Timber beam-end engineering repairs - Resin bonded cross (continued)

Click on any of the images for a larger view.

Next a cut was made to separate the TRS from the post. This is a very crucial point. If the roof had not been adequately supported the cut will close up.

Once the length of the post had been established, we could cut the post.

Due to the internal scaffolding platform position, we could not go down the post sufficiently to complete all the slots in one elevation, so on the reverse side we cut out the post to accept the TRS steelwork.

Drilling out procedure.

Slot ready to be finished by hand with a chisel.

Open view of all the cut offs.

Now that the full length of the repair system was known the TRS was cut and a first dry fit established. Note the gap at the top of the TRS (reason explained later).

Next the TRS post was marked out to form a horizontal cut out, to fall in line with the purlin slots.

Post cut out and in line with purlin slots. You can see within the post slot the inset bars that form the connection bond to the parent post.

The connection bars are dry fitted, two bars in total. 'Nice fit'. You may also note the air relese holes now drilled into the top of the parent purlin.

Next job was to line the top of the TRS up with the upper post cut outs.

The TRS was end grain drilled out, and a thixotropic epoxy resin injected into the holes. Fibre rods were inserted into the resin.

The problem with this installation was that I needed the resins to stay in place whilst the system was assembled. This was achieved by the use of a thixotropic resin. The resin was injected firstly along the back edge of the post, and then gradually inserted into the slots.

Resins partially filling the cut outs. Note no loss of resin.

TRS is offered to the upper post cut out.

Additional resin is then injected to fill the slots.

When the TRS was offered to the post there was a gap of about 6 mm between the two timber faces. This allowed additional resin to be injected to form a fully bonde seal. The resin injected earlier to the back of the post face was to prevent loss of resin at this stage.

A plastic shutter was placed over the resins, with a releasing agent to allow removal. The joint between the two faces was cleaned off.

With the top section of the post 'bonded' the next problem was to form a box shutter to infill between the post and the purlin cut offs.

These were made from plywood and would remain in situ. The open top of the box would act as a pouring reservoir to fill slots created in the post and purlins. You may notice a shelf bracket under the resin box. This is mainly to hold the weight of the resins.

The slots are sealed and covered with a plastic shuttering with a releasing agent.

Rear elevation view, showing boxing and lower TRS joint.

Once fully sealed the reservoirs were filled, allowing the resins to run along the slots. Not a bit of resin pushed out of the air hole.

"That's it - now do another five!"

Finished job - detail.

Fully viewed.