PUDDLES (not my cat) ON A FLAT ROOF

D

DAJ

I've recently replaced an entire flat roof. The existing roof was fairly sound but, as a consequence of an extension being erected part on the flat roof, the direction of fall had to be changed. In addition a sky lite had to be removed.

I first removed all existing felt (not torched on) that had been there for around 20 years. I then removed the planks/decking afterwhich I removed the existing furrings from the joists.

I then fixed replacement furrings to the joists giving a fall along their lengths from each end to a "trough". This also had a fall in a different direction to take the rain water away to a gutter.

I then screwed down 15 x 2400mm x 1200mm x 18mm plywood sheets to the furrings. I sealed all the joints with silicone. I then felted the entire roof. I layed several layers of felt in the trough to help the fall, first layer butt jointed then overlapped.

My intention was to tank the trough "just in case". But first, I thought I'd test the fall with a hose. This I done and was very pleased with the way the water drained from the roof. HOWEVER (I hate those howevers!), I now have a puddle obviously at a low point. My guess is that I hadn't accounted for the possibility that the joists may have had a slight sag in them or the furrings hadn't been cut (by the timber mills) exactly.

Anyway, I can guess away and wonder - the point is, has anyone any suggestions as to how the problem may be resolved. I was thinking of cutting more felt in the shape of a triangle to encourage the water to go where I want it to.

Any help would be helpful (but please , no, should'ves). THANKS!
 
Sponsored Links
You will definitley have trouble with the roof in the future as felt will not stick to silicone,infact silicone acts in a negative way to bitumin(try sticking silicone to piece of flet,leave for a week and view the results,it also says this on most silicone tubes).What will happen is where ever the silicone is you will get ridges/wrinkles and in time these will fracture,admittingly it will take several years with hp t/o but it will happen,sorry. :confused: as for the standing water-if it only a little and it evaporates in a short time its not a big deal(rule of thumb is if its gone in 48hours your ok) but if its a big puddle it needs sorting.You can build it up with t/o felt but unless your carfull you could just shift it from one place to another.A good way is to pour hot bitumin where the puddle is then felt over but this is not practical if you not a roofer=need a boiler,burner,pan/pouring can and its a dangorous job if no exp.It would not cost alot for a roofer to pour bitumin in the hole,you could then felt over yourself?
 
  • Thanks
Reactions: DAJ
You will definitley have trouble with the roof in the future as felt will not stick to silicone,infact silicone acts in a negative way to bitumin(try sticking silicone to piece of flet,leave for a week and view the results,it also says this on most silicone tubes).What will happen is where ever the silicone is you will get ridges/wrinkles and in time these will fracture,admittingly it will take several years with hp t/o but it will happen,sorry. :confused: as for the standing water-if it only a little and it evaporates in a short time its not a big deal(rule of thumb is if its gone in 48hours your ok) but if its a big puddle it needs sorting.You can build it up with t/o felt but unless your carfull you could just shift it from one place to another.A good way is to pour hot bitumin where the puddle is then felt over but this is not practical if you not a roofer=need a boiler,burner,pan/pouring can and its a dangorous job if no exp.It would not cost alot for a roofer to pour bitumin in the hole,you could then felt over yourself?

MISTAKE! apparently, after looking closely, it wasn't a silicone sealer, it was a black sealer for guttering - NOT silicone (phew).

I like the idea of bitumin and felt and a good point about a roofer doing the main work then me just felting. I've heard some horror stories about novices playing about with hot bitumin.

I'd like to say though, that i used ordinary heavy duty felt and not torch-on. I used heavy duty adhesive (13 x 5 ltr. cans) to lay the felt as I feared fire using a torch on felt and bone dry ply in the hot sun! Like I said, I've heard some horror stories.

I was quoted £2,000 by a roofer for the whole job and i managed to carry out the work for less than £600. Admitedly, i now have puddles but whose to say the roofer wouldn't have (I know he would have to put it right, just a point!).

Is there any self-leveling compoud, like screed, that can be used?

Anyway, thanks for the advice.
 

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

 
Sponsored Links
Back
Top