Roofing under a tent

[Tony K]

Hi

My SB is a 100m2 flat roof bungalow for which I intend to use grp. I've tried to program work so as to avoid roofing in the winter but the mortgage company have other ideas it seems, leading me to consider hiring a marquee or tent to bridge over the building and keep rain off whilst roofing. 

 

The building is an L shape, and no part of it is wider than 5.5m.

 

Has anyone hired a gazebo or marquee to sit over a roofing project? Any pros and cons based on experience? 

 

Ta

Edited September 20, 2020 by Tony K

[Russell griffiths]

Get a scaffolding co to stick a scaffolding platform to get access to a point from which you want to work, then a tarpaulin roof over the rest of the structure. 

Will be the best money you spend, 

[Tony K]

3 minutes ago, Russell griffiths said:

Get a scaffolding co to stick a scaffolding platform to get access to a point from which you want to work, then a tarpaulin roof over the rest of the structure. 

Will be the best money you spend, 

 

Sounds more expensive than hiring a tent?

[Nickfromwales]

19 minutes ago, Tony K said:

 

Sounds more expensive than hiring a tent?

A ‘tent’ of that size will likely need one or two poles to ground ( which would be on top of your roof ). 
Scaff with poly tent or tarp would be your only choices afaic. A tarp will cave in and fail unless supported by horizontal poles, lots of them, and they’d need supporting so you’re back to scaff. 
Accept, move on, conquer, and get to the next bit  

[nod]

2 hours ago, Russell griffiths said:

Get a scaffolding co to stick a scaffolding platform to get access to a point from which you want to work, then a tarpaulin roof over the rest of the structure. 

Will be the best money you spend, 

A neighbour at our last house did exactly that when building there very large two story extension 

Built the lot while completely covered Even blew hot air in to carryon laying bricks 

As Rus has already  stated It will be the best money you have spent 

0 chance of the GRP going tits up 

 

[joe90]

Many moons ago I was contemplating building in straw bale and looked into buying scaffolding including a corrugated iron roof so I could complete in the dry, I was informed I would get most of my money back when selling it as long as I oiled the couplers so don’t discount it.

[Tony K]

I suppose the other angle on this is: how weather sensitive is grp in reality?

 

I appreciate that the instruction videos and manufacturers details specify dryness, but with the changeable British weather plenty of folk must get caught out by unforcasted rain. How problematic is that when it happens? 

[joe90]

11 hours ago, Tony K said:

How problematic is that when it happens? 

very!!!!, any damp whatsoever will spoil it (not sure why and how but @SteamyTea will be along in a mo to explain).

[SteamyTea]

34 minutes ago, joe90 said:

to explain

Because the resin needs an oxidising agent to link the polyester chains together.

So it tries to get the oxygen out of the water, but it cannot break the strong H₂O bond, so the water just gets dispersed in the free stryrene, which is carbon and hydrogen, and does not need anymore hydrogen.

 

Or

 

It just makes a sticky mess.

Edited September 21, 2020 by SteamyTea

[Tony K]

2 minutes ago, SteamyTea said:

Because the resin needs an oxidising agent to link the polyester chains together.

So it tries to get the oxygen out of the water, but it cannot break the strong H₂O bond, so the water just gets dispersed in the free stryrene, which is carbon and hydrogen, so does not need anymore hydrogen.

 

Or

 

It just makes a sticky mess.

 

Thanks. I completely understand the second bit! 

 

There seems to be some advice on a few grp manufacturers websites that if it starts to rain you should stop work and pull a rain cover over the area. It doesn't say that rain is anything other than a bad thing, but it also doesn't describe rain as fatal. 

 

I can understand that full on rain will be a problem, and that the surface should be dry before you get going. I would of course check the forecast before getting started, but the website advice suggests that which instinct suggests - it can't be the case that every grp roof is made only in summer or under a cover? Are roofers just risking it I wonder? If so how great is the risk? I understand that it cures pretty quickly, so am I right in thinking that all I need is one clear day? 

 

Thanks 

 

 

[SteamyTea]

1 hour ago, Tony K said:

Are roofers just risking it I wonder

Basically yes. Damp boards can stop the resin curing where it makes contact, even if the outer is hard.

This can lead to premature failure and a prolonged smell of styrene.

 

Strong sunlight and high, or very low temperature can also cause problems.

 

As I keep saying, if done right you can't get better, if done wrong, it gives it a bad reputation.

[joe90]

I have come across several GRP roofs that have failed after the fact and due to moisture either in the air or within the deck. (I didn’t do them ?) As @SteamyTea says, bullet proof if done well and VERY dry. I have done a few and only when absolutely no rain is forecast and decking just put down to guarantee it holds no moisture.

Edited September 21, 2020 by joe90

[Tony K]

1 hour ago, SteamyTea said:

Basically yes. Damp boards can stop the resin curing where it makes contact, even if the outer is hard.

This can lead to premature failure and a prolonged smell of styrene.

 

Strong sunlight and high, or very low temperature can also cause problems.

 

As I keep saying, if done right you can't get better, if done wrong, it gives it a bad reputation.

 

59 minutes ago, joe90 said:

I have come across several GRP roofs that have failed after the fact and due to moisture either in the air or within the deck. (I didn’t do them ?) As @SteamyTea says, bullet proof if done well and VERY dry. I have done a few and only when absolutely no rain is forecast and decking just put down to guarantee it holds no moisture.

 

Thanks chaps, good advice and understood.

