.

Yesterday -- some 10 days after staining, and after intervening rains (which had pooled on top and then dried off with no adverse effects) --

- some light light splotches, of random pattern appeared. It was like somebody had splashed a fair amount of light bleach here and there, which had then dried off.

I'm going to have to refinish and stain the deck (again....), but I'd like to nail down where this splotchy-bleach effect might have come from so that I can avoid it next time.

The only thing out of the ordinary that's been going on when this happened is that my neighbour has a roofing company in, who are putting a flat roof (well, very shallow pitch) over his rear kitchen extension. They've boarded it out; put on the felt; and are out there this morning, presumably finishing it off. (I can hear blow-torches.)

Is there some chemical compound used when putting felt down on flat- roof boards that could find its way from one garden to another, and be caustic enough to created splotchy, lightly-bleach areas on stained wood?

Reply to
Harvey Van Sickle
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Just tar AIUI. Blowtorches will be melting it on to seal things probably.

Reply to
Ian Stirling

Sounds to me as if you've spilt something on the decking which has stopped the stain from soaking in to the timber, and it's washed away from those areas.

Reply to
Rob Morley

On 08 Jun 2005, Rob Morley wrote

Thanks; could be --- I'll explore that side of things when I re-do it.

Reply to
Harvey Van Sickle

On 08 Jun 2005, Ian Stirling wrote

Thanks; I figured it probably wasn't that, but it's the only unusual thing that's happened since I did the staining.

I'll have to explore it a bit closer when I re-do the cleaning/staining. (Sigh.)

Reply to
Harvey Van Sickle

Mates got a similar problem with his decking due to spilt/splashed fat/food etc from having BBQ on decking. When new took stain nice and even, but a couple of years later when he went to restain, stain didn't take to areas/patches where fat and food had been dropped. In fact doesn't look very good, but not a lot he can do about it.

Reply to
Ian_m

On 08 Jun 2005, Ian_m wrote

I think my problem is slightly different -- there's no source of fatty deposits, and I did the same sort of treatment I've done each year or two since I built the deck 6 or 7 years ago. (I clean it down with a pressure-washer a week or two before staining, let it dry out, and then put two coats of stain on it, so there's no residual crud/dirt areas...apart from the dozen or so spots of birdshit which appear during the drying-out time.)

One odd thing is that underneath a small table, one of the pied patches is covered with a light dust-like powder -- like fine, dry mortar which has neither got wet nor blown away. (Looking at the way the new roof is constructed, I'd not be surprised at all to find that they've had to patch some of the brickwork and/or do some fillets.)

I wonder if that could have done it -- that the mortar dust interacted with the relatively-fresh stain, and then blew away from the more exposed spots?

(Dunno....but just in case, I think I'll wait until next door is finished and the roofers have gone before I re-do the deck.)

Reply to
Harvey Van Sickle

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