On Friday, 14 September 2018 22:05:16 UTC+1, JimK wrote:

Be interested in updates on outcome of this &, essentially, who
ends up paying/ giving in...

The builder visited today€¦

He was actually very good about the situation and quickly held his hands up once hed checked and measured the firring strips himself. Whilst the finished roof does drain, and in his opinion wouldnt prematurely leak, he acknowledged that its fall was below-spec it was my prerogative to be concerned and to expect a remedy. To this end we came up with a few options; the choice of which is entirely mine and he will pick up the bill:


1. Leave As-Is €“ He would give me a guarantee in writing that should the roof fail in the next x years (to be agreed) he would repair/replace and make good any consequential damage. To give me greater confidence he could also get the roofer to add another layer of the liquid membrane to the existing. He would also refund the initial £1000 roofer cost.

2. Remove and Rebuild €“ Rip up the entire roof deck (membrane and trims, top boards, insulation, bottom boards and firring strips) and replace (likely with bought firring strips this time €“ he had no idea they were available off-the-shelf hence why he always cut his own, normally without making a mistake with the measurements!)

3. Overboard and Recoat €“ Keep the old roof in place (bar the trims), add a new layer of OSB3 on top of suitable firring strips to give the correct fall and put a new waterproof coating on top.

I am not comfortable with option 1 as whilst I trust his word regarding the guarantee (we live in a small town, him and his son just down the road from me; theres nowhere to hide!) my preference here is to avoid a leak in the first place rather than deal with one if/when it happens. Id also like to draw a line under the situation rather than leave things hanging over me/us.

Option 2 was my initial preference as this gets me back to the position I was in before the mistake happened and therefore not be considered a €˜bodge in any way. However, his initial thoughts were that it could cause more problems than it solves. We didnt get into too much detail about it but his concerns were about the destruction required as with all the fixings now hidden thered likely be a lot of €˜coercion of materials and could lead to damaging other components. Might be worth pushing further though, particularly as I'd be more than happy to help with the removal side.

Option 3 sounds like a viable option as not only does it give me the opportunity for a new waterproof coating (I am leaning more towards a single-sheet EPDM membrane rather than another liquid coating - ever since it went on my confidence in it has not been the greatest as it is far from conventional and so seemingly not much information about it) but the extra board/membrane layer may also provide an additional noise and solar barrier? I certainly wouldnt ever expect a leak through two surfaces either, at least not down into the living space! I am wondering about potential downsides though... It would add ~50mm to the roof height at the rear wall abutment which would eat into the 150mm lead flashing and the roof lantern upstand would require extra timber on top to increase its standoff height. Could there be a risk of interstitial condensation with this extra layer or would it be okay given it is on the cold side of the insulation? Should the gaps between the firring strips be filled with anything? (Note the strips will likely be 40mm to zero over a 3m span so not much volume there).

As before I would be grateful for your thoughts. The builder is being completely open and supportive of the situation and keen to make sure I am happy with the outcome €“ I just need to work out what the best outcome should be!