 

So my safest way is some sort of cover (scaffold being the best, and perhaps only viable option). If I were to decide to risk it without a cover, its not just a case of it not raining on the day. I need to ensure that the deck is thoroughly dry before I start. 

 

A feature of my design is that the roof is very simple to build. This is so that if, by that stage of the project,  I need to save money I can do so by building it myself (with family roped in). This will take longer than if a roofer did it of course, and also mean that the deck is out under the weather for longer.

 

I suppose I could build the deck, insert the grp edging forms and upstands, then if any of it gets wet place a ventilated polythene sheet over it all to dry out thoroughly whilst I wait for a couple of clear days to do the resin and topcoat?

[joe90]

Or, you could cut the roofing decking Parts and pre treat them with GRP, you then only have to do the joins, I have never done this but read about it.

[SteamyTea]

36 minutes ago, joe90 said:

pre treat them with GRP

How I would do it.

 

[Tony K]

44 minutes ago, joe90 said:

Or, you could cut the roofing decking Parts and pre treat them with GRP, you then only have to do the joins, I have never done this but read about it.

 

That's interesting. If I am using 18mm t&g osb would I just literally apply a sheet of matting to each board, let them all go off, then fit them in place? 

 

Would I be against the clock once I begin applying the matting to the boards? I understood that it was better to get the topcoat on within a short time of the matting sheets?

[SteamyTea]

12 minutes ago, Tony K said:

 

That's interesting. If I am using 18mm t&g osb would I just literally apply a sheet of matting to each board, let them all go off, then fit them in place? 

 

Would I be against the clock once I begin applying the matting to the boards? I understood that it was better to get the topcoat on within a short time of the matting sheets?

Put at least 2 layers of 450gsm CSM on. You can leave it at 1 layer around the edges. Wait till fully hardened, lightly sand down. Get all the dust off, then apply topcoat, except for the edges where the joints will be.

Then fit.

Then lay 2 or 3 layers for your joints. The thicker the better as this will be 'resin rich'. Then, once fully cured, lightly sand, clean and apply topcoat.

The topcoat will have a wax additive in it. So don't expect the normal resin to bind to it successfully.

 

Also. By prelaying up the sheets you get good practice on using the resin.

[Tony K]

5 minutes ago, SteamyTea said:

Put at least 2 layers of 450gsm CSM on. You can leave it at 1 layer around the edges. Wait till fully hardened, lightly sand down. Get all the dust off, then apply topcoat, except for the edges where the joints will be.

Then fit.

Then lay 2 or 3 layers for your joints. The thicker the better as this will be 'resin rich'. Then, once fully cured, lightly sand, clean and apply topcoat.

The topcoat will have a wax additive in it. So don't expect the normal resin to bind to it successfully.

 

Also. By prelaying up the sheets you get good practice on using the resin.

 

Thanks.

So even the topcoat can be done in stages? Would it not be stronger if done in one continuous operation?

 

Don't suppose there are any good youtube videos around showing this technique? There are quite a few very useful ones showing the normal method and I would feel confident following them, but you're talking about next-level stuff!

 

 

[SteamyTea]

48 minutes ago, Tony K said:

So even the topcoat can be done in stages?

Yes, just make sure it is sanded to get a mechanical lock.

 

I don't know of any videos.  Could make one if you were closer.

[Tony K]

38 minutes ago, SteamyTea said:

I don't know of any videos.  Could make one if you were closer.

 

I was going to say that it sounds like I could pack my whole roof up and bring it to you, though I reckon the poor old Toyota Prius might strain a little if asked to carry a 100m2 roof. 

 

I presume the fully treated and coated boards would be screwed into place as per normal, with the screws going through the coating etc, but then being covered over by the subsequent strips?

 

 

[SteamyTea]

30 minutes ago, Tony K said:

 

I presume the fully treated and coated boards would be screwed into place as per normal, with the screws going through the coating etc, but then being covered over by the subsequent strips?

Yes.

Where are you? I could do with a trip up country to see family.

Have you got a large shed?

 

[Tony K]

2 minutes ago, SteamyTea said:

Yes.

Where are you? I could do with a trip up country to see family.

Have you got a large shed?

 

 

I'm in Epsom, Surrey.

I'm not at the roofing stage yet. I have been delayed in getting out of the ground by the remarkably slow and poor performance of the mortgage lender and brokers - thats why I'm asking these questions about the roof; whereas I had planned to do the roofing in the clear, bright days of September, it now looks like a December job.

 

I don't have a large shed. I was just thinking about that. I would need a fairly large, dry place to prepare the boards and let them dry. It might be that I could hire a gazebo for the purpose. 

[SteamyTea]

11 minutes ago, Tony K said:

in Epsom, Surrey

Not far from my family.

 

You need a metre extra at least to work in. A metre all round us best.

Should be able to do 4 boards a day if done individually, as long as you have somewhere to place them on their edge once part cured.

 

[Tony K]

2 minutes ago, SteamyTea said:

Not far from my family.

 

You need a metre extra at least to work in. A metre all round us best.

Should be able to do 4 boards a day if done individually, as long as you have somewhere to place them on their edge once part cured.

 

 

That's useful, thanks. What size board are you thinking of for that sort of rate of productivity?

 

[scottishjohn]

what about fitting a few boards to roof --then just coating in resin including joins  -  do that as weather allows and then come back sand and apply lay-up and top to a section at a time  that way boards are waterproofed ?