Flat roof advice re some pooling and laying decking

[silver50]

Hi folks

I've just had a small roof terrace re felted.

Unfortunately the new felt is pooling a bit but not dreadfully badly. Only a couple of 3'x3' areas. I'm not going to fret about it too much but I occasionally see some pebble type surface on top of felt. What is this and should I buy some to put on the areas that are pooling? I assume this helps stop too much water lying/collecting?

Any ideas on what to support joists on for the decking are welcome. I might just go for the adjustable plastic supports though.

 

[Alastairreid]

The chippings on the surface of flat roofs is to protect the felt from the sun and uv light not to stop pooling.
Standing water within reason wont do any harm.

 

[silver50]

Thanks

While accepting it might not be a big problem I can see today we would be talking a bit of time for the pools to dry, probably a good day or two. Not sure why it's pooling like it is but there is obviously a bevel I didn't expect.

Could I try to screed over the areas with some bitumous gloop??!! I was thinking maybe a tin of something with a thick consistency perhaps for glueing felt down. I'd drag a straight edge over the area to try and fill where the puddles form. The decking will then be above this

 

[Alastairreid]

Wont do any harm but maybe not adhere to the mineral surface on your felt unless you primed it.

 

[silver50]

Its not actually mineral topped, its Plana P 4mm non mineral

 

[Alastairreid]

Ah sorry was going by the pic you posted.

 

[silver50]

I was going to get some aluminium silver paint from a roofing supplies company tomorrow. I can ask them if they've any ideas for something to pour to try and level off the bits that pool. It seems not a bad plan to try and stop water sitting if poss. Certainly lessening it would be good

 

[John D v2.0]

They shouldn't really have refelted a roof where the structure was not satisfactory. Nominal fall should be 1 in 40 to allow adequate drainage. Ponding must be avoided as standing water will ruin flat roof coverings.

 

[silver50]

They shouldn't really have refelted a roof where the structure was not satisfactory. Nominal fall should be 1 in 40 to allow adequate drainage. Ponding must be avoided as standing water will ruin flat roof coverings.

I don't disagree. However in fairness to the roofer who did this the existing top level was well above the plywood base (the felt-membrane-tile adhesive-top tiiles/small slabs) and it wasn't pooling particularly badly. The ply looked level enough when he felted it but it seems it must've been bevelling in a bit. It is a pest but the chance seems likely to be zero that he'd re-do it all and I'd rather aviod that anyway.

Doing my best to try and stop water collecting too much (especially as two smallish areas) seems the best idea. Hopefully worthwhile while I have the chance and better than doing nothing.

 

[John D v2.0]

I'm sure any good roofer would know that a spirit level and straight edge are far more appropriate than using eye to check falls and sagging. He should be doing that to avoid causing himself expensive remedial work. On the other hand, he could just refuse to do it properly and get the customer to pay anyway.

 

[silver50]

I'm sure any good roofer would know that a spirit level and straight edge are far more appropriate than using eye to check falls and sagging. He should be doing that to avoid causing himself expensive remedial work. On the other hand, he could just refuse to do it properly and get the customer to pay anyway.

It's not been impressive.

Not actually paid it all yet..

Also not sure how that's going to pan out..

 

[John D v2.0]

It's very difficult, we had the same issues with substandard work with our builder. Fortunately we had an architect and SE on our side who could tell the builder if something was wrong and resulted in expensive remedial work at no extra cost to us. As far as the builder was concerned the main thing was it looked about right, so I was glad to have an expert on side. But on a smaller piece of work the cost of someone to specify and supervise things might be more than the work cost!

 

[silver50]

Yes you're right. I'm generally not short on some level of building/DIY knowledge so I'm someone that can see a right way and wrong way clearly but as you say the problem is putting it over and it's chances of attaining anything other than an argument.

Thats why I'm just going to do my best to sort it out a bit. Bought trowel on bitumen today which seems a fair consistency to screed over the pooling areas a bit. Limiting the bad standing water should make a big difference in time it takes to dry off after rain. Some standing water is often inevitable so hopefully it'll last ok. Today I put some black CT-1 on the felt seams. This is a fantastic product and it should really help stop any chance of water creeping under seams as time goes by.

It's going to be interesting to see if roofer re appears on me.

 

[John D v2.0]

Good, hope it goes well!

 

[chappers]

some pooling isn't inevitable, there shouldn't be any. there should be enough fall to overcome minor deviations in the deck surface.