House Guttering, slope, sealing

[JohnR]

We have stainless steel concealed gutters in our house. These would be fine if the joints didn't leak (the gutters are 3000 mm long). As the gutters are concealed, this means that water flows back onto the fascia, and a couple of bargeboards have also rotted.
My problem. I've had conflcting advice from an architect and some builders/roofers. One says replace the concealed gutters with external gutters, but this involves squaring off all trusses, etc. Others say replace the stainless steel with colorbond or similar, leaving the box gutters (which we would be quite willing to do if it would really fix the problem). Another builder (a friend) says don't replace stainless steel but use Sikaflex on the stainless joints. (it was the search for Sikaflex that brought up this BB in terms of marine hatches - but that BB talks about using either Sikaflex or other types of seal). Does anyone have experience with this problem and/or give any advice please? Do concealed gutters need more that 1 in 100 slope, for example? If so, how do you either shave the rafters or add shims to improve the slope?
Many thanks
JohnR

[journeyman Mick]

John,
this is why I hate box gutters and try to talk people out of them . If you can fix them by resealing then obviously this will save a lot of time, money and grief. Be aware however, that the sealant will break down over time and may need to be replaced after a few years, maybe as little as 2, possibly as many as 15. If you want to reseal, you'll need to remove any old sealant that's visible. (the sealant should only have been in the lap where it shouldn't have failed) All those bits of old sealant will be holding water which will cause any new sealant to fail.
After you've peeled, scraped and scrubbed all the old goop off use a hot air gun (or a hair dryer at a pinch) to dry the joint out. Use the appropriate sika primer and sealant as per instructions. Try www.sika.com.au (don't know if it will work, got it off the back of an old catalogue). There are other polyurethane sealants around but Sika seem to have the greatest range and you're not going to be using that much of the stuff, so it's worth going with what's tried and proven.
The trouble with using minimal falls in gutters and roofs is that any settlement of the building or different shrinkage rates from one rafter to another can require the water to run uphill to get out/off . Without seeing your house I'm only guessing, but I'd say that trying to refit the existing gutters is going to be a lot of work. I'd try to reseal them. If that doesn't work you'll have to toss up between pulling them out and refitting them with more fall and sealed properly or cutting back your roof edges and fitting conventional gutters. (Aesthetics V Function) Of course you could always fit custom made stainless half round gutters and have both function and aesthetics (and a big hole in your bank account :eek: )

Mick

[bitingmidge]

Assuming that it is the joints in your gutters that are leaking, and they are adequately sized, have overflow provision and properly flashed (all of which are criteria for I use for designing box gutters), I am going to have a rare and minor moment of half-divergence with Mick!

I don't think you can easily re-seal the joins. You do need to follow all the directions he gave, particularly with regard to cleaning and the use of primer. The gutter will have to be lifted, dismantled and the laps cleaned and re-sealed. If that is done properly, the sealant will not be exposed to UV and will (should) live more or less for the life of the metal.

Just bogging over the top of them won't do for more than the next summer.

A 1:100 fall shouldn't be much of a problem notwithstanding that it's terrible practice, if the leaks can be fixed.

I think anyone who has been in the building game long enough will have a pathological dislike for box gutters, and we all have our secret details which always amount to overdesign to avoid these issues.

For me, no joins in the gutter. That means for a three metre length, a sump at one end, and a turn up the other with an overflashing to make an expansion joint...downpipes at 6000 maximum centres, no bogged joints.

Make sure that it won't overflow and fix it properly...it'll be the last time you'll have to!
Cheers,

P

[jackiew]

of course the unethical minority would just replace the bargeboards with new ones when the warm weather arrives and move house quick )

[journeyman Mick]

Midge,
I agree with your procedure on how to fix it properly, unfortunately it involves taking up all the roof sheeting (unless it's tiles of course), and removing all the over flashings, and possibly a lot of the barge and cappings etc etc etc. Of course if the sealant had been properly applied in the first place this shouldn't be neccesary (to quote one of my clients, who has become a good friend, ex US timbercutter and builder " If, if , if, if only a frog had longer legs, he wouldn't bump his ass so much"). If it was my place I'd probably take it all apart and redo it properly, or I'd take a chainsaw to the end of the trusses/rafters and redo it all with conventional gutters. :eek: .

