Issues with newly built flat roofed garage

Joined
29 Sep 2016
Messages
11
Reaction score
0
Country
United Kingdom
We just moved into a new place with a flat roofed double garage.
Roughly 5.8 x 5m with a fiberglass(?) roof.
We've spotted a few issues with it:

1. Water pools on the roof
SOVd5hT.jpg

From my calculations it has a fall of 1:128 and on the lower edge there is a bit of a lip that holds the water back. It's probably only 2-3 years old and the top layer of fibreglass is starting to flake off, but no signs of leaks yet.
I assume we will encounter issues in the future, what are the options to remedy this?
My first thought was to just raise the front of the roof to bring it up to 1:80 fall but looking at how it was constructed I think the entire roof would have to come off as everything is screwed in from the top/under the fibreglass.

There are 2 joists spanning the length of the garage meeting in the middle supported by the girder. Secured together with screws.
9Yu6BUU.jpg


The joists at the front sit on top of these horizontal parts sat on the blocks.
Joists are secured from the side into the horizontal parts below them.
RO7u4UA.jpg


Similar at the back (lower part) of the garage but only 1 horizontal board. I think this is where the fall comes from.
QYr1hYR.jpg


Any ideas if I could remedy this from inside?
Would there be a solution from outside/above? Redo the fibreglass with more of a fall?

2. Water gets behind the guttering
This was caused by me sweeping the water off the roof.
fVTCJxK.jpg

The fibreglass roof doesn't overhang enough so some of the water misses the guttering. This causes some big damp patches and white/salt marks inside.
UJEhoT1.jpg

Looking up there, it seems someone has stuck some lead up between the fascia and the lip of the roof so all water is directed into the guttering.
I need to do the same along the full length and am wondering if some flashing tape would do the job. i.e this. Or is there a more suitable product?

3. Water sits on the base and seeps inside.
Any rain that hits the walls still runs down and sits on this ledge between the cream and grey blocks. The cream blocks are sat on DPC, but even so we are getting some damp patches along the base of the wall inside.
LdWjY40.jpg

I assume I need to put something on this ledge so water runs off and doesn't sit there. Would a simple mortar edge angled at 45 degrees do the job? Is there something more attractive I could do/use?

Cheers
 
Sponsored Links
Joined
30 Dec 2018
Messages
11,605
Reaction score
1,625
Country
United Kingdom
That looks like it has been a botch, not planned properly. Botching it some more....

That photo looks as if DPC has been pushed up from the gutter, could you do the same along the rest of the gutter? I wouldn't expect the flashing idea to last long unsupported.

I wonder if a series of 25mm wood thick blocks, pushed in between the H girder and those timbers would help the drainage any.
 
Joined
2 Dec 2017
Messages
2,368
Reaction score
444
Country
United Kingdom
as above, the garage and roof construction were not properly planned.
go on utube and see "fix my roof" doing a GRP roof - he's very good and helpful.

things possibly wrong with your garage construction/roof are:
ponding - its never a good idea, and as your calculations suggest there's hardly any falls to the roof.
the use of a small raised "bump" drip trim at the gutter edge of the roof - why create a dam?
the lack of a "drip piece" or "drip batten" above the gutter.
you could use "Flashband" on the drip face to lead the water into the gutter - but it would only be a temporary measure.

was the GRP laid on raw OSB or felt?
are the joists on 400mm centres?

why the ledge at the DPC level is a mystery - your idea of a sand and cement fillet would work for a while.

dont wedge anything up or you might crack the GRP or create other difficulties.
 
Joined
2 Feb 2006
Messages
46,237
Reaction score
3,221
Location
Staffordshire
Country
United Kingdom
Needs a drip forming at the fascia run-off detail and a plinth brick laying around the edge. The plinth could have a tile crease drip along with some sort of cladding or rendering below.

Poorly designed/thought out build.(n)
 
Sponsored Links
Joined
29 Sep 2016
Messages
11
Reaction score
0
Country
United Kingdom
Thanks for the replies everyone.(y)

I wonder if a series of 25mm wood thick blocks, pushed in between the H girder and those timbers would help the drainage any.

There are a couple of blocks under some of the timbers on one side (opposite side to the down pipe) and looking at the ponding on the top it seems they might help.

as above, the garage and roof construction were not properly planned.
go on utube and see "fix my roof" doing a GRP roof - he's very good and helpful.

things possibly wrong with your garage construction/roof are:
ponding - its never a good idea, and as your calculations suggest there's hardly any falls to the roof.
the use of a small raised "bump" drip trim at the gutter edge of the roof - why create a dam?
the lack of a "drip piece" or "drip batten" above the gutter.
you could use "Flashband" on the drip face to lead the water into the gutter - but it would only be a temporary measure.

was the GRP laid on raw OSB or felt?
are the joists on 400mm centres?

why the ledge at the DPC level is a mystery - your idea of a sand and cement fillet would work for a while.

dont wedge anything up or you might crack the GRP or create other difficulties.


Thanks, that "fixmyroof" video series was very useful. Seems the mistakes made were pretty stupid and very easy to do properly first time around. Worst case, I'm pretty sure I could rip it all off and do a better job myself now.

I think GRP was laid straight onto OSB. No expansion gaps that I can see, don't think it was T&G either as I spotted a few bits where resin has dripped through.
And yes, roughly 400mm centres - is that correct or yet another mistake?:LOL:

Needs a drip forming at the fascia run-off detail and a plinth brick laying around the edge. The plinth could have a tile crease drip along with some sort of cladding or rendering below.

Poorly designed/thought out build.(n)
Thanks, so something like this and then rendered below?
https://www.travisperkins.co.uk/spe...ape-brick-plinth-stretcher-pl3-2/p/9000155444

On a side note, in terms of cladding, we did think long term of cladding it in wood, to match another garden building we have. But from reading permitted development specs the garage needs to be constructed from substantially non-combustible materials as it is right on the boundary next to other garages. So would that not be possible under permitted development?

Thanks again all
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Top