This is a time lapse video showing the reconstruction of an 8th century turf farmhouse at the Yeb Hettinga Museum in the village of Firdgum, Friesland, northern Netherlands:
Horses in a salt marsh in Lauwersmeer, Friesland (source).
In
the days before dykes, regular flooding prevented
trees from growing in the north of the Netherlands, so very
little wood was available to build houses. Starting around 400 AD,
houses there were built on artificial platforms to keep them out of the
flood water, and constructed of stacked clay turf blocks (turves). The walls of this house are a metre thick, which both insulates the house from the cold of the North Sea coast and supports the weight of the roof.
Most of the 8th century house collapsed due to a roof leak in 2013 and was
reconstructed starting in 2014 by volunteers, in coordination with the
University of Groningen.
You can see the exposed rafters of the turf house here. I'm guessing that's the museum building behind it, but I haven't been able to translate 'Yeb Hettinga Skoalle.' That might be in Frisian, not Dutch. (Photo by Daniel Postma)
The pre-collapse roof, replaced in the summer of 2013, was made of layers of sod and manure over wooden rafters, but the roof of the 2015 reconstruction is made of thatch over wooden rafters. I don't know why that might be.
The
[farm house], which is nearly 17 metres long, is characterized by a 1
metre-thick carrier wall made of layered turf, as was customary
throughout the region from the fifth to the early eighth century. It is
also the first archaeological reconstruction with an arch-shaped roof
construction, which clearly distinguishes it from the rectangular
trusses of existing historic farmhouses.
I couldn't find more than a couple progress photos of the reconstruction, just the video up top and a few casual photos on the Zodenhuis Project Twitter (mostly in Dutch), but I did find some good quality photos of a roof replacement done on the house in the summer of 2013 on the Zodenhuis Project Tumblr (in Dutch):
The rafters almost ready to be covered with sod (May 2013)
Applying cow manure mixed with straw over top of the turves to provide a waterproof layer (May 2013)
Manure being applied to the first layer of sod (May 2013)
"On the west side the roof of the sod house is now equipped with the first layer of turf. This side now awaits a layer of manure and two layers of sod." (June 2013)
The house after it re-opened to the public later in 2013:
The finished house. I think those dots are cow patties stuck to the walls to dry.
That little girl is even wearing wooden clogs. I'm guessing that's early medieval dress (Yeb Hettinga Museum).
Houses in prehistoric and early medieval Europe didn't have chimneys, so the smoke from the fire either drifted out through the door, if it was open, or just filtered out through the roof, like this thatched example in Ireland:
There's a bit more on early medieval Frisian turf houses and this house's construction at Daniel Postma's Tumblr, the Zodenhuis Firdham Facebook page (in Dutch) and Twitter (mostly in Dutch), the Zodenhuis Project Tumblr (inactive, in Dutch), but I've summarised most of it here. I found a couple academic articles in the links section of the project Tumblr, but I can't read Dutch and that's more than Google Translate can handle.