Need a second opinion on my garage roof

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chunkybeats

45 posts

Geek

# 181350 12-Oct-2015 12:10

Hey guys,

Just need a 2nd opinion on my garage roof. I bought my house 2 years ago and have noticed over a very short period of time that the falls on the roof are non existent. Also the joists are rotting and the bottom plate in one corner is nearly gone.

I have put some H1.2 treated 4 x 2 blocking under just to try and support the joist.

Now the roof is a walkable roof which is constructed in a granule based butyl membrane. In my mind it is failing at the joints causing the water to pool over 2 days.

I cant afford to reroof the garage at the moment and was wondering a temporary solution for the joints. I have heard that lap tape could be used between the butyl sheets, im just wondering can I install it myself ? or would I need a roofer to do this? Have any of you guys had this problem before? Luckily its not in my house and its only the garage but still its a bit messy after heavy rain.

blackjack17

913 posts

Ultimate Geek

# 1404263 12-Oct-2015 12:22

Some photos might help.

H1.2 is only good for dry internal use, if it is regularly getting wet esp for extended periods then it will rot

chunkybeats

45 posts

Geek

# 1404272 12-Oct-2015 12:44

Yeah Im aware of the blocking is not high enough timber treatment. I will replace with H4 timber.

Here is a photo of the deck above.

kiwitrc

4123 posts

Uber Geek
Inactive user

# 1404318 12-Oct-2015 13:35

Probably want to use this http://www.enviropaints.co.nz/shop/Enviropaints+Butylcote/BUTYLCOTE+WHITE+%26+BLACK.html to seal the butyl.

I think however the bigger issue may be that its been back filled against the walls of the garage. It would take some serious water proofing to stop water penetrating the garage in that case. I also suspect that if its been backfilled and wasnt designed to be, the timber will be boric teated at best and is going to rot. Might pay to see what the plans/consent stuff say at council.

blackjack17

913 posts

Ultimate Geek

# 1404320 12-Oct-2015 13:40

Where it has been backfilled is it brick?

chunkybeats

45 posts

Geek

# 1404321 12-Oct-2015 13:43

Yeah the garage was built in 1982 so its likely not treated timber at all. As for the consent / building information I think I have some plans but again there wouldnt of been a consent issued for it due to its age.

Thank you for your advice, I will try that liquid membrane you recommended, it should protect it for another couple of years all being well.

chunkybeats

45 posts

Geek

# 1404322 12-Oct-2015 13:44

It is concrete block, so probably been back filled at the back. Although when a huge downpour occurs, water gets through the concrete block walls as well as the roof.

mattwnz

15269 posts

Uber Geek

# 1404334 12-Oct-2015 13:52

I don't think the roof fall is a problem, although the roof looks to be pooling. But if the membrane isn't leaking then it shouldn't be leaking If it is, then you would need to get the membrane replacing or repairing. Prior to the 90's I don't believe you needed a fall on a membrane roof. I suspect your problems is more to do with your retaining walls, and moisture getting through. Is is possibly related to the drainage off the roof, so you should make sure any water from it goes into a gutter and shed well away from the building.

mattwnz

15269 posts

Uber Geek

# 1404337 12-Oct-2015 13:56

chunkybeats: Yeah the garage was built in 1982 so its likely not treated timber at all. As for the consent / building information I think I have some plans but again there wouldnt of been a consent issued for it due to its age.

Thank you for your advice, I will try that liquid membrane you recommended, it should protect it for another couple of years all being well.

I believe there should still be a building consent in the 1980's. If not, then I would be concerned. Did your lawyer check all the consents were in place prior to purchasing? . Also it should have used tantalized timber. Untreated timber was mainly used in the 90's with lots of kiln dried stuff being used. The problem is moisture, and not whether the timber is treated or not, as even treated timber will eventually rot if it is damp for a long period of time.

mattwnz

15269 posts

Uber Geek

# 1404340 12-Oct-2015 13:59

kiwitrc: Probably want to use this http://www.enviropaints.co.nz/shop/Enviropaints+Butylcote/BUTYLCOTE+WHITE+%26+BLACK.html to seal the butyl.

I think however the bigger issue may be that its been back filled against the walls of the garage. It would take some serious water proofing to stop water penetrating the garage in that case. I also suspect that if its been backfilled and wasnt designed to be, the timber will be boric teated at best and is going to rot. Might pay to see what the plans/consent stuff say at council.

From the photo, it looks like it is bitumen, and not butynol. Also it doesn't look like the membrane is all that old. Although the photo isn't great, so maybe mistaken.

kiwitrc

4123 posts

Uber Geek
Inactive user

# 1404346 12-Oct-2015 14:05

Actually considering its a traffic area appears you need something like this not the one I linked to https://secure.zeald.com/enviropaints/results.html?q=sms+a

chunkybeats

45 posts

Geek

# 1404355 12-Oct-2015 14:12

Actually this is the product that was laid in 2006. http://www.bitumat.com/rj/index.php/products/list-of-products/polyflame . There is a warranty but i suspect I will be covered as it was the applicator who should of allowed for the falls. Hmmmm a strange one.

I will have a dig out and see if there was a consent. Im going to need to do something cheap and quick to temporary repair the roof. The walls are not as bad as the water coming through the roof. I do think a gutter will be needed although if it was me I would re fall the roof out to a gutter on the other side.

Thanks for your replies guys.

kiwitrc

4123 posts

Uber Geek
Inactive user

# 1404358 12-Oct-2015 14:18

There you go, you can seal it with a blow torch, or burn your garage down ;)

I would expect it to last more than 9 years.

chunkybeats

45 posts

Geek

# 1404364 12-Oct-2015 14:25

haha thanks kiwitrc I dont think I can trust myself with a blowtorch!!!

blackjack17

913 posts

Ultimate Geek

# 1404430 12-Oct-2015 14:55

If you just want cheap and easy what about just putting down a sheet of polythene. It isn't a permanent fix but will stop water coming through and let you draw up some plans/save some cash.

You can get it up to six meters wide, 100% waterproof

http://www.trademe.co.nz/building-renovation/building-supplies/other/auction-962097642.htm

chunkybeats

45 posts

Geek

# 1404762 13-Oct-2015 08:26

Thanks blackjack! Not too sure it would hold down well in a Welly wind!

Would this work to temporary seal the lap joints in the bitumen?

http://www.bunnings.co.nz/bear-flashtac-weather-proofing-foil-tape-48mm-x-3m-silver_p00730279