Prescot THI Blog

21 Eccleston Street: Discoveries

Almost a year after my blog entry about the people 21 Eccleston Street, here is a summary of what we have found out about the building so far.

During the repair, restoration and conversion works the modern elements of the interior were peeled away, and we could start to see the two ‘halves’ of the building, the brick built late Georgian / early Victorian part and the circa 1600 timber framed part.

You’ve Been Framed: The Old Part of the Building

Much of the timber framing to the outer walls of the building is either concealed within brickwork and plaster or may have been removed during 20th century repairs and renovations. What we can see in what is the kitchen to Flossy’s is some large oak floor joists that are supported by a very large oak beam that is itself supported at either end by timber posts that are buried in the front and back walls of the kitchen.

The long beam that runs the full length of the kitchen at Flossy’s carries the joists of the floor above. The furthest end of the beam is carried on a vertical timber post buried in the wall.

The long edges of the oak beam and the joists were chamfered off to give a more pleasing visual effect, which suggests this ceiling was originally exposed timber until at some point in the past when nails were driven into the timber so that a lath and plaster ceiling could be inserted. Alas fire regulations and the need for sanitary conditions in this commercial kitchen mean this has all be covered up again, but at least we now know what is there, it has been recorded and repaired as necessary.

For such a small building the brick chimneybreast is remarkably large, but this might well be because it was seemingly added after the timber frame was already there. The chimney had to be freestanding when it was built and this is probably why it is so wide and deep, taking up a big chunk of the back rooms at ground and first floor. The stub of the chimney above roof level has been raised to its former height as part of the THI-funded works.

This chimney was raised up from being a stub that barely poked through the roof and is now its former height. See how the chimney is not at the very edge of the roof? This could well be because the brick chimney was built inside a timber frame that was erected before the brick chimneystack was built.

Up at first floor, the ceiling here is again wide floorboards carried on oak joists which are supported along the middle of their span by a spine beam which is itself carried by beams that are supported at either end by timber posts that are half-buried in the walls. Unlike downstairs the edges of the joists and beams are not chamfered. This could either be because there was a lath and plaster ceiling here from the start (with the beams plastered over) or this was a lower status room and so is was simply left bare and undecorated.

The timbers of the first floor ceiling are much more of a jumble than the beam and joists at ground floor (see the first photo of this blog, above). The main structural beams run at ninety degrees to the floor below and rather than one big beam there are two slightly thinner ones.

The timbers in the first floor ceiling certainly are a mixed bunch – this one has the notches and peg holes of mortice and tenor joints that are proof of the timber serving another purpose previously, perhaps as a upright wall post. (My apologies for the blurry photo).

Wasp Happening / Appetite for Destruction

In both the ceiling / floor structures at first floor and loft level there has been some timber replacement in the past, some conservative repair, but also, unfortunately, timber that is beyond repair and must be replaced. This is the case for many of the attic floorboards, and in places some of the joists have had a wood wasp infestation for a long time. Several of the timbers had lost a lot of their thickness and the remaining bits of wood in and around this are like honeycomb, as they are riddled with small boreholes.

I’d heard of wood worm before, but not wood wasp. A bit of reading up revealed that the female wood wasp (or horntail as they’re also known) physically bores into wood and injects an egg into it. If she finds a suitable tree or bit of timber she will inject several eggs. These eggs hatch into larvae that chomp through the wood for several years and eat all the way to the underside of the bark. They then retreat back in to the wood, form a cocoon, emerge as a wasp, eat through the final thin skin of wood they left previously, and then they’re off.

After a few years of eating a historically and architecturally significant building, I guess the natural next thing for the wasp to do is to go and spoil a picnic or drown in a glass of lemonade, but enough of them do manage to reproduce and start the cycle again.

Born this way / Some Mothers Do ‘Ave ‘Em: some of the timbers that were so badly eaten by wood wasp larvae that they were too far gone to safely re-use.

Apparently wood wasps usually prefer pine trees that are a bit unhealthy (but boring through the bark will still be tough work, surely?), but the effects of their life cycle are found in building timbers all over the country. I suppose this is an example of a wild animal taking up the opportunities that our manmade towns and cities present. Although the oak timber frame will be a denser timber than pine, I guess on balance the lack of bark on these joists and beams makes it possible for the horntail to bore into it and inject its eggs. All of the timber at 21 Eccleston Street, old and replacement, has been treated for infestation.

Wood wasps can find their way in and out of a building through a single tiny gap in the masonry or roof, and the wasps and their larvae can be there in a concealed part of the ceiling, floor or roof, without anyone occupying the building having any reasonable way of knowing about them. This will be how in this case the wasps got away with doing so much damage without it impacting at all the day to day business of the building’s occupants.

Brace Yourself, There’s More. Truss Me

It’s mind-blowing to think this oak roof truss has been here for around FOUR HUNDRED YEARS! This is a king post truss: the king post is the stout post in the middle. To either side of is are diagonal struts which support the ‘blades’ of the truss. The tie beam can just about be seen running left to right underneath the king post and struts.

Moving upwards to the roof, apart from a couple of conservative repairs in replacement timber, there is a lot of the original roof timber still in situ. In the centre of the roof is a king post truss made of thick pieces of oak. The truss is the main structural component of the roof that supports all of the purlins (the long thick timbers that support the roof slope at its midpoint) that in turn support all of the rafters (the thin timbers that form the shape of the roof) that in turn carry all of those slates. It is named for the central vertical ‘king’ post that reaches the apex of the roof. The king post is joined on each side by sloping ‘blade’ that follows the slope of the roof. Below the king post and each of the blades is a long horizontal tie beam that extends across the full width of the bottom of the roof. It is called a tie beam because it helps to ‘tie’ the tops of the walls together, making for a stronger, more rigid building. Further rigidity is provided by the short but thick timbers that run diagonally between the principals and the purlins. These are called wind braces (one of my favourite architectural terms!) and their job is to stop the truss racking or toppling sideways, which would be more likely in high winds.