Mick

[julianx]

I think we need a new forum called "Ya know what I hate"
There's only one thing I hate more than box gutters and thats idiots that cut the back of quad gutter down so it over flows into the house instead of into the garden.
If it were my place I would do one of two things, change the lap joints into expansion joints as midge described and put in extra down pipes or I'd consider cutting the roof back and fitting new fascia and fascia gutter.Its bad enough to design a house with a box gutter at all let alone putting where a fascia gutter could have gone, I hate box gutters.
If you do reseal its a good idea to put two beads of sealant in the underlap.

did I mention i hate box gutters

[bitingmidge]

No argument with you Mick! We're singing from the same hymn sheet, only I'm just singing the chorus!

Or you Julianx...except that the idiots that cut the back off quad gutters are more often than not the factory, and they've sold the great unwashed on the fact that it's a good idea!!

Had a quiet philosophical debate about this with a builder yesterday in fact. For some extraordinary reason, fashion now seems to dictate that one mustn't see the wavy edge of the roof sheeting. (Probably because roofers are too lazy to keep the insulation tidy). It is now preferable to fill your house full of water.... anything but see the edge of the roof sheeting.

If you must use that stuff, please make sure that it has an exaggerated fall so that a big heap of it near the downpipe is lower than the back of the fascia so that it can overflow somewhere!

And for those that think the piddling little slots for "overflow" in fascia gutters work: stick a tennis ball in your downpipes one day, and run a hose in the gutter...

With that off my chest I can get into my shed and do stuff now.....!!!



P

[Ian007]

Problem is that most if not all architects design for looks and thats why we end up with the worst possible solution for water runoff BOXED GUTTERS :eek:

Working on or in a roof most days must say i have never seen a boxed gutter that didnt rust out or hold silt in a low spot that will one day rust out or just plain leak.

but it does help if the boxed gutters are put in with enough fall in the first place. ive done a few replacments of them and havent had any problems. (not to self touch wood)

Cheers Ian

[IanA]

It's good to see such thorough and unadulterated hate of box gutters.

They are the devil's most successful building product!!!

[soundman]

A word about re sealing.
I once worked at a place that built truck bodies, they built this mobile libruray, it leaked!!!
several blokes had several goes at resealing it on several ocasions, & failed.
this failure was because they didn't dismantle the joints before resealing.

[rsser]

My pa had this problem, and this is going back years but from memory he found a kind of membrane he lined the gutter with that worked. Sorry I can't be more specific.

Good luck!

[capedcrusader]

If you do reseal its a good idea to put two beads of sealant in the underlap.

I just like to add that I read that the air pockets trapped between 2 lines of sealant when the joint is lapped can expand and damage the seal so be careful not to entrap air.

[seriph1]

I believe there is a product available here in Oz (certainly in the states) that is called Bituthane tape - it comes is widths up to 450 I think, and is used as an edger in flat commercial rooves - tops of building type applications - the easiest way to address this problem could be this stuff ..... 50 metre roll, laid along the box gutter (pigs of things) in a single piece, formed and folded in, using a heat gun or dryer ..... can't attest to the application, but have seen it in situ on Planet-los-angeles and it seemed very robust. Even if joined, it is done with heat and forms a melded single piece I believe......... just thinking abt it more, they workers may have used a torch.....

Cheers

ps. I envy you NOT!

[JohnR]

Absolutely astonished at the prompt erplies to my original query - I gather that some small percentage, like me, don'y like box gutters!!! Much food for thought, including membrane seals, etc. I assume you would all go for about 1:100 fall - what worrie3s me that in a 15 m long side, that's about 15000/100 = 150 mm, even if they fall to the centre that's still around 75 mm (3" in old units). One of the other forums (I can't find the ref but it related to bonding stainless hatch on a boat), mentioned other types of seals in addition to the polyeurathane based ones - but is Sikaflex still the preferred bond?
Many thanks.
Johnr

[Sturdee]

I believe there is a product available here in Oz (certainly in the states) that is called Bituthane tape

Steve,

Is that the same as the asphalt tape called Flashtec.

I have used Flashtec tape to repair holes in corrugated iron sheets and roof gutters. I would use that to seal the joints in the box gutters, at least as an interim measure untill you decide what to do. ( If ever )


Peter.