Adding and insulating the roof

Old buildings expert Marianne Suhr catches up with progress at Watts Barn and sees it reach a turning point as the new clay tiled roof goes up, insulated with an ultra thin but highly effective foil.

ABOVE: The main barn has been repaired and is ready for its new roof.

There are several major milestones in any large building project: gaining planning permission, getting the foundations in, sorting the drains, but I think the real psychological challenge is getting the roof on. Once the building is largely watertight, then the owners can sleep at night without worrying whether the tarpaulin has blown off or that rain has saturated the latest work. In this case, Heather and Graham, the owners of Watts Barn, could see their future home finally taking shape and began to visualise the space they’d live in more clearly.

For building surveyor Richard Cain, the design of the roof and its insulation was critical to the success of the finished building. Richard was keen to expose the old oak rafters (the sloping roof timbers) so that they could be seen from underneath within the house. To do this, all the insulation would have to be fitted above the roof structure, rather than the more usual system of fitting it between the rafters or underneath them.

Richard decided to opt for a multi-foil insulation quilt called Tri Iso Super 10. This is made up of sheets of foil, with thin layers of wadding and foam in between, with a thickness of less than 30mm. It is equivalent to 210mm of mineral wool insulation, but it doesn’t add extra height to the roofline. However, not all building control authorities will accept it so do check first before specifying it. The key thing is to make sure it is properly fitted and sealed so that the wind can’t get in underneath the edges.

ABOVE (left-right): Glazing bars are fitted for the installation of an atrium at the entrance to the barn; New cast iron guttering is put up.
BELOW (left-right): The roof is insulated with a multi-foil quilt, Tri Iso Super 10 (available from buildingmaterials.co.uk), laid on top of the rafters; The roofers finishing off the entrance atrium.

Following original lines
Luckily Watts Barn was in safe hands with roofer Fred. He was a very experienced tradesman who was able to think through the problems and find solutions. Most roofers like to make sure the structure is dead straight and the tiles are horizontally coursed. But Richard had fought hard to make sure the ancient timber barn retained all its character, including the wobbly roofline and undulating profile. So when it came to laying the tiles, Fred had quite a job on his hands.

When the corrugated sheeting and what remained of the old roof slates had been taken off the year before, the existing Welsh slates had been carefully set aside. But only a small proportion were in good enough condition to re-use, so Richard decided to use handmade Michelmersh clay tiles for the main part of the roof and save the slates for the side wing.

The final roof is a triumph; when the tiles have gathered a little moss it will look as though it has always been there. Meanwhile, the building is watertight and comfortably warm so Heather and Graham can begin to relax.

ABOVE: The tiles stacked ready for placing.

Which gutter?

Whatever gutter you choose, fitting them to undulating eaves at the base of the roof can be extremely tricky so choose a skilled fitter.

Cast iron: For a traditional feel choose cast iron available from companies such as J & JW Longbottom (01484 682141; longbottomfoundry.co.uk). Cast iron needs to be well decorated using a good paint system to minimise rusting. Set cast iron downpipes off the wall by at least 50mm to allow future maintenance and redecoration.

Cast aluminium: With the look of a cast iron gutter, but the ease of a rust free system, cast aluminium is an appealing option. Buy it powder coated (it’s available in many colours) to save time decorating on site. It is lightweight, requiring less support than cast iron. For examples browse Alumasc Gutter Systems (01744 648400; alumascrainwater.co.uk).

Copper or galvanised: For a contemporary touch, copper or galvanised gutters can complement an old house effectively. Try Coppa Gutta (0845 050 4590; coppagutta.co.uk).

ABOVE: Watts Barn’s finished roof is a harmonious blend of new handmade tiles and salvaged Welsh slates.

Read more advice from Marianne Suhr on planning a roofing project...

WORDS & PICTURES MARIANNE SUHR
Featured in the June 2011 issue of Period Living