Captain's Table

Mark Austen

2021.02.24 - More Workshop Roof Problems

The lovely 20' x 35' workshop we have is suffering problems. The roof capping blew off over the course of the Winter before last and I now have to cover everything that needs to stay dry with tarpaulin. This makes it quite difficult to work in there since the first thing you have to do is clear the tarpaulins. And forget trying to work if it is raining.

Over the last couple of months I've noticed that there are also puddles inside that cannot be the result of rain coming in through the top of the roof where the capping is no more and I found out the reason for this whilst making a cup of tea in the kitchen last week.

You can see the North side of the workshop and roof from the kitchen and I noticed that the lower part of the roof had sagged and in some places quite considerably. I went and had a closer look both outside and inside and I found that the bitumen, corrugated roofing is sagging badly between the lower purlin and the wall and particularly where two adjacent sheets overlap. This forms a "cup" that holds water instead of shedding it and the when it had filled up sufficiently, the water then flows through the overlap and into the workshop.

I used a wooden pole about 3" in diameter to try and push one of the sagging sheets up and to my dismay the pole when right through the sheet indicating that there is a much bigger problem there than I realised.

The obvious thing to do is to replace the roof. This is not a expensive as it might sound. I can easily source 11ft long sheets of galvanised corrugated sheets and the cost of these plus the fixing screws would come to about £600. The problem is that we don't have that much money spare right now and won't do until either Tina gets a job (she was made redundant as a result of the covid-19 pandemic) or the mortgage is paid off in May 2022. The end of the mortgage is the more likely scenario right now.

However, I need the workshop to be usable and dry well before then, so I needed an interim solution to the problem. I decided that lengths of wooden dowel could be used between the wall and the first purlin to give support to the sagging areas and thus remove the water collection area. This proved to be impossible for the simple reason that the maximum diameter that will pass under the upper section of the corrugations is 18mm and wooden dowel that thin would very easily bend. So instead I bought twenty lengths of 15mm aluminium tubing, each one being 1m long and used those to give the support.

Here is a photo of one of the sagging areas. The white seems to be something left behind when the water some through.

This is the concrete floor immediately below the sag and as you can see, it is saturated.

Here is another sagging area and you can see the overlap of the two sheet quite clearly.

Here is the same area but with the tubes now lifting the soft roofing sheets to remove the sag. This was not an easy job. The tube needed to be pushed under the roofing from the inside to the outside for about 40cm (16") so that the upper end of the tube could be pushed up and over the purlin. Then the whole thing had to be slid up so that the part sticking out outside the roof was no longer sticking out. I have very sore knuckles on both hands as you have to grip the tube hard whilst sliding it up and at the same time you have to lift the roof of the tube with your knuckles or the pressure on the tube prevents it from moving. Tends to scrape the skin right off.

Just about every overlap on the North side needed to be reinforced this way, some only requiring one tube, others more.

There were also one or two sagging areas the were not overlaps and these were also reinforced. The bright area you can see on the right hand side of the picture is where part of the bitumen roof broke off as I pushed the tube through to the outside.

I could not prevent damage to the roof as you can see from this hole and in the previous photo, the material is just too fragile right now. I don't know how old the workshop is but it is in the order of decades rather than years. I suspect that it was built around about the same time as the house and is thus around 40 years old. The life of this roofing material if you buy it these days is a mere 15 years so it would seem that this roof is well past the expected lifetime.

But it will have to do for at least another 15 months.

Still, for around £50 I have found a workaround for the leaky roof (I hope) and we have plans for a new capping on the workshop for later in the year. If the roof sags in other places then I have a few tubes left over and they are easy to source if I need more.

But for now, a cup of tea, I think.