An unusual feature and a possible source of additional stability is the binder that runs from the middle of the tie beam. It appears to have acted as a spine for the attic floor joists, as there are regularly spaced bevelled pockets to receive the ends of floor joists.

Inside the triangular shape of the roof truss there are struts: diagonal timbers that add a bit more stability to the truss. Amazingly in one half of the truss there is surviving (original?) wattle and daub panel. Timber framed buildings were just that – timber frames, the spaces in between the pieces of frame needed to be filled in with something to keep the wind and rain out or to divide the interior into rooms. A commonly used infill, particularly where brick and timber were either unavailable or too expensive was to weave a mesh of thin branches (the wattle), slot their ends into the structural timber and to then plaster this mesh with a clay-earth-straw-and sometimes-dung-urine-or-blood mix (the daub).

The wattle and daub infill panels in the roof truss, which was presumably added so that the loft space could be used as two rooms. If you scroll up and look at the previous photo – one of the panels (and part of the strut) is missing because a long time ago someone put a doorway in truss! It is probable that when this timber frame was first built, its outer walls also had wattle and daub panels like this.

Over time, particularly as brick became cheaper and more commonly used, wattle and daub was stripped out of frames and the gaps infilled with brick. Also wattle and daub would need periodic replacement due to it being not especially durable. And of course, many timber framed buildings were simply torn down all together and replaced in new masonry buildings. These three reasons are chiefly why it is very rare to find surviving wattle and daub anywhere. This makes the surviving section in 21 Eccleston Street of particular interest.

As part of our works we have left the principal roof timbers undisturbed. Much more and better-written info about Wattle and Daub here.

Rot ‘n’ Roll

After all that old joinery, the part of the building that is merely 183 or so years old seems far less interesting in comparison!

It roof is a much simpler construction: a principal rafter roof where the rafters are jointed at the apex and are trenched into the biggest components of the roof: purlins that rest on brick walls at either end. This is a very economical roof construction, as it requires the fewest large timber members, but to be fair a large number of big heavy timbers are not necessary to span a room’s width with brick gables at either side. I have seen similar roofs at THI buildings like 44 Eccleston Street (mid-18th century?) and 13-15 Atherton Street (1770s).

Compared to the large timbers in the older part of the building, the ones in this part of the building are much more regular and slimmer. The ceiling was replaced some time ago, with the ceiling joists (mostly modern timber) attached to timber hangers that have been nailed to the rafters. A similar roof is in situ at 44 Eccleston Street.

The nineteenth century roof structure is made of much thinner timbers than its older neighbour. The biggest timbers are the purlins that rest on the brick gable walls and run the full width of the room. These purlins carry along their length the rafters that form the slopes of the roof. The rafters are in pairs that are pegged together where they meet at the top of the roof structure. From each pair of rafters there is a pair of timber hangers to which the joists for the ceiling are attached. The hanger and ceiling joists make the roof look far more complicated than it actually is. Take these away and the structure is minimal.

While the roof structure is economical, the front wall is one-and-a-half bricks thick to provide additional stability and I guess to give the wall more thermal mass (i.e. to keep the heat in during winter). This brickwork (and the roof it carries) rest on the beam over the shopfront.

What seems to have happened is that the original or historic beam over the shopfront was replaced with three pieces of thinner timber lashed together to form a ‘composite beam’. This composite beam might have been inserted in the 1960s when the shopfront was modernised or around 1980 when there was a building improvement grants scheme operating in Prescot, which is when much of the now-removed shopfront dated from.

What then happened is 30 to 50 years of the front gutter becoming blocked, leaking or otherwise not draining properly. Rainwater therefore found its way into the brick wall and through gravity reached one end of the composite timber beam over the shopfront. This end of the beam then started to rot due to the dampness of the wall. As it rotted it appears to have lost strength, causing movement in the brickwork above, plus the beam also appears to have rotated forward as it rotted, pulling with it the bricks sat immediately on top. This caused visible cracks through the bricks to appear and I am sure this got worse since I started working in Prescot in 2013.

Here is the cracked brickwork prior to repair. It takes a lot of pressure for bricks to crack through like that…

The solution has been to replace the modern timber composite beam with steel beams and to rebuild the brickwork above. This is very similar to the work done at 44 Eccleston Street as part of the THI, but in that case the beam underneath was sound – it was the brick wall that was one the move because it was not well tied-in to the rest of the structure.

The new red steel beam for the shopfront had the old brick wall rebuilt on top of it using the same bricks to match the original coursing. Note the thickness of the wall: one and a half bricks.

All that work and expense due to one defective gutter! It brings the SPAB / IHBC ‘A Stitch In Time’ home maintenance guidance to mind…

…and here’s the offending gutter – blocked – before works began.

Reaching the ground floor, it is remarkable how the shop floor of the Georgian part of the building is so high ceilinged. The floor level steps down considerably between the timber framed part of the building and the Georgian part, though the floor upstairs is level throughout. The shop would have been very light and airy when built and our restoration to the shopfront has brought these qualities back to the room.

Here is 21 Eccleston Street last summer – front wall rebuilt, most of the new shopfront installed, roof re-laid and windows refurbished. The final stage of the shopfront works will happen very soon!

The THI-funded works will finish at 21 and 23 Eccleston Street soon and no doubt I will be posting a blog about the completed projects.

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