Hi,

Recent posts about timber physiology and conversion were in my mind when Anne Ree called yesterday to tell me about a cottage that she had just viewed in Purley, Berkshire, England. She sent me a few digi pics to ask my opinion on certain matters and this was interesting since here was 400 year old testimony to past practice.



The first item to catch my attention was the gable end tie beam and I attach below a zoom in on this component.



This is an oak tie beam that has been halved and the pith or heart of the tree can plainly be seen wandering along the timber. The tree used to produce this component was obviously not very old maybe 30 - 50 years and so this must be made up from a high proportion of juvenille wood which we would expect might result in significant warp and decay but the proof is here that a timber that might well be classed as substandard today has endured in exposed service for at least 400 years. The secret to long term survival is of course the ability to dry quickly. The same cannot be said for the cross braces which have been covered by tiles. With a bit of luck these will have been attached with lime mortar which might help to remove any trapped water but the same cannot be said for the two rendered gable panels where portland cement has been employed. This is going to result in frost and water trap damage to both the timbers and the underlying soft red brickwork.

I was recently challeged hard on this forum as to how I can be so sure of my opinions in respect of timber framed buildings and the answer might well lie in having the opportunity close to home to examine the long term effects of design, function, tansformation, materials and workmanship where these factors can be observed first hand and conclusions drawn as to effectiveness in respect of all these factors.

This particular frame reflects function in the determination of bay lengths. We can see that a short 6 - 8 ft bay has been employed in which the chimney is currently located. This could be a smoke bay which would predate the insertion of a chimney or it could have been built from new to accomodate a chimney. The LH bay length is about 10ft and the RH about 12 ft. This building is equipped with sills and Anne tells me that these are now somewhat deteriorated. A scotch (dap) is visible in the main post to the LH of the porch at mid rail height and this indicates that this building has probably already had work done to repair or replace the sill and also right the building. Some of the infill horizontal noggin is not positioned in a regular fashion and this is most likely a cheap and chearful repair done by a brick layer rather than carpenter. The quality of timber used for the mid rails is pretty awful and the mortices at their connection with the main posts have now blown to reveal the under lying tenons. Despite this the building has survived long term and this can also be attributed to the large number of secondary timbers that were employed initially to frame windows, doors and infil panels which also help to provide secondary load paths to accomodate failures in main components. All the lesons needing to be respected to ensure the long term survival of a timber framed building are here for those who want to see them.

The height from the mid rail to top of wall plate indicates that this is not an open hall and was built with upper floors from the outset. We can thus probably confidently ascribe a date of later than 1550 but probably no later than 1600. The porch is positioned in front of the chimney bay and there will be a short entrace lobby immediatly behind the front door and a stair winding up the chimney on the far side. This style of house would thus be called a lobby entrance box frame.

I suppose if one see's enough of these kinds of buildings then eventually one becomes quite intuitive about what to expect and so here we have a building pattern that can be replicated with fairly good certainty of long term performance and with little risk accrueing to a carpenter builder even if he has to use sub standard materials and is unable to run calculations.

The result also just happens to be quite charming.

Regards

Ken Hume