Felt flat roof replaced with EPDM - big ponding

dellboy102

Hi All

Was hoping for some advice, I had a felt roof on a outbuilding with a lot of ponding in the middle, this eventually caused the roof to sag in the middle (because of the weight of the water) and subsequent cracking of ceiling (because of the sag) and a leak.

I went on the competentroofer website and got a few quotes to replace existing felt roof with EPDM and add a pitch so the water runs off correctly, I made it clear I want a pitch to prevent further ponding, roofer confirmed they will remove old boards, add firrings and new boards etc to correct the pitch, they've now completed the job and I've still got the same big pond in the middle of the roof despite them trying to add the pitch, I'm guessing they did not properly correct for the sagging.

My concern is the sagging will only get worse because of the amount of water being collected, also with a new roof I dont think its reasonable to have that much water collecting, especially since I made them aware of the issue and paid for firrings, new boards etc as per their advice.

I've already given the company my feedback and am waiting for the response as i'm not happy to pay the full price i've been invoiced and the end result, looking online I do not see a easy way to correct this once the job has been completed but I could be wrong.

Would appreciate any advice on how to deal with this situation, especially if others have been in similiar predicaments.

Thanks

PhilE

If in your contract with them they have stated that they will correct the pitch so that there is no more ponding, which is feasible, then they have not done what you paid then to do.

Write a letter stating your concerns, requesting that they complete the job.

Is it a limited company?

TheCyclingProgrammer

Do you know what they did to correct the roof pitch? I don't see how it could still be ponding if they did what they said they would do. I would do what PhilE suggested - get them back to look at the problem. See what they say.

As always with these things, post some photos, I'm sure there are a few roofers/builders on here, they may be able to give you a better appraisal if there is something to look at.

docmatt

The only way it’s still ponding is because they either haven’t used firrings or the roof is that big they’ve used firrings but the overall roof has a mother of a dip dead centre.
Bear in mind that Standing water shows up loads on an epdm roof.
Do you think firrings have been used but there is still a slight dip but it looks worse than it is?

Can you post some pics? The roof won’t leak so don’t worry.

Did you see them take the old boards off? Would have been quite a mess.

I know it’s too late now but avoid any of these competent roofer, checkatrade, my builder etc sites. Always go on recommendation or contact the NFRC for a roofer who covers your area.

Look forward to the pics.

Furts

Much like docmatt is saying, but put differently. Did you specify what fall you wanted and how it was to be achieved? The fall could be correct, and for this you will need the manufacturers recommendations.

Rule of thumb would be around 1:40, but have you done a survey to establish what you have?

If you have a dicky construction then the fall could be adequate but the underlying structure sagging so you end up with ponding.

teneighty

I would suggest that the roofing contractor is liable. If they were specifically instructed to correct the ponding then they should have checked the roof for level and falls. There is no need for a layman customer to have to do a survey of their roof and specify the required fall, that is why they employ "competent" tradesmen.

It sounds like they simply put firring pieces on the roof without checking that the roof joists sagged in the middle.

The only way to correct this is to fix the sagging roof joists (if that is the problem) or strip the roof off and replace the firring pieces and deck with larger firring pieces to overcome the sag.

dellboy102

He said for the size of the building the wooden joist or support is not strong enough hence why it sagged, he's offered to use Acrow prop to lift in the middle and install a new beam for no cost, but no guarentees whether it will fix but hopefully it should help.

I'm thinking to let him try this and take it from there, his explanation was even if they packed the areas which had sagged it would not have helped as the insulation panels would have sunk into the packing, not sure that is right but at this stage not much else I can do apart from let him try and resolve with this suggestion above.

Also spoke to another roofer who reckons EPDM is pretty tough so shouldnt leak or bow any further even in its current state.

I guess my frustration is as I've gone for a complete re-roof (reboarding, new firrings etc) I thought this could have been fixed at that stage, I'm not an expert so not sure what to make of his explanation.

I'll probably get him to try his suggestion and take it from there, any thoughts on this?

docmatt

Ok, the beam thing will help as long as it doesn’t get in the way inside. Then you’ll have just a bit of pooling. That’s a flexR epdm lsfr membrane he’s used, a tad thicker than the firestone stuff so it’s good stuff.

He just needs to finish the gutter trim, he’s used 2x 2.5 metre lengths and the width looks about 5.3m ish. Just a tiny bit needed for the end.

Like your mate says it will never leak through the membrane no matter how much standing water is on it.

dellboy102

docmatt wrote: »

Ok, the beam thing will help as long as it doesn’t get in the way inside. Then you’ll have just a bit of pooling. That’s a flexR epdm lsfr membrane he’s used, a tad thicker than the firestone stuff so it’s good stuff.

He just needs to finish the gutter trim, he’s used 2x 2.5 metre lengths and the width looks about 5.3m ish. Just a tiny bit needed for the end.

Like your mate says it will never leak through the membrane no matter how much standing water is on it.

Thanks for the info, good to hear the membrane is decent!

I was more concerned whether I'll get further sagging due to the weight of the water that will pool, the sagging (and subsequent leak) on original felt roof is what caused the plasterboard to crack on the ceiling inside the building.

The gutter they did finish off so that part is fine at least

Furts

Somewhat worrying. What you are being told is the rafters are under sized, and unsuitable for your roof. Considering there is no weight to your roof they must be very flimsy for this to be so. I say this because concrete roof tiles are heavy, but your original felt was not so. Even more worrying the photo looks like there is only one rafter taking all the roof weight. This is so improbable that i will write this off as impossible, but it does look like that could be so.

Now consider characteristics of timber. Your rafters have sagged and will have formed a natural bowed shape. This cannot be corrected by jacking the timber - you will not remove the bow. Inserting a new correctly sized rafter could form a cure, all the more so if you only have one rafter.

fezster

dellboy102 wrote: »

He said for the size of the building the wooden joist or support is not strong enough hence why it sagged, he's offered to use Acrow prop to lift in the middle and install a new beam for no cost, but no guarentees whether it will fix but hopefully it should help.

I went on the competentroofer website and got a few quotes to replace existing felt roof with EPDM and add a pitch so the water runs off correctly, I made it clear I want a pitch to prevent further ponding, roofer confirmed they will remove old boards, add firrings and new boards etc to correct the pitch, they've now completed the job and I've still got the same big pond in the middle of the roof despite them trying to add the pitch, I'm guessing they did not properly correct for the sagging.

Seems pretty straightforward. You *specifically* asked for something to be fixed, you instructed a professional who is competent in his field to complete the job, they confirmed they would ......... and they haven't.

If you had gone to them and told them you want a new roof with x, y and z to be done, they may have an argument to justify not fixing the problem - but even then, being a competent person, they should advise you otherwise. Your case is clear cut because you asked for something to be fixed and it hasn't.