# Outbuilding conversion



## HexusOdy (5 Aug 2019)

In the coming months I will take over an outbuilding at my in laws as a workshop. Because I lost my garage to a domestic conversion and the in laws owe me for various jobs I've done for them 

It needs a lot of work to make it functional. Much of it is cleaning but it also requires a new floor (currently some uneven brick thing) and insulating, which is my question for today.

The current roof is a standard clay pantile roof and as a barn built a 100 years ago or more it didn't require felting. As many of you know pantiles are generally good for keeping rain out, not so much for wind and dirt that comes in horizontally. Having had a garage workshop that was pretty unusable in winter I want to make sure this one is warm and dry.

Any ideas for keeping out unwanted water (from bad storms) and keeping the heat in? I've thought about felting some OSB then nailing that to the underside of the rafters. But there would be joints I can't tape from above and water has a habit of going just where you don't want it to. 

Foil backed celotex is a similar option, I can take it underneath as usual but again there is the chance water could get into the joints from above, although I think the celotex would handle it better than OSB. 

Any ideas or practical experience with this?


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## kevinlightfoot (5 Aug 2019)

If it's not too large a building I would remove the tiles,over board the roof and then felt and tile using the old tiles,not too big a job and at least you know it will be dry.You can then safely insulate later in the surety you won't have any problems.A bit more labour involved but that's the way I would go,call in some favours to perhaps get some help.


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## Fitzroy (5 Aug 2019)

Or if it’s huge could you not build a building within it. Basic timber frame, with insulation and a mono pitched roof just to handle any wind blown rain. The outer building just becomes a rain skin. 

Just spit balling ideas. 

Fitz.


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## Lons (5 Aug 2019)

I'd probably do what Kevin suggested if it was mine although there's always a chance you'll break a few of the tiles so need some spares. If the barn is empty then it's relatively simple.

If the roof is sound you could have it sprayed with foam which not only insulates but seals the roof. The only drawback I know of is that if you did get a broken tile in future it's more of a pain to replace but it does reduce the chance of being broken in any case.

I don't know of a DIY method of appying the foam and it won't be cheap, we had it done to a grade 2 listed stable block conversion with slate roofs about 15 years ago and to the best of my knowledge it's worked perfectly to date.

I'm sure Mike will be along shortly to offer expert advice.


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## HexusOdy (6 Aug 2019)

I don't think reroofing is an option. It's pretty large, approx 20 x 20 but has a pretty good pitch on it too. I'd say the ridge is a good 20ft up. It's also hipped, so not only do I have the front and back pitch but one side pitch too (I don't have the whole building). 

I could quite easily build an internal ceiling for heat and dirt insulation and still have a healthy ceiling height, but that wouldn't help me with water which is my biggest concern. 

I suppose I could build the sub roof with access so I could get up there and board and seal it after, but then it's a big span, if I have to make it weight bearing so I can get up there and work it's a whole different and more expensive ceiling construction and might work out just as expensive as spray foaming it.


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## topchippytom (6 Aug 2019)

Roof spray insulation foam is your best bet ,Just enter that into youtube and you will see how it works


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## HexusOdy (6 Aug 2019)

Yes been looking at the spray foam since it was suggested above. Anybody have experience with it?

It's not cheap, but there are DIY kits available. Apparently it's tricky to do, but as this is an old barn roof for a workshop and not a 500k detached new build I don't suppose it matters much if I'm a bit uneven in spots or make a bit of a mess.


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## topchippytom (6 Aug 2019)

HexusOdy":19pvvj7r said:


> Yes been looking at the spray foam since it was suggested above. Anybody have experience with it?
> 
> It's not cheap, but there are DIY kits available. Apparently it's tricky to do, but as this is an old barn roof for a workshop and not a 500k detached new build I don't suppose it matters much if I'm a bit uneven in spots or make a bit of a mess.


I stripped a roof for re slating that had the foam sprayed under the slates and all be it a pain in the backside to strip the foam really was good stuff.


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## Lons (6 Aug 2019)

The stables we did were more than 3 times the size of yours and in those days it definitely wasn't a DIY job, we also needed to be careful as the building was grade 2 listed and being converted into a large house.

It's a messy job and the guys were fully suited and masked up, the foam can never be even but as long as it's thick enough to meet the insulation values you want and sprayed into every corner it makes an excellent job.
Ours as I said was slate, no underfelt and was basically sound though we did need to replace / re-fix some slates. If you can do it yourself at a reasonable price then it's probably the way to go. I don't see how it's possible to build any kind of internal ceiling successfully if you have water coming through the tiles which is always going to cause problems.


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## HexusOdy (7 Aug 2019)

Lons":vedhnde6 said:


> The stables we did were more than 3 times the size of yours and in those days it definitely wasn't a DIY job, we also needed to be careful as the building was grade 2 listed and being converted into a large house.
> 
> It's a messy job and the guys were fully suited and masked up, the foam can never be even but as long as it's thick enough to meet the insulation values you want and sprayed into every corner it makes an excellent job.
> Ours as I said was slate, no underfelt and was basically sound though we did need to replace / re-fix some slates. If you can do it yourself at a reasonable price then it's probably the way to go. I don't see how it's possible to build any kind of internal ceiling successfully if you have water coming through the tiles which is always going to cause problems.



Thanks Lons. Out of interest how much did your building cost to spray foam?


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## Lons (7 Aug 2019)

I'd have to look and my records are archived but might take some finding now. Off the top of my head it was around £3k and that was 14 or 15 years ago but was cheaper than a strip and replace as we needed insulation as well, bedrooms had vaulted ceilings / exposed beams.
Also meant that as the roof remained intact we had no bad weather issues and could get on with the internal walls and floors without concern.

I was surprised at the time that the planners allowed us to do it to a listed building but they were quite happy.

I think the system is more common now so hopefully prices are better.


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