Roof dipping / concrete tiles (used to be slate)

[skhudy]

I have a roof at the back of the house (separate from the main house roof). Its a Terrace house with an L shape if that makes sense.

+++++
+++++
+++++
+++++
+++
+++
+++
+++

Main House is Slate, the roof at the back concrete. Its clear at some time in the past the slate at the back has been replaced with concrete tiles.

The roof at the rear is bowing towards the middle, clearly as it was not designed for the weight of the tiles.

Looking in the roof void the purlin bows. A couple of king posts have been added on the 4x2 roof floor (or room ceiling) to the purlin.

I've had someone in and they will be getting a quote to me to strip the roof and renew the rafters. They did suggest before looking it might be possible to put in a series of king posts but after looking they thought it was bowed too much for this.

Are there any other creative solutions which should be considered, or is there no choice other than renewing the roof? I did wonder if it might be possible to work through the rafters one by one and jacking them up and putting in the suggested king posts? or is the problem once the rafters start bowing they cant be straighten?

 

[catlad]

I have straitened a lot of old roofs.
Ditch the tiles in the skip and with the weight
off you should be will be able to prise the rafters
off the purlin which can be packed up with folded bits of lead, but if the purlin is badly bent then you can bolt a
straight length of timber to the purlin.
You will need to use a string line.

 

[skhudy]

The builder + roofer (2 of them) are in tomorrow, I've come back and seen the new tiles have been dropped off. The new ones are double roman concrete roof tiles.. I thought the original conversation I had with builder / roofer was the weight of the concrete tiles was causing roof to dip, so he's going to rip off the old concrete tiles, and put on new concrete ones - is that o.k? With it he is adding king posts to the rafters, is this an accepted method to renew a dipping roof?

 

[catlad]

It doesn't make any sense, why if you are going to strip the roof and put on some new material would you
not use slate.

 

[Alastairreid]

If the roof is strengthened properly to accommodate the weight...no problem.

 

[skhudy]

Roof is being strengthened. He explained to me the new rafters (old ones very bowed) and strengthening to purlin and king post etc. Maybe a misunderstanding on my part, I think I assumed lighter tiles were going on (seemed logical to me!). Problem is I was quoted for several jobs, but they were only split into labour and materials, not a breakdown on the jobs and materials to be used. As it goes, the roofer had a bad back, it was a bit icy and the job has been put back till next weekend. Lesson learnt for me, get the full breakdown of the job / materials in future!

 

[catlad]

If your annex is original to the house and it originally had
slates on like the rest of your house I find it bizarre that
anything other than slate would be used considering aesthetics and the issues you have structurally.

 

[datarebal]

May as well put the old concrete tiles back on?
Personally I would have straightened things up and slated it like it was meant to be.

Roofers, builders.. bad back.. A bit icey.. umm

 

[skhudy]

Many Thanks all. I think the lesson learnt for me is get the exact job details prior to work starting. I made an assumption when getting the quote, and talking how the tiles were too heavy for the original structure, that a lighter tile was going on (although sure I said about getting rid of the concrete tiles). The other is not to get work done by someone connected to some you know or works for you - just makes things awkward. They are genuine tradesman, the roofer works for a big local company, but as with anything in the building trade there can be several ways to skin a cat, the way one person does it may not be how others (or I) might think it should be done!