Double garage flat roof repairs

pjmallinson · 29 Nov 2009

I have a double garage about 5x2.7m in need of repair. I'm keen to avoid a complete reroof if possible so plan to redo about half which will more than cover all of the failed areas. I want to do a sound and reasonably long lasting job but as economically as possible. I need to strip the deck off (rather dodgey looking chip or fibre board) and intend to re-deck with OSB 3 (can get 18mm sheets from Wickes I notice at about £15 each if buy 10). Joists are all sound and at standard 610/2ft centres. The question is whether A) to attempt a conventional 'built up' covering using hot air or torched (will need to hire equipment) or B) use a cold applied adhesive system or C) a self adhesive system or D) go for single membrane and adhesive? There seem to be negative attitudes toward the latter.
I'd much appreciate some expert advice and suggestiions as to specific felts, moisture layers, caps, adhesives etc to use.
Thanks in advance . PeterM

Deluks · 1 Dec 2009

Consider the bitumen backed osb as wickes seem to be doing them again.

A) do you have the skills to carry out this work?
B) + C) Cost vs hassle. One's messy and cheaper, the other is clean but quick and expensive. In any case, don't skimp on the felt quality.
D) single ply EPDM aka rubber roof is a good solution.

There's also roofing shingles to consider, fibre cement sheets (like the old asbestos type but safe) Batten and tile if it can take the weight, corrugated bitumen sheets...... so much choice, you gets what you pays for generally.

pjmallinson · 1 Dec 2009

Deluks";p="1425999 said:
Consider the bitumen backed osb as wickes seem to be doing them again.

A) do you have the skills to carry out this work?
B) + C) Cost vs hassle. One's messy and cheaper, the other is clean but quick and expensive. In any case, don't skimp on the felt quality.
D) single ply EPDM aka rubber roof is a good solution.

Many thanks for your response Deluks. Bitumin backed OSB sounds good. I presume it makes for better adhesion of any of the felt options?
Yes I do have plenty of building skills and experience (40years!) but strangely not with flat roofs. The roof has only about 1:60 slope so I am inclined to stick with some kind of built up system or maybe EPDM.
Although I will be able to keep the entire roof dry during the process I'm keen to choose the quickest and easiest solution as I don't have the luxury of postponing it till the good weather of spring. I need to do it now. Would you suggest avoiding any torch on system if you haven't done it before, REGARDLESS of general high levels of expertise, skill and experience? Maybe it is a particular rocket science?
If it should be a non torched sytem would you recommend cold applied adhesive over any 'self adhesive' types?
In contemplating EPDM the single membrane is appealling but is it any problem getting it 100% adhered? I assume it is important to.
I'd be glad of your thoughts. Thanks. PeterM

isettaman · 1 Dec 2009

Peter

I have personal experience with EPDM.

I did have a bit of trouble getting it onto the roof to start with as my garage is 6 x 6.5m - very heavy! Fortunately I have a tractor with a front bucket so I put it up with that.

The theory is, with the stuff I used, that you use water based adhesive spread with a emulsion roller.
The membrane is spread over the garage with a suitable overhang on all sides.
You then fold half of it back and spread the adhesive on the roof timber. Unfold the membrane back, using a wide soft broom to smooth out any air pockets, repeat the process with the other side.
With the size you will be using this should not present a problem.

It usually comes with edge and gutter trims to finish it off.

Have a go!

Dave

pjmallinson · 2 Dec 2009

isettaman";p="1426296 said:
Peter

I have personal experience with EPDM....

Thanks for that encouraging info Isettaman. Have looked into EPDM a bit more seriously as a result. There seems to be a thickness choice to be made; either 1.14mm or 1.5. The thicker is 20% dearer. Is it better or is it unnecessary overkill for a garage? Perhaps it's designed for a 5000 sq metre warehouse roof? Obviously heavier too.

By the way does 'Isettaman' indicate any connection with Isettas? I have fond memories of one in the 1960's! It was a magical machine.

cumbrianroofer · 2 Dec 2009

my advice is get aroofer to do it torch on felt underlay follwed by torch on glass fibre felt the size of your roof a good roofer could have the boards of new ones on and underlayed in about a day followed by another day to do the top layer to keep costs down ask for labour only price then you can get materials yourself and theres no hidden costs definatly wouldnt try doing yourself if you havnt done it before it is pretty dificult give me slates or tiles any day

flat roof cumbria

cumbrianroofer
2 Dec 2009
2

isettaman · 2 Dec 2009

"By the way does 'Isettaman' indicate any connection with Isettas? I have fond memories of one in the 1960's! It was a magical machine."

I used the 1.14mm stuff which I found perfectly suitable for the job.

I had an Isetta as a teenager, cost me £30!

I also bought one a few years ago and fully restored it but sadly it had to go last year as I rarely used it and I needed the space.

BTW total cost for my 6 x 6.5m2 roof with trims was £620

Dave

pjmallinson · 3 Dec 2009

cumbrianroofer";p="1427591 said:
my advice is get aroofer to do it..

Thanks for that slightly depressing advice. Trouble is I started off getting a quote for a traditional Built Up job which was £2.5k+ for 5.2x6.4 roof and unfortunately that's way beyond my means. As I mentioned in an earlier post I do have a lot of building and engineering experience and skill, about as far away as you can get from a DIYer. Do you still say it's a definite no no? Perhaps you are a professional roofer? Thanks, PeterM

Deluks · 3 Dec 2009

If you think you can do it, then you probably can.

htgeng · 3 Dec 2009

Deluks said:
If you think you can do it, then you probably can.

With an EDPM sheet how to do you neatly fold/overlap on the corners? the crease at the corner is surely going to be a weak point. If its just a garage then why not build up more of a slope so water doesnt pond. Then felt or if you can wait till it gets warmer then fibreglass.

cumbrianroofer · 3 Dec 2009

sry my friend didnt mean to be so depressing but putting on the top layer is pretty difficult but you could also take of old roof yourself reboard no problems at all and poosibly even underlay it im a roofer of 20 year and as i said a good roofer should bedone in 2 days so if you bought materials your looking to pay no more than 6-800 pounds to be honest even less if you did the prep work

isettaman · 3 Dec 2009

The answer to the edge problem is simple, you fold it over the edge as you would wrapping a parcel - remember it isn't that thick but it is strong - and then secure it with the edge trim provided.

Dave

pjmallinson · 4 Dec 2009

cumbrianroofer";p="1428915 said:
sry my friend didnt mean to be so depressing...

Thanks Cumbrianroofer. No problem. And your suggestion to do all the 'easy' work by getting the deck on then call in the professionals to do the felting sounds like an excellent solution. I shall go forth and investigate.

The cheapest option for boards seems to be Wickes 18mm OSB3 at about £15 a sheet. Is this adequate and is it the cheapest 'approved' option (way cheaper than Travis Perkins where I have a trade account!). Obviously I shall need to ensure the deck is dead flat and with no gaps etc. Is it better to use a T&G type board or not necessary? And which underlay do you recomend? Sorry about all the questions.

Thanks again, Peter

cumbrianroofer · 5 Dec 2009

wickes 18mm ply would be suffecient mate and the underlay can be bought at travis perkins or atkinsons build center costs about £35 for a 16mx1m roll approx 14m2 just ask for flat roofing underlay you can practice using torch putting it on and if you feel comfortable tackle thetop layer just make sure the boards are butted tight and you will have no problems

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Double garage flat roof repairs